PhotoDemon 6.0 beta is live

Chroma key (green screen) is one of many new tools in this release.
Chroma key (green screen) is one of many new tools in this release.

Download

Remember: if you’re an advanced user, you never have to wait for a beta release. You can always download PhotoDemon’s latest development release from its GitHub page (source code), or from this nightly build permalink (program only).

PhotoDemon is funded by donations from users like you.
Please consider a small donation to fund development and to help me support my family.
Even $1.00 helps. Thank you!

Overview

It’s taken nearly six months, but PhotoDemon 6.0 is finally ready for release. I’ve already talked about some of the great features this release includes, like powerful selection tools, metadata (EXIF) support, Curves and other new tools, so I’d recommend glancing through the linked article if you’re curious.

Since that article, a number of other features have been added or improved:

  • All tools now support save/load presets, reset to default, randomize, and automatic save/load of last-used settings. These items are all accessible from a new “command bar” at the bottom of each tool dialog.
  • From left-to-right, the command bar includes buttons for: reset, randomize, saved presets, and save current settings as preset.  Last-used settings are automatically saved and loaded by the dialog.
    From left-to-right, the command bar includes buttons for: reset, randomize, saved presets, and save current settings as preset. Last-used settings are automatically saved and loaded by the dialog.
  • Three new blur tools: motion, radial, and zoom blur. These tools outperform similar tools in GIMP and Paint.NET.
  • PhotoDemon's new radial blur tool is 4x faster than Paint.NET's, and 30x faster then GIMP's - and at high angles, it produces significantly better output.
    PhotoDemon’s new radial blur tool is 4x faster than Paint.NET’s, and 30x faster then GIMP’s – and at high angles, it produces significantly better output.
  • Much faster Gaussian and Box blur tools (20x improvement!)
  • The updated Gaussian Blur tool now provides quality settings for improved performance.  For most photos, the difference between "good" and "best" will be indistinguishable, but "good" will be some 20x faster.
    The updated Gaussian Blur tool now provides quality settings for improved performance. For most photos, the difference between “good” and “best” will be indistinguishable, but “good” will be some 20x faster.
  • A new chroma key (“green screen”) tool with performance comparable to professional tools, including full support for edge blending. Find it in the Image -> Transparency -> Make color transparent menu.
  • Before color removal; image courtesy http://dimula73.blogspot.com/2013/03/new-user-interface-for-krita-color-to.html
    Before color removal; image courtesy http://dimula73.blogspot.com/2013/03/new-user-interface-for-krita-color-to.html
    After color removal.  Note that the tool creates a 32bpp image, which you can then composite using any photo editing software.
    After color removal. Note that the tool creates a 32bpp image, which you can then composite using any photo editing software.
  • A new Language Editor makes contributing new translations fast and easy.
  • The new Language Editor makes it easier than ever to get involved in translation.  Please contact me if you can help!  (You will receive full credit for your work.)
    The new Language Editor makes it easier than ever to get involved in translation. Please contact me if you can help! (You will receive full credit for your work.)
  • New variable-strength Sharpen tool
  • Previously, PhotoDemon only provided set "Sharpen" and "Sharpen More" functions.  The new tool allows for floating-point adjustments, which allow for much more nuanced fixes.  (Unsharp Masking is still available too, obviously!)
    Previously, PhotoDemon only provided set “Sharpen” and “Sharpen More” functions. The new tool allows for floating-point adjustments, which allow for much more nuanced fixes. (Unsharp Masking is still available too, obviously!)
  • New Oil Painting tool
  • Same photo as the screenshot at the top of this page, but oil-ified.
    Same photo as the screenshot at the top of this page, but oil-ified.
  • Minor improvements to many tools, including polar coordinate conversion, perspective correction, wave distort, ripple distort, figured glass, tile image, posterize, rotate, custom filters, histogram.
  • The perspective tool now supports both forward and reverse transforms.  Reverse transforms allow you to simply trace a crooked object, and have it automatically straightened by the program.
    The perspective tool now supports both forward and reverse transforms. Reverse transforms allow you to simply trace a crooked object, and have it automatically straightened by the program.
    The histogram offers new render options, which can be helpful for identifying areas of channel overlap.
    The histogram offers new render options, which can be helpful for identifying areas of channel overlap.
  • Any tool with a “color” option now allows you to pick a color directly from the image by clicking the preview.
  • Much better support for high-DPI screens, including tablets.
  • Faster viewport rendering for 32bpp images.

Again, these new features are only a fraction of what 6.0 includes. Please check out the 6.0 preview article for news on all the other new tools and improvements.

Acknowledgments

This 6.0 release represents six months of hard work from a variety of contributors. While I am very grateful to all of PhotoDemon’s talented contributors, a few deserve special mention. Thank you to:

  • Audioglider for contributing three new tools: Channel Mixer, Vibrance, and Exposure. Audioglider also reported a number of issues, and motivated me to implement preset support for every PD tool.
  • Frank Donckers for again providing the German, French, and Dutch translations, and for contributing many pieces of code to the new Language Editor, including the Google Translate interface. Amazing stuff.
  • GioRock for the Italian translation, and for detailed testing of many small translation items. It takes a ton of work to get all of PD’s text translating properly, and GioRock debugged many items for me, which benefits users of every language.
  • Kroc Camen for a new IDE-safe mouse interface class, derived from his own open-source VB project. Kroc also reviews many of PD’s individual commits, where he catches many small items I overlook.
  • Robert Rayment for helping me profile and optimize a number of PD’s more taxing functions, and for many suggestions on tweaks and improvements. Many of the performance improvements available in this new version are a result of Robert’s help. Please check out his own VB image editor if you can.

Known bugs

  • EXIF data is not maintained with certain combinations of preferences (delay loading EXIF + export full data when saving). This is caused by a metadata caching issue, and will be fixed by release. Fixed!
  • ExifTool plugin is slightly out of date. It will be updated to its latest version upon 6.0’s release. Fixed!
  • Metadata menus sometimes become disabled even when metadata is available. This will be fixed by release. Fixed!
  • OK and Cancel buttons are not currently translated. This will be fixed by release. Fixed!
  • Some hotkeys don’t fire unless the main form is first clicked. This is a known problem with VB, and will hopefully be fixed by release. Fixed!
  • Master language file is missing a few minor text entries. This will be fixed by release.

The beta version was released before these small items were fixed, so it still contains these bugs. Developers can download updated source code, with these fixes, from GitHub.

Official release timeline

Barring any major bugs, the official 6.0 release should happen within several weeks. Feature-wise, it will be identical to this beta release. The only changes will be minor bug fixes and performance improvements. Automatic update notifications for existing PhotoDemon installs will also go live at that point.

How to compile zLib 1.2.8 (WINAPI / WAPI / STDCALL version)

This is not a full-blown article – just a quick HOWTO for people who require the latest version of zLib and want to use it from a language (like classic VB) that requires a standard WinAPI interface.

By default, zLib uses C calling conventions (CDECL). Gilles Vollant has helpfully provided an STDCALL version of zLib in the past, but his site only provides version 1.2.5, which dates back to January 2012. zLib is currently on version 1.2.8.

Gilles has contributed his WAPI fixes to the core zLib distribution so that anyone can compile it themselves. To do this, you will need to download:

Once both of those are downloaded (and updated, as VS 2012 will require you to install several service packs), follow these steps to compile zLib yourself:

  1. Extract the entire zLib file and navigate to the /contrib/masmx86 folder. Open the “bld_ml32.bat” file in a text editor.
  2. Add the “/safeseh” switch to both lines in that file (e.g. “ml /safeseh /coff /Zi /c /Flmatch686.lst match686.asm”). Then save and exit.
  3. Navigate to the /contrib/vstudio/vc11/ folder. Open the zlibvc.sln file in your newly installed Visual Studio 2012 Express.
  4. In the Solution Explorer (top-right by default), right-click “zlibstat” then select “Properties” at the bottom.
  5. Go to Configuration Properties -> C/C++ -> Preprocessor, and in the Preprocessor Definitions line remove “ZLIB_WINAPI;” (don’t forget to remove the trailing semicolon).
  6. Now, we need to fix a recently introduced problem that relies on Win8 functionality. In the Solution Explorer, navigate to zlibvc -> iowin32.c. Double-click to open the file.
  7. Find the line of text that reads “#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP)”. Change this line to “#if WINAPI_FAMILY_ONE_PARTITION(WINAPI_FAMILY_DESKTOP_APP, WINAPI_PARTITION_APP)”. (Thanks to this link for this fix.)
  8. zLib uses a Version number declaration that can cause the build process to fail. To fix this, go back to the Solution Explorer, then navigate to zlibvc -> zlibvc.def. Double-click to open.
  9. Change the line that reads “VERSION 1.2.8” to read “VERSION 1.28”.
  10. Finally, go to the Build -> Configuration Manager menu and change the Active Solution Configuration to “Release”.
  11. Exit that window and press F7 (or click the Build -> Build Solution menu). The project should successfully build.
  12. You can find your newly compiled zlibwapi.dll file in the /contrib/vstudio/vc11/x86/ZlibDllRelease/ folder.

PhotoDemon 5.4 Beta Now Available

  1. Summary
  2. Download
  3. List of what’s new and improved
  4. Known bugs

Summary

PhotoDemon 5.4 is nearing completion, and I need help testing it. Version 5.4 provides a bunch of new features, including French, German, and Dutch (Flemish) language support. If you can help translate PhotoDemon into another language, please let me know! The translation process is very simple, and it requires no programming experience or special software.

Version 5.4 also includes nine new distort tools, tons of new file format features including specialized PNG and JPEG optimization, improved memory management, a new plugin manager, real-time Gaussian, Smart, and Box blur tools with variable radius, a full Unsharp Mask tool, vignetting, median filtering, adding film grain, automatic cropping, contour tracing, a new Batch Wizard, redesigned tool interfaces, and more. Please download the beta and let me know if you find any bugs.

Download

The PhotoDemon 5.4 beta comes in two flavors:

Remember – if you are an advanced user, you can always download the most recent development build of PhotoDemon’s source code from its GitHub page.

PhotoDemon is funded by donations from users like you.
Please consider a small donation to fund development and to help me support my family.
Even $1.00 helps. Thank you!

List of what’s new and improved in v5.4 (so far)

  • Official support for multiple languages. This is the biggest addition in version 5.4, and I can only claim partial credit for it. Primary credit goes to Frank Donckers, a fellow VB programmer and the one who prototyped the initial translation engine. Frank also supplied the translations for French, German, and Dutch (Flemish), so I owe him an enormous debt of gratitude.
  • Vastly improved file format support. JPEGs now support automatic EXIF rotation on import, and a variety of options on export (Huffman table optimization, progressive scan, thumbnail embedding, specific subsampling). TIFF exporting supports CMYK encoding and a number of compression schemes (none, PackBits, LZW, CCITT 3 and 4, zLib, and more). PNG exporting supports variable compression strength, interlacing, and background color chunk. PPM exporting supports RAW or ASCII encoding. BMP and TGA now support RLE encoding. For ICO files, all icons inside the file can now be loaded (instead of just the first one).
  • Nine new Distort-style tools. Add and remove lens distortion. Swirl. Ripple. Pinch and whirl. Waves. Kaleidoscope. Polar conversion (both directions). Figured glass (dents).
  • New and improved standard tools, including Box Blur, Gaussian Blur, Smart Blur, and Unsharp Masking. Each of these functions now supports variable radii (up to hundreds of pixels), and all have been heavily optimized. Gaussian Blur is the fastest VB-only true gaussian ever written. (Not a joke.)
  • Tons of new tools, including Film Grain, Color Balance, Vignetting, Autocrop, Median, Modern Art, Trace Contour, Shadow/Midtone/Highlight, Monochrome -> Grayscale conversion, Film Noir, and Comic Book. All tools include real-time previews. A number of existing tools received big updates as well – particularly Gamma Correction, Dilate, Erode, Monochrome Conversion, and Printing.
  • New Batch Process wizard. This replaces the old Batch Convert tool, which was an interface nightmare. The new tool supports a number of new features, including drag/drop support of batch lists, live image previews, and tons of file renaming options (prefix, suffix, case conversion, removing text, conversion of spaces to underscores for web).
  • Universal color depth support at import and export time. PhotoDemon can now write 1, 4, 8, 24, and 32bpp variations of every supported file format. Color depth detection is automatic at save time – the program will count the number of colors in an image and automatically save to the most appropriate color depth. Alternatively, you can set a preference to manually specify color depth at save time. This also works for grayscale images; for example, the JPEG encoder will now detect grayscale images and write out 8bpp JPEGs accordingly. Alpha thresholding is also available when saving 32bpp images to 8bpp (e.g. PNG to GIF).
  • New pngnq-s9 plugin for optimizing PNG files. Pngnq-s9 is an optimized and feature-rich variant of the original pngnq optimization library. Pngnq-s9 works by converting 32bpp PNG files to 8bpp with a heavily optimized palette, including support for variable alpha channels. File size savings of over 50% are common. See the Options -> Plugin Manager -> pngnq-s9 menu for a full list of tunable parameters.
  • New plugin manager and plugin downloader. Plugins can now be individually enabled/disabled, and missing plugins can be automatically downloaded. All plugin installation and activation/deactivation can be applied without a program restart.
  • Many canvas and interface improvements. Larger effect and tool previews. Persistent zoom-in/zoom-out buttons. Image URLs and files can now be directly pasted as new images. Improved drag/drop support, including drag/drop from common dialogs. New “Safe” save behavior to avoid overwriting original files. New Close All Images menu. New algorithms for auto-zoom when images are loaded, meaning much better results at all screen sizes. Tool and file panels can now be hidden. Higher-quality dynamic icons for the program, taskbar, child windows, and Recent Images list. Improved support for low screen resolutions.
  • Many performance improvements. More aggressive memory management means lower resource usage. Program loading has been heavily streamlined, and now happens in less than a second on modern hardware. Image loading is much faster and more robust, including better support for damaged or incomplete image files.
  • Much more robust and comprehensive error handling. When loading multiple images, the program will now suppress warnings and failures (such as invalid files) until all images have been loaded. Many subclassing issues have been resolved – so no more surprise crashes! Overall this release should be extremely stable.
  • Many miscellaneous bug fixes and improvements. For a full list, see the commit log at https://github.com/tannerhelland/PhotoDemon/commits/master

Known bugs

Here is a list of known bugs with the current beta. These bugs will be fixed before the final release.

  • When a new language is selected, some text may not be translated. This is not a problem with the translation engine – it is a problem with the translation files, which are still being finalized. All text will be translated in the final release.
  • When using a language other than English, some text may overflow its boundaries or disappear off the page. This is a known problem that is still being worked on. All text – in any language – should fit properly in the final release.

Coming to PhotoDemon 5.4: Language Support. Translators welcome!

Today I made an interesting discovery: my PhotoDemon release dates are slipping further and further apart.

  • PhotoDemon 4.3 – 10 August 2012
  • PhotoDemon 4.4 – 21 August 2012 (11 days later)
  • PhotoDemon 5.0 – 21 September 2012 (31 days later)
  • PhotoDemon 5.2 – 28 November 2012 (68 days later)
  • PhotoDemon 5.4 – …? (76 days and counting)

If I throw together a quick chart for the delay between releases, a clear trend emerges:

Not my favorite correlation...
Shame on me…

According to the chart, I still have a good for or five months available to work on the next release…

Actually, PhotoDemon 5.4 is rapidly nearing completion! My excuse for this latest delay is a good one, and I imagine you already inferred it from the title of the article… but in case you didn’t:

The next PhotoDemon release will include support for multiple languages, with French, German, and Dutch (Vlaams) officially supported at release.

Language support has been a monster to implement on account of the large amount of text in the project, not to mention classic VB’s utter lack of usable translation libraries. As a result, an entirely novel language engine was written from scratch, with (quite lovely) XML files being used to supply the actual translation data.

To give you an idea of the scope: as part of the translation process, I wrote a separate program whose sole purpose was to extract all necessary text from the PhotoDemon source code so that a “master” language file could be assembled. According to it, PhotoDemon contains almost 1400 unique phrases, with a total of more than 7800 words. Every one of those phrase occurrences needed code added to handle the actual text substitution, and then there’s the obvious challenge of the translation itself.

Fortunately, I didn’t tackle this project alone. An absolutely amazing contributor by the name of Frank Donckers contacted me with the initial prototype of the translation engine, and it is Frank who is supplying the French, German, and Dutch translation text. I could not have built this feature without him – so thank you, Frank!

At present, the translation engine is pretty much complete in terms of base functionality – all program text is translated on the fly, and the user is free to change languages at run-time at their leisure (no restart required!). The coding solution behind this is quite elegant, if I might say so, and users shouldn’t experience any noticeable performance hit while a translation is active. The only noticeable delay might be an additional second or two of start-up time on older machines, on account of the translation XML file being loaded and parsed. I’ve got some ideas for speeding up this process, however, so even that delay may disappear by release time.

I would love to include official support for additional languages. If you are fluent in a language other than English, please consider contributing a new translation!

No programming experience or specialized software is required to translate. I’ve got a master translation file ready to go – all that’s needed is to plug in the translated text in whatever language you might speak.

Here is how the French language file looks.  All a translator needs to do is place a translation between the translation XML tags - easy peasy!
Here is how the French language file looks in the free Notepad++ editor. All a translator needs to do is place a translation between the translation XML tags – easy peasy!

If you’re familiar with XML or HTML, you can see how simple the translation document is. Each phrase consists of original text and translated text, and that’s all there is to it. The lines in green are just comments added for convenience, in this case comments written by the language extraction tool. Translators can safely ignore these.

Before wrapping up, I should mention one rather large caveat with multiple language support – at present, only “ANSI” (Windows-1252) languages are supported. I apologize for this, but one of the problems with classic VB is its inability to handle unicode characters without major hacking – and by major hacking, I mean replacing every user interface aspect of the project, as well as every string library. If I ever port PhotoDemon to another programming language (something I often consider), Unicode support would be much more feasible, but I’m afraid it’s not on the present roadmap.

I need at least a couple more weeks to hammer out a few remaining issues with version 5.4, which leaves plenty of time for any ambitious translators out there to pitch in and contribute a new translation before release day. If it helps, note that your name will be visibly displayed as the translator in not only the language source file, but I’ll also add you to the special thanks section of the program, the PhotoDemon website, and the README file.

I can always be reached via this contact form – so that’s the place to go if you’re willing to help. Thank you in advance!

Hooking modern Windows common dialogs: some notes

Background: common dialog hooking is used to append your own controls to a Windows common dialog box.

A good friend recently sent me a number of resources related to hooking common dialog controls. I’ve been interested in common dialog hooking for PhotoDemon, as it would allow me to add support for image previewing right in the dialog itself. This isn’t as necessary in modern versions of Windows (7 in particular includes a number of GDI+ improvements, making Explorer very robust with standard formats), but it can be helpful for unsupported formats like RAW photographs.

Unfortunately, several days of research have shown that it is not possible to hook a Vista or Windows 7 style dialog and maintain the modern layout. Let me explain with pictures:

This is the standard common dialog control in Windows Vista and 7 (and presumably 8 as well, though I haven't verified this myself).  The biggest improvements over past common dialogs include breadcrumb navigation at the top, a dedicated refresh button, and a persistent search bar.
This is the standard common dialog control in Windows Vista and 7 (and presumably 8 as well, though I haven’t verified this myself). The biggest improvements over past common dialogs include a dedicated left-hand file tree, breadcrumb navigation at the top, and a persistent search bar.

The common dialog above comes directly from PhotoDemon’s current common dialog implementation. This is the native common dialog control on Vista and 7. I very much like it. As a comparison, here is the same dialog in Windows XP:

Same folder as the previous image.  The XP common dialog provides no breadcrumb nav, folder tree, dedicated refresh, or search bar.  Note also how many TIFF formats do not display correctly - including XP not recognizing the MINISWHITE flag on the CCITT TIFF files.  Kinda interesting.
Same folder and images as the previous image. There is no breadcrumb nav, dedicated refresh, or search bar. Note also how many TIFF formats do not display correctly – including XP not recognizing the MINISWHITE flag on the CCITT TIFF files. Kinda interesting.

I strongly prefer the Vista/7-style dialog, particularly the breadcrumb nav and the persistent folder tree on the left.

Unfortunately, it is impossible to hook the Vista/7 dialog and maintain the native Vista/7 appearance. If you attempt to hook it, Windows will ALWAYS drop back to a previous generation common dialog. Here are some images to demonstrate, using a basic image preview hook:

This is what happens when you attempt to hook a dialog, and all you provide is the OFN_ENABLEHOOK flag.  Not pretty (and the hook doesn't even work right).
This is what happens when you attempt to hook a dialog, and all you provide is the OFN_ENABLEHOOK flag. Not pretty (and the hook doesn’t even work correctly).
Here is the same dialog, but with the OFN_EXPLORER flag set.  Note that hooking now works properly, but the common dialog itself has been reduced to XP style - the left-hand folder tree is gone, and the top bar has no breadcrumbs or search.
Here is the same dialog, but with the OFN_EXPLORER flag set. Note that hooking now works properly, but the common dialog itself has been reduced to XP style – the left-hand folder tree is gone, and the top bar has no breadcrumbs or search.

Note that the image above uses an older version of the OPENFILENAME struct, namely (this is its declaration in VB):

Private Type OPENFILENAME
    lStructSize       As Long
    hwndOwner         As Long
    hInstance         As Long
    lpstrFilter       As String
    lpstrCustomFilter As String
    nMaxCustFilter    As Long
    nFilterIndex      As Long
    lpstrFile         As String
    nMaxFile          As Long
    lpstrFileTitle    As String
    nMaxFileTitle     As Long
    lpstrInitialDir   As String
    lpstrTitle        As String
    Flags             As Long
    nFileOffset       As Integer
    nFileExtension    As Integer
    lpstrDefExt       As String
    lCustData         As Long
    lpfnHook          As Long
    lpTemplateName    As String
End Type

If you modify the struct to its newest version (as described here), you can slightly improve the dialog to look like this:

The newest version of the OPENFILENAME struct enables the places bar on the left.  I don't find this particularly useful - certainly not as useful as a folder pane - but perhaps some might find it preferable.
The newest version of the OPENFILENAME struct enables the places bar on the left. I don’t find this particularly useful – certainly not as useful as a folder pane – but perhaps some might find it preferable.

That is the best you can get if you want to hook a common dialog in Vista or 7.

Reasons for this have been speculated on by more qualified individuals than I. Over at stackoverflow, David H explains:

The reason for this is that MS completely re-organised the file dialogs for Vista. Hooks are used to extend a file dialog by supplying a resource file. This gives the customiser too much power. They can all too easily modify standard elements of the dialog and indeed many apps did so. The reorganisation of the dialogs would have broken many apps that used hooks. Those would have tried to manipulate elements of the dialog that were not there, or were implemented differently. Legacy versions of the dialogs remain for such apps to “get their hooks into”.

You are correct that it is impossible to get the new look when you use a hook. Instead you need to use the IFileDialogCustomize interface to customise the dialog. This is less powerful but does result in appearance and behaviour that is more consistent with the standard part of the dialog.

(More information is available here for those who are interested.)

Unfortunately, I am not aware of any way to access the iFileDialogCustomize interface in classic VB. If someone knows how, I’d love to hear it.

The take home message of all this is – if you work in classic VB and you want to hook a common dialog, you need to be content with an XP-style dialog. There is currently no way to maintain a Vista/7 style dialog while hooking.

For this reason, I’m going to stick with the stock common dialog control in PhotoDemon. I may look at a dedicated “browse” window in the future, which would allow for full image previewing, but I’m afraid such a feature is not on the roadmap for the next few versions.

All hooking-related screenshots were created using Carles PV’s iBMP project, which made it very easy to modify various hooking parameters and test the output. Thanks, Carles!

Image Dithering: Eleven Algorithms and Source Code

Dithering: An Overview

Today’s graphics programming topic – dithering – is one I receive a lot of emails about, which some may find surprising. You might think that dithering is something programmers shouldn’t have to deal with in 2012. Doesn’t dithering belong in the annals of technology history, a relic of times when “16 million color displays” were something programmers and users could only dream of? In an age when cheap mobile phones operate in full 32bpp glory, why am I writing an article about dithering?

Actually, dithering is still a surprisingly applicable technique, not just for practical reasons (such as preparing a full-color image for output on a non-color printer), but for artistic reasons as well. Dithering also has applications in web design, where it is a useful technique for reducing images with high color counts to lower color counts, reducing file size (and bandwidth) without harming quality. It also has uses when reducing 48 or 64bpp RAW-format digital photos to 24bpp RGB for editing.

And these are just image dithering uses – dithering still has extremely crucial roles to play in audio, but I’m afraid I won’t be discussing audio dithering here. Just image dithering.

In this article, I’m going to focus on three things:

  • a basic discussion of how image dithering works
  • eleven specific two-dimensional dithering formulas, including famous ones like “Floyd-Steinberg”
  • how to write a general-purpose dithering engine

Update 11 June 2016: some of the sample images in this article have been updated to better reflect the various dithering algorithms. Thank you to commenters who noted problems with the previous images!

Dithering: Some Examples

Consider the following full-color image, a wallpaper of the famous “companion cube” from Portal:

This will be our demonstration image for this article.  I chose it because it has a nice mixture of soft gradients and hard edges.
This will be our demonstration image for this article. I chose it because it has a nice mixture of soft gradients and hard edges.

On a modern LCD or LED screen – be it your computer monitor, smartphone, or TV – this full-color image can be displayed without any problems. But consider an older PC, one that only supports a limited palette. If we attempt to display the image on such a PC, it might look something like this:

This is the same image as above, but restricted to a websafe palette.
This is the same image as above, but restricted to a websafe palette.

Pretty nasty, isn’t it? Consider an even more dramatic example, where we want to print the cube image on a black-and-white printer. Then we’re left with something like this:

At this point, the image is barely recognizable.
At this point, the image is barely recognizable.

Problems arise any time an image is displayed on a device that supports less colors than the image contains. Subtle gradients in the original image may be replaced with blobs of uniform color, and depending on the restrictions of the device, the original image may become unrecognizable.

Dithering is an attempt to solve this problem. Dithering works by approximating unavailable colors with available colors, by mixing and matching available colors in a way that mimicks unavailable ones. As an example, here is the cube image once again reduced to the colors of a theoretical old PC – only this time, dithering has been applied:

A big improvement over the non-dithered version!
A big improvement over the non-dithered version!

If you look closely, you can see that this image uses the same colors as its non-dithered counterpart – but those few colors are arranged in a way that makes it seem like many more colors are present.

As another example, here is a black-and-white version of the image with similar dithering applied:

The specific algorithm used on this image is "2-row Sierra" dithering.
The specific algorithm used on this image is “2-row Sierra” dithering.

Despite only black and white being used, we can still make out the shape of the cube, right down to the hearts on either side. Dithering is an extremely powerful technique, and it can be used in ANY situation where data has to be represented at a lower resolution than it was originally created for. This article will focus specifically on images, but the same techniques can be applied to any 2-dimensional data (or 1-dimensional data, which is even simpler!).

The Basic Concept Behind Dithering

Boiled down to its simplest form, dithering is fundamentally about error diffusion.

Error diffusion works as follows: let’s pretend to reduce a grayscale photograph to black and white, so we can print it on a printer that only supports pure black (ink) or pure white (no ink). The first pixel in the image is dark gray, with a value of 96 on a scale from 0 to 255, with zero being pure black and 255 being pure white.

Here is an example of the RGB values in the example.
Here is a visualization of the RGB values in our example.

When converting such a pixel to black or white, we use a simple formula – is the color value closer to 0 (black) or 255 (white)? 96 is closer to 0 than to 255, so we make the pixel black.

At this point, a standard approach would simply move to the next pixel and perform the same comparison. But a problem arises if we have a bunch of “96 gray” pixels – they all get turned to black, and we’re left with a huge chunk of empty black pixels, which doesn’t represent the original gray color very well at all.

Error diffusion takes a smarter approach to the problem. As you might have inferred, error diffusion works by “diffusing” – or spreading – the error of each calculation to neighboring pixels. If it finds a pixel of 96 gray, it too determines that 96 is closer to 0 than to 255 – and so it makes the pixel black. But then the algorithm makes note of the “error” in its conversion – specifically, that the gray pixel we have forced to black was actually 96 steps away from black.

When it moves to the next pixel, the error diffusion algorithm adds the error of the previous pixel to the current pixel. If the next pixel is also 96 gray, instead of simply forcing that to black as well, the algorithm adds the error of 96 from the previous pixel. This results in a value of 192, which is actually closer to 255 – and thus closer to white! So it makes this particular pixel white, and it again makes note of the error – in this case, the error is -63, because 192 is 63 less than 255, which is the value this pixel was forced to.

As the algorithm proceeds, the “diffused error” results in an alternating pattern of black and white pixels, which does a pretty good job of mimicking the “96 gray” of the section – much better just forcing the color to black over and over again. Typically, when we finish processing a line of the image, we discard the error value we’ve been tracking and start over again at an error of “0” with the next line of the image.

Here is an example of the cube image from above with this exact algorithm applied – specifically, each pixel is converted to black or white, the error of the conversion is noted, and it is passed to the next pixel on the right:

This is the simplest possible application of error diffusion dithering.
This is the simplest possible application of error diffusion dithering.

Unfortunately, error diffusion dithering has problems of its own. For better or worse, dithering always leads to a spotted or stippled appearance. This is an inevitable side-effect of working with a small number of available colors – those colors are going to be repeated over and over again, because there are only so many of them.

In the simple error diffusion example above, another problem is evident – if you have a block of very similar colors, and you only push the error to the right, all the “dots” end up in the same place! This leads to funny lines of dots, which is nearly as distracting as the original, non-dithered version.

The problem is that we’re only using a one-dimensional error diffusion. By only pushing the error in one direction (right), we don’t distribute it very well. Since an image has two dimensions – horizontal and vertical – why not push the error in multiple directions? This will spread it out more evenly, which in turn will avoid the funny “lines of speckles” seen in the error diffusion example above.

Two-Dimensional Error Diffusion Dithering

There are many ways to diffuse an error in two dimensions. For example, we can spread the error to one or more pixels on the right, one or more pixels on the left, one or more pixels up, and one or more pixels down.

For simplicity of computation, all standard dithering formulas push the error forward, never backward. If you loop through an image one pixel at a time, starting at the top-left and moving right, you never want to push errors backward (e.g. left and/or up). The reason for this is obvious – if you push the error backward, you have to revisit pixels you’ve already processed, which leads to more errors being pushed backward, and you end up with an infinite cycle of error diffusion.

So for standard loop behavior (starting at the top-left of the image and moving right), we only want to push pixels right and down.

Apologies for the crappy image - but I hope it helps illustrate the gist of proper error diffusion.
Apologies for the crappy image – but I hope it helps illustrate the gist of proper error diffusion.

As for how specifically to propagate the error, a great number of individuals smarter than I have tackled this problem head-on. Let me share their formulas with you.

(Note: these dithering formulas are available multiple places online, but the best, most comprehensive reference I have found is this one.)

Floyd-Steinberg Dithering

The first – and arguably most famous – 2D error diffusion formula was published by Robert Floyd and Louis Steinberg in 1976. It diffuses errors in the following pattern:


       X   7
   3   5   1

     (1/16)

In the notation above, “X” refers to the current pixel. The fraction at the bottom represents the divisor for the error. Said another way, the Floyd-Steinberg formula could be written as:


           X    7/16
   3/16  5/16   1/16

But that notation is long and messy, so I’ll stick with the original.

To use our original example of converting a pixel of value “96” to 0 (black) or 255 (white), if we force the pixel to black, the resulting error is 96. We then propagate that error to the surrounding pixels by dividing 96 by 16 ( = 6), then multiplying it by the appropriate values, e.g.:


           X     +42
   +18    +30    +6

By spreading the error to multiple pixels, each with a different value, we minimize any distracting bands of speckles like the original error diffusion example. Here is the cube image with Floyd-Steinberg dithering applied:

Floyd-Steinberg dithering
Floyd-Steinberg dithering

Not bad, eh?

Floyd-Steinberg dithering is easily the most well-known error diffusion algorithm. It provides reasonably good quality, while only requiring a single forward array (a one-dimensional array the width of the image, which stores the error values pushed to the next row). Additionally, because its divisor is 16, bit-shifting can be used in place of division – making it quite fast, even on old hardware.

As for the 1/3/5/7 values used to distribute the error – those were chosen specifically because they create an even checkerboard pattern for perfectly gray images. Clever!

One warning regarding “Floyd-Steinberg” dithering – some software may use other, simpler dithering formulas and call them “Floyd-Steinberg”, hoping people won’t know the difference. This excellent dithering article describes one such “False Floyd-Steinberg” algorithm:


   X   3
   3   2

   (1/8)

This simplification of the original Floyd-Steinberg algorithm not only produces markedly worse output – but it does so without any conceivable advantage in terms of speed (or memory, as a forward-array to store error values for the next line is still required).

But if you’re curious, here’s the cube image after a “False Floyd-Steinberg” application:

Much more speckling than the legit Floyd-Steinberg algorithm - so don't use this formula!
Much more speckling than the legit Floyd-Steinberg algorithm – so don’t use this formula!

Jarvis, Judice, and Ninke Dithering

In the same year that Floyd and Steinberg published their famous dithering algorithm, a lesser-known – but much more powerful – algorithm was also published. The Jarvis, Judice, and Ninke filter is significantly more complex than Floyd-Steinberg:


             X   7   5 
     3   5   7   5   3
     1   3   5   3   1

           (1/48)

With this algorithm, the error is distributed to three times as many pixels as in Floyd-Steinberg, leading to much smoother – and more subtle – output. Unfortunately, the divisor of 48 is not a power of two, so bit-shifting can no longer be used – but only values of 1/48, 3/48, 5/48, and 7/48 are used, so these values can each be calculated but once, then propagated multiple times for a small speed gain.

Another downside of the JJN filter is that it pushes the error down not just one row, but two rows. This means we have to keep two forward arrays – one for the next row, and another for the row after that. This was a problem at the time the algorithm was first published, but on modern PCs or smartphones this extra requirement makes no difference. Frankly, you may be better off using a single error array the size of the image, rather than erasing the two single-row arrays over and over again.

Jarvis, Judice, Ninke dithering
Jarvis, Judice, Ninke dithering

Stucki Dithering

Five years after Jarvis, Judice, and Ninke published their dithering formula, Peter Stucki published an adjusted version of it, with slight changes made to improve processing time:


             X   8   4 
     2   4   8   4   2
     1   2   4   2   1

           (1/42)

The divisor of 42 is still not a power of two, but all the error propagation values are – so once the error is divided by 42, bit-shifting can be used to derive the specific values to propagate.

For most images, there will be minimal difference between the output of Stucki and JJN algorithms, so Stucki is often used because of its slight speed increase.

Stucki dithering
Stucki dithering

Atkinson Dithering

During the mid-1980’s, dithering became increasingly popular as computer hardware advanced to support more powerful video drivers and displays. One of the best dithering algorithms from this era was developed by Bill Atkinson, a Apple employee who worked on everything from MacPaint (which he wrote from scratch for the original Macintosh) to HyperCard and QuickDraw.

Atkinson’s formula is a bit different from others in this list, because it only propagates a fraction of the error instead of the full amount. This technique is sometimes offered by modern graphics applications as a “reduced color bleed” option. By only propagating part of the error, speckling is reduced, but contiguous dark or bright sections of an image may become washed out.


         X   1   1 
     1   1   1
         1

       (1/8)

Atkinson dithering
Atkinson dithering

Burkes Dithering

Seven years after Stucki published his improvement to Jarvis, Judice, Ninke dithering, Daniel Burkes suggested a further improvement:


             X   8   4 
     2   4   8   4   2

           (1/32)

Burkes’s suggestion was to drop the bottom row of Stucki’s matrix. Not only did this remove the need for two forward arrays, but it also resulted in a divisor that was once again a multiple of 2. This change meant that all math involved in the error calculation could be accomplished by simple bit-shifting, with only a minor hit to quality.

Burkes dithering
Burkes dithering

Sierra Dithering

The final three dithering algorithms come from Frankie Sierra, who published the following matrices in 1989 and 1990:


             X   5   3
     2   4   5   4   2
         2   3   2
           (1/32)


             X   4   3
     1   2   3   2   1
           (1/16)


         X   2
     1   1
       (1/4)

These three filters are commonly referred to as “Sierra”, “Two-Row Sierra”, and “Sierra Lite”. Their output on the sample cube image is as follows:

Sierra (sometimes called Sierra-3)
Sierra (sometimes called Sierra-3)
Two-row Sierra
Two-row Sierra
Sierra Lite
Sierra Lite

Other dithering considerations

If you compare the images above to the dithering results of another program, you may find slight differences. This is to be expected. There are a surprising number of variables that can affect the precise output of a dithering algorithm, including:

  • Integer or floating point tracking of errors. Integer-only methods lose some resolution due to quantization errors.
  • Color bleed reduction. Some software reduces the error by a set value – maybe 50% or 75% – to reduce the amount of “bleed” to neighboring pixels.
  • The threshold cut-off for black or white. 127 or 128 are common, but on some images it may be helpful to use other values.
  • For color images, how luminance is calculated can make a big difference. I use the HSL luminance formula ( [max(R,G,B) + min(R,G,B)] / 2). Others use ([r+g+b] / 3) or one of the ITU formulas. YUV or CIELAB will offer even better results.
  • Gamma correction or other pre-processing modifications. It is often beneficial to normalize an image before converting it to black and white, and whichever technique you use for this will obviously affect the output.
  • Loop direction. I’ve discussed a standard “left-to-right, top-to-bottom” approach, but some clever dithering algorithms will follow a serpentine path, where left-to-right directionality is reversed each line. This can reduce spots of uniform speckling and give a more varied appearance, but it’s more complicated to implement.

For the demonstration images in this article, I have not performed any pre-processing to the original image. All color matching is done in the RGB space with a cut-off of 127 (values <= 127 are set to 0). Loop direction is standard left-to-right, top-to-bottom.

Which specific techniques you may want to use will vary according to your programming language, processing constraints, and desired output.

I count 9 algorithms, but you promised 11! Where are the other two?

So far I’ve focused purely on error-diffusion dithering, because it offers better results than static, non-diffusion dithering.

But for sake of completeness, here are demonstrations of two standard “ordered dither” techniques. Ordered dithering leads to far more speckling (and worse results) than error-diffusion dithering, but they require no forward arrays and are very fast to apply. For more information on ordered dithering, check out the relevant Wikipedia article.

Ordered dither using a 4x4 Bayer matrix
Ordered dither using a 4×4 Bayer matrix
Ordered dither using an 8x8 Bayer matrix
Ordered dither using an 8×8 Bayer matrix

With these, the article has now covered a total of 11 different dithering algorithms.

Writing your own general-purpose dithering algorithm

Earlier this year, I wrote a fully functional, general-purpose dithering engine for PhotoDemon (an open-source photo editor). Rather than post the entirety of the code here, let me refer you to the relevant page on GitHub. The black and white conversion engine starts at line 350. If you have any questions about the code – which covers all the algorithms described on this page – please let me know and I’ll post additional explanations.

That engine works by allowing you to specify any dithering matrix in advance, just like the ones on this page. Then you hand that matrix over to the dithering engine and it takes care of the rest.

The engine is designed around monochrome conversion, but it could easily be modified to work on color palettes as well. The biggest difference with a color palette is that you must track separate errors for red, green, and blue, rather than a single luminance error. Otherwise, all the math is identical.

 

This site - and its many free downloads - are 100% funded by donations. Please consider a small contribution to fund server costs and to help me support my family. Even $1.00 helps. Thank you!

Announcing PhotoDemon 5.2 – Selections, HSL, Rotation, HDR, and More

Summary

PhotoDemon v5.2 is now available. New features include selection tools, arbitrary rotation, HSL adjustments, CMYK support, new user preferences, multiple monitor support, and more. Download the update here.

PhotoDemon 5.2
Version 5.2 includes many new tools and features, including PhotoDemon’s first on-canvas tool – “Selections”.

New Feature: Selection Tool

Selections have been one of the top-requested PhotoDemon features since it first released, so I’m glad to finally be able to offer them. A lot of work went into making selections as user-friendly and powerful as possible.

Three render modes are provided. On-canvas resizing and moving are fully supported, as are adjustments by textbox (see screenshot above). Everything in the Color and Filter menus will operate on a selection if available, as well as the Edit -> Copy command.

(Note: as of this v5.2, selections are not yet tied into Undo/Redo, and selections will not be recorded as part of a Macro. These features will be added in the next release.)

New Feature: Crop to Selection

Finally!

New Feature: HSL Adjustments

PhotoShop and GIMP users should be happy about this tool.

New Feature: Arbitrary (Free) Rotation

Arbitrary rotation comes courtesy of the FreeImage library. A 3-shear method is used: very fast, very high quality.

New Feature: CMY/K Rechanneling

Both CMY and CMYK rechanneling are now available.

New Feature: Sepia (W3C formula)

Here’s the sepia version of the photo from the Rechannel screenshot. I still prefer PhotoDemon’s “Antique” filter for most photos, but this sepia formula (from the W3C spec) provides a pleasant, flat alternative.

New Feature: Preferences Dialog (rewritten from scratch)

Preferences, preferences, and more preferences. The old Preferences dialog was pretty lame, so it was due for an overhaul. Tons of new settings have been added, and they are now organized by category.

New preferences include:

Interface:

  • Render drop shadows between images and canvas (similar to Paint.NET)
  • Full or compact file paths for image windows and Recent File shortcuts
  • Improved font rendering on Vista, Windows 7, and Windows 8 (via Segoe UI)
  • Remember the main window’s location between sessions

Loading and Saving:

  • Tone map imported HDR and RAW images
  • Options for importing all frames or pages of multi-image files (animated GIFs, multipage TIFFs)

Tools:

  • Automatically clear selections after “Crop to Selection” is used

Transparency handling:

  • Pick your own transparency checkerboard colors
  • Pick from three transparency checkerboard sizes (4×4, 8×8, 16×16)
  • Allow PhotoDemon to automatically remove empty alpha channels from imported images

All preferences from v5.0 remain present, and there is now an option to reset all preferences to their default state – so experiment away!

New Feature: Recent File Previews (Vista, Windows 7, Windows 8 only)

Now that recent file previews are available, I honestly can’t use any software that *doesn’t* provide the feature. It makes locating the right file significantly easier – especially with digital camera filenames like IMG_0366.jpg.

New Feature: Multi-Image File Support (animated GIFs, multipage TIFFs)

PhotoDemon will now recognize when you try to load image files that are actually composed of multiple images. You are given the option to import every image, or just the first one (which is what most other software does). The default behavior can be changed in the Edit -> Preferences menu.

New Feature: Waaaay better transparency handling, including adding/removing alpha channels

It’s hard to overstate how much better transparency support is in v5.2 compared to v5.0. Images with alpha-channels are now rendered as alpha in all viewport, filter, and tool screens. When printing, saving as 24bpp, or copying to the clipboard, transparent images are automatically composited against a white background. As mentioned previously, user preferences have been added for transparency checkerboard color and sizes.

PhotoDemon also allows you to add or remove alpha channels entirely. Here’s an example of an image with an alpha channel, and the associated “Image Mode” setting:

Note how the top-level “Mode” icon has changed to match the current mode – this saves you from having to go to the sub-menu to check. I’m a big fan of small touches like this.

And here it is again, after clicking the “Mode -> Photo (RGB | 24bpp | no transparency)” option:

No more alpha!

Finally, PhotoDemon now validates all incoming alpha channels. If an image has a blank or irrelevant alpha channel, PhotoDemon will automatically remove it for you. This frees up RAM, improves performance, and leads to a much smaller file size upon saving. (Note: this feature can be disabled from the Edit -> Preferences menu if you want to maintain blank alpha channels for some reason.)

New Feature: Custom “Confirm Unsaved Image(s)” Prompt

This is the new “unsaved images” prompt in PhotoDemon. A preview is now provided – again, very important for digital photos with obscure names – and the options have been reworked to make them as crystal-clear as possible. Also handy is the “Repeat this action for all unsaved images” option, which will either save or not save all unsaved images per your request.

Improved Feature: Edge Detection

Edge detection now allows for on-black or on-white processing. Generally speaking, on-white is used for artistic purposes, while on-black is used for technical and research ones. (Thanks to Yvonne Strahovski, who appears in the sample image above.)

New Feature: Thermograph Filter

This Wikipedia article describes thermography in great detail. PhotoDemon’s thermography filter works by correlating luminance with heat, and analyzing the image accordingly. Here’s a sample, using a picture of the lovely Alison Brie, of Mad Men and Community fame:

New Feature: JPEG 2000 (JP2/J2K), Industrial Light and Magic (EXR), High-Dynamic Range (HDR) and Digital Fax (G3) image support

PhotoDemon now supports importing the four image types mentioned above, and it also supports JPEG 2000 exporting.

Other New and Improved Features:

  • Much faster resize operations, thanks to an updated FreeImage library (v3.15.4)
  • Multiple monitor support during screen captures (File -> Import -> Screen Capture)
  • Many miscellaneous interface improvements, including generally larger command buttons, text boxes, labels, and more uniform form layouts.
  • Many new and improved menu icons.
  • Heavily optimized viewport rendering. PhotoDemon now uses a triple-buffer rendering pipeline to speed up actions like zooming, scrolling, and using on-canvas tools like the new Selection Tool. Even when working with 32bpp images, all actions render in real-time.
  • Bilinear interpolation is now used during Isometric Conversion. This results in a much higher-quality transform. Hard edges are still left along the image border to make mask generation easy for game designers.
  • Vastly improved image previewing when importing from VB binary files.
  • Better text validation throughout the software. Invalid values are now handled much more elegantly.
  • More accelerator hotkey support, including changes to match Windows standards (such as Ctrl+Y for Redo, instead of the previous Ctrl+Alt+Z).
  • Update checks are now performed every ten days (instead of every time the program is run).
  • All extra program data – including plugins, preferences, saved filters and macros – have been moved to a single /Data subfolder. If you run PhotoDemon on your desktop, this should make things much cleaner for you.
  • PhotoDemon’s current and max memory usage is now displayed in the Preferences -> Advanced panel.
  • Tons of miscellaneous bug fixes, tweaks, and optimizations. For a full list of changes, visit https://github.com/tannerhelland/PhotoDemon/commits/master

In Conclusion…

Not bad for two months work, eh? I hope you enjoy all the new features in 5.2., and please remember to donate if you find the software useful!

Announcing PhotoDemon 5.2 Beta 1 – Testers Needed!

PhotoDemon 5.2 beta 1 screenshot
It’s time for another PhotoDemon update. This update includes many new tools, including PhotoDemon’s first on-canvas tool – “Selections”.
  1. Summary
  2. Download
  3. List of what’s new and improved

Summary

PhotoDemon 5.2 is nearing completion, and I need help testing it. Version 5.2 provides a bunch of new features, including selections, cropping, HSL adjustment, CMY/CMYK rechanneling, a new Sepia filter (based off the W3C standard), an overhauled preferences engine and interface, and more. Please download the beta and help me make sure everything is working properly.

Download

The PhotoDemon 5.2 beta comes in two flavors:

Remember – if you are an advanced user, you can always download the most recent development build of PhotoDemon’s source code from its GitHub page.

PhotoDemon is funded by donations from users like you.
Please consider a small donation to fund development and to help me support my family.
Even $1.00 helps. Thank you!

List of what’s new and improved in v5.2 (so far)

  • Selection tool! It’s a hell of a tool, and a lot of work went into making it as user-friendly and powerful as possible. Three render modes are provided. On-canvas resizing and moving are fully supported as well. Everything in the Color and Filter menus will operate on a selection if available, as well as the Edit -> Copy command. (Note: as of this beta, selections are not yet tied into Undo/Redo, and selections will not be recorded as part of a Macro.)
  • PhotoDemon Selection Tool
    Here’s an example of the selection tool in action. Note that the HSL adjustment tool is only operating on the selected area.
  • Image cropping is now possible via the Crop-to-Selection option (in the Image menu).
  • New HSL adjustment tool. (See above screenshot for sample.)
  • New Rechannel tool. Live previews, CMY, and CMYK color spaces were added.
  • PhotoDemon’s new and improved Rechannel tool.
  • New Sepia filter based off the official W3C formula (available here). I still prefer PhotoDemon’s “Filters -> Antique” effect, but felt it was worthwhile to make both available.
  • Here’s the sepia version of the photo from the Rechannel screenshot. I took this photo during a hike up Spanish Fork Canyon several weeks ago; the fall colors were stunning.
  • Vast improvements to PhotoDemon’s support for images with transparency. Images with alpha-channels will now be rendered as alpha in all filter and tool screens. When printing, saving as 24bpp, or copying to the clipboard, the image will be composited against a white background. User preferences were also added for transparency checkerboard color and sizes.
  • All-new User Preferences dialog. Many new options were added, and the Preferences interface is now sorted by category.
  • Interface-related options in the new Preferences dialog.
    As another example, here are the afore-mentioned transparency handling options.
  • Improved font rendering is now available for users on Windows Vista, Windows 7, and Windows 8.
  • A drop-shadow can now be rendered between the image and the canvas (similar to Paint.NET).
  • PhotoDemon is now capable of remembering its window size and position between sessions.
  • Multiple monitors are now supported by the Import -> Screen Capture tool.
  • Many miscellaneous interface improvements. Additionally, I am testing a new layout in the Color -> Grayscale tool. This layout style is intended to help users make sense of PhotoDemon’s many options. Let me know what you think, because if this style is popular, I will redo the other tool dialogs to match.
  • Heavily optimized viewport rendering. PhotoDemon now uses a triple-buffer rendering pipeline to speed up actions like zooming, scrolling, and using on-canvas tools like the new Selection Tool. Even when working with 32bpp images, all actions should render in real-time on any modern system.
  • Bilinear interpolation is now used in “Convert to Isometric Image”. This results in a much higher-quality transform. Hard edges are still left along the image border to make mask generation easy for game designers.
  • Many bug fixes and miscellaneous improvements. For complete details, please visit the commit log at https://github.com/tannerhelland/PhotoDemon/commits/master

Announcing PhotoDemon 5.0 Beta 1 – Testers Needed!

  1. Summary
  2. Download
  3. PhotoDemon 5.0: A Bit of Background
  4. List of what’s new and improved
PhotoDemon’s biggest update in years is nearing completion, which means it’s time for you to try and break it. Give it a spin and let me know what you think of the improvements (which are many!)

Summary

PhotoDemon 5.0 is nearing completion, and I need help testing it. Version 5.0 includes an all-new image subsystem that required rewriting every filter and effect in the program (and some 17,000 lines of code!). All those changes have made the software significantly faster and smoother, but it might also have broken a few things. Download the beta and help me make sure everything is working the way it’s supposed to.

Download

The PhotoDemon 5.0 beta 1 comes in two flavors:

Remember – if you are an advanced user, you can always download the most recent development build of PhotoDemon’s source code from its GitHub page.

PhotoDemon is funded by donations from users like you.
Please consider a small donation to fund development and to help me support my family.
Even $1.00 helps. Thank you!

PhotoDemon 5.0: A Bit of Background

As you might know, PhotoDemon has a long and complicated history spanning some 12 years. That longevity has some perks – for example, tons of features – but it also has some downsides.

One of the biggest downsides to being 12 years old is that the software carries with it some bad design choices, made many years ago when I was a young and immature programmer, that have perpetually bogged down the implementation of new and exciting features. In particular, features like large images, selections, and alpha-channel (transparency) support have all been impossible because of the way PhotoDemon stores and renders images. Originally, the software was only meant to work on 8-bit images, and 24-bit support was later tacked on as an afterthought. I took that framework as far as I could go, but upon releasing PhotoDemon to the public earlier this year, I realized that it was time to fix that problem.

Enter version 5.0.

PhotoDemon 5.0 has just about been rewritten from the ground up, and I don’t say that lightly. The software is comprised of some 30,000 lines of code, and version 5.0 involved the writing of more than half (17,000) of those lines. Why? Because it was finally time for a completely new image subsystem, one capable of potentially supporting selections, alpha-channels, high bit-depths, layers, and whatever else I might want to someday throw at it.

(Note: features like selections are not yet part of PhotoDemon. They will take a good chunk of time to write – but at least now it will be physically possible to add them!)

This new image subsystem is something I’m very proud of. At a high level, it’s basically a specialized image class that stores and tracks all image data, and passes that data between the screen, image files, and various filters and effects. The subsystem does not rely on anything specific to Visual Basic (the programming language PhotoDemon is written in), meaning it is capable of supporting any features it wants – regardless of whether or not VB actually supports them. Past versions of PhotoDemon relied on VB’s inherent “picture boxes”, as they are called, for image storage and processing, and because VB6 is now 14 years old it simply couldn’t handle things like large images or transparency.

But no more.

This rewrite has been a massive project, and every single filter and tool (every damn one!) had to be rewritten to accommodate the new technology. This proved to be a good thing, because I hadn’t revisited some of those filters for over a decade, and in the past ten years I’ve learned a great deal about writing cleaner, better, faster imaging code. That made this a prime chance to re-engineer every filter and tool in the program to make it as fast and accurate as possible, and I think you’ll like the result.

But enough about this – you probably want to know what’s actually new in PhotoDemon 5.0. I won’t discuss everything here (some features are still under construction), but here are the highlights.

List of what’s new and improved in v5.0 beta 1

  • Everything is faster – all filters, tools, effects, loading images, saving images, macros, batch conversion, undo/redo. Seriously – EVERYTHING.
  • Completely rewritten image load/save code. As an example of how much better the new version is: I ran two identical batch conversions of 138 wedding photos (10 megapixels each, 3872×2592 pixels). The batch conversion was simple – load each image, then save it in another folder at a different JPEG quality. PhotoDemon 4.4 did the conversion in 2 minutes 21 seconds. The PhotoDemon 5.0 beta did it in 1 minute 11 seconds. (Thanks to Herman Liu for much testing and help with the implementation!)
  • Redesigned menus. Every item has a descriptive icon, and menus have been reorganized according to improved design rules
  • Menus now have useful icons and improved organization
  • Drag-and-Drop compatibility. Drag images from your desktop or file manager onto PhotoDemon, and it will open them all automatically. (Thanks to Kroc of camendesign.com for the suggestion!)
  • MUCH better Wine compatibility for OSX and Linux users. Undo/Redo and all tools and effects should now work under Wine. Let me know if you find any that do not.
  • New “Tile” tool tiles the current image to a target size (in pixels) or number of tiles. (Thanks to Ye Peng for the suggestion!)
  • PhotoDemon’s new “Tile” tool
  • New “Duplicate Image” tool. Perfect for making a working copy of an image without fear of overwriting the original. (Thanks to Achmad Junus for the suggestion!)
  • Auto-Enhance overhaul. All four auto-enhance tools (contrast, highlights, midtones, shadows) have been rewritten from scratch using completely new algorithms. I think you’ll find them way more useful than the old tools.
  • Improved mosaic tool. Faster, higher quality, and mosaics can now be as large as the image or as tiny as one pixel in either dimension.
  • Added previewing to a bunch of forms that lacked it before – Reduce Colors (Quantize), Black and White Conversion, Find Edges
  • Increased size of all preview windows. They are now much larger, which makes it easier to see how a filter or tool will affect an image.
  • Improved handling of edge pixels for all convolution filters (blur, soften, sharpen, etc)
  • Improved color reduction algorithms (faster and higher quality)
  • Floating-point implementation of histogram equalization means it is now significantly more accurate
  • DPI-aware images mean no more distortion at 120dpi – a big improvement for people using “larger font” settings in Windows
  • No limit on image sizes. The bigger, the better. (Thanks to Robert Rayment for his help with this bug!)
  • Full GDI+ support for saving and loading. If the FreeImage plugin can’t be found, GIF/JPEG/PNG/TIFF import and export will still be available. (Thanks to Alfred Hellmueller for the suggestion to add GDI+ compatibility!)
  • Turbo JPEG loading while batch conversions are running
  • Improved bug reporting system and online form to match
  • Tons of miscellaneous bug fixes, tweaks, and optimizations

Announcing PhotoDemon: A Fast, Free, Open-Source Photo Editor and Image Processor

PhotoDemon screenshot
PhotoDemon v4.2 in the midst of a massive batch conversion (1643 files)

tl;dr – I’ve spent 12 years working on an advanced image processing program. (Think PhotoShop, but without any on-canvas painting tools.) The software is now available under the title “PhotoDemon.” It is fast, free, completely open-source (BSD licensed), and it provides a number of useful features, including macro recording and automated batch conversion. You can download it here.

I can’t often say that a blog post has been 12 years in the making… but believe it or not, this post has taken me that long to write.

Many years ago, when I was but a lowly high school student, I legitimately believed that I alone could produce the world’s greatest video game. It was going to be epic in every possible way – immersive 3D graphics, fully orchestrated musical score, hundreds of pages of witty dialogue. I was going to program the whole thing myself in Visual Basic 6.0, and it was going to be AWESOME.

(ROFL)

This might shock you, but that game never came to fruition.

Fortunately, my delusional teenage aspirations weren’t entirely a waste – I did end up writing many hours of original music for the game, and I also produced a suite of useful development tools. One of those tools was called the GenesisX Image Studio, after my one-man GenesisX Production Company. (Yes, that name sounded cool to my teenage mind.) The purpose of GenesisX Image Studio was to convert 24-bit image files to the game’s custom 8-bit Genesis X Format.

Perhaps you recall, but back in the year 2000 bandwidth was hard to come by, and distributing a game chock full of large 24-bit images over the Internet simply wasn’t feasible. GIF images were still under patent protection so there were concerns about using them, and PNG wasn’t widely known or supported. So I decided to write my own image format, and this was the program capable of converting JPEGs and BMPs to that:

GXF Compressor screenshot
Here’s a screenshot of the GenesisX Image Studio. I know – it burns the eyes a little. Don’t you love the red/black gradient? It seemed so edgy at the time. (facepalm)

While the GXF Compressor was hideous to look at, it included some interesting code, including a rather clever interactive palette editor. That palette editor was at the heart of the Genesis X Format. It worked by taking 256-color images and blending low-frequency colors at a ratio of their occurrences within the image. This way, it was possible to get a 256-color image down to 128 colors or less with very little degradation; the image would then be RLE compressed and optionally zLib compressed, and it was capable of producing downright tiny files.

GXF Palette Editor
The GenesisX Palette Editor. I’m not sure why I felt the need to plaster a bright red copyright message on the form… I’m fairly certain no one was interested in stealing my painfully amateurish code.

When the ultimate game project associated with this software died, I continued to peck away at the image studio, mostly because I enjoyed learning about image processing and the software already provided a framework for things like loading and saving images, zooming and scrolling them, and a rudimentary set of filters. Over time, I eliminated the 256-color feature set and focused only on 16 million color support. Eventually the ridiculous “GenesisX” moniker was dropped, and the project was renamed “DemonSpectre Image Workshop.” (DemonSpectre was my online alias at the time.)

DemonSpectre Image Workshop
By 2002, the project had become slightly less hideous. The red/black gradient was replaced by the blue/black gradient made famous by InstallShield, and a thoroughly useless logo was added to the left-hand side. The code base also grew to include a variety of new filters and processing techniques.

In 2002, Microsoft introduced the first version of Visual Studio .NET, effectively obsoleting the COM-based VB6 overnight. I was in university by then, and had become very aware that VB was not the right language for a programmer who wanted to be taken seriously in the U.S. job market. So I learned C++, java, and Perl, though I retained a love for classic VB, in large part because it was the language that got me into programming in the first place.

The next 8-9 years saw slow, incremental upgrades to the software, usually the result of a random night or weekend when I was fed up with work and needed to focus on something not-work-related. Eventually I renamed the software “VB Photoshop” (no copyright problems there!), then later PhotoDemon, a mash-up of my old DemonSpectre moniker and the fact that the software had grown to focus primarily on photo editing.

In fact, my interest in digital photography led to many of the program’s best features, since I used PhotoDemon to implement tools that other image editing programs lacked or implemented poorly. (I’m looking at you, PhotoShop batch conversion!) Since its inception, PhotoDemon also served as a testbed for my image processing work in other programming languages, because for all its flaws, classic VB is unbeatable as a rapid prototyping language. I still use it for first-implementation tests of obscure features or filters, simply because I can go from pseudocode to real-time implementation in minutes (versus hours in java, and days/months in C). And because VB6 compiles down to native code (unlike the interpreted P-code of earlier versions), it’s perfect for prototyping image processing code, which often needs to execute in real-time.

PhotoDemon v4.2 menu screenshot
PhotoDemon has come a long way from its original GenesisX Image Studio roots. The current version looks quite nice, and it includes features I find lacking in other software – such as extensive accelerator (“hotkey”) support. For those who don’t utilize accelerators, the menus are designed to maximize discoverability. IMO they’re a significant improvement over most image editing software menus.

Because I continued to receive a surprising amount of traffic to my VB-oriented programming site, I would periodically strip interesting features out of PhotoDemon and publish them independently. In fact, most of my open-source programming projects are merely subsets of PhotoDemon’s codebase. (And it’s a surprisingly large codebase – over 30,000 lines – and that’s not including the 3rd-party DLLs it relies on for extra functionality.)

Every now and then, I’ll receive an email from a poor programmer who’s stuck supporting a legacy VB6 application and has consequently stumbled across my site. These emails always brighten my day, and they’re the reason I still provide VB6 projects despite the language being “dead” for more than 10 years. (Although “dead” is a relative term – Microsoft’s extended support lasted until 2008, and they have promised “it just works” compatibility for VB6 applications FOR THE LIFETIME of Windows 8. I know people have their criticisms of Microsoft, but no major tech company is half as good as they are when it comes to supporting legacy software. Hats off to Microsoft for that.)

Occasionally, these emails will ask me if I have a single project that condenses my many image processing techniques into a single piece of software. For ten years, my response to this question has been a vague, teasing, “maybe I do – you’ll have to wait and see!” I’m not sure why I’ve never just tell people about PhotoDemon… probably because they would pester me for copies of the code, and I hate sending out .zip files of large source directories, especially when I haven’t made up my mind about how I want to license said code.

But this summer, as I was sending out yet another one of these vague email responses, it struck me that I’d spent the past ten years hinting at PhotoDemon but never really thinking seriously about when it might live somewhere besides my hard drive. Wasn’t it time to seriously commit to getting the project in a workable state? (Anyone who knows me shouldn’t find this surprising – my motto has always been “better late than never,” and boy does this project meet that definition!)

So I committed, then and there, to getting PhotoDemon into a workable state. My last three months have been spent cleaning up its code base, stripping out useless functions and features, writing documentation, and coaxing it to work with modern Windows visual styles – no small feat, considering VB6 never worked with Windows XP visual styles, let alone Windows 7.

PhotoDemon current version screen shot
PhotoDemon, as it looks in August 2012. Note the use of Windows 7 visual styles, along with full MDI support. Also – no hideous background gradient! :)

Because I’m a glutton for punishment, I also got PhotoDemon working with modern version control software. (Here it is on GitHub.) I wonder if I’m the first person to try and get a massive VB6 codebase working properly with Git… Surprisingly, it does work, though it takes some tweaking thanks to VB’s strange intermixing of text and binary files. Maybe someday I’ll document what I did. Then again, maybe not – I’m not sure I want people trying to set up legacy VB projects with GitHub, lol.

After getting the code to a pleasantly robust state, I put up a preliminary project page for PhotoDemon on this site. That was six weeks ago. Thus far it seems to have been well-received among the VB programmers who frequent my site, and with the help of those programmers, many miscellaneous bugs have been squashed. After a rigorous few weeks of testing, I think PhotoDemon is finally stable enough to warrant broader use.

And that’s why this blog post exists.

Over the next few weeks, possibly months, I plan on releasing a series of “developer diaries” that discuss PhotoDemon’s features and design in detail. I don’t know many projects with a 12-year development time that spans from the developer first learning to program to becoming a professional coder, and I think my experiences could be useful for other young programmers looking to embark on their own open source project. Also, some of PhotoDemon’s more advanced capabilities – such as macro recording and playback – represent unique design challenges, and I think it could be worthwhile to discuss the implementation hurdles I faced in hopes of helping other programmers build such features right on their first try.

PhotoDemon v4.2 print dialog
PhotoDemon’s current interface aims to find that sweet spot between minimalism and power. For example, here’s the print dialog. I find most print dialogs to be woefully over-engineered, so this one provides only the options I use on a regular basis. Also, I just noticed that the “Orientation” label is misaligned vertically. D’oh! Better go fix that…

But for now, here’s what’s worth mentioning: PhotoDemon is stable, and I’d love your feedback on it. It’s designed as a portable app, meaning no installer is required. Just download the .zip, extract it, and run PhotoDemon.exe. (Not a Windows user? PhotoDemon should work with the latest stable release of Wine.)

Input is welcome from programmers and non-programmers alike. To download just the executable, use this link:

Download PhotoDemon (software only, no source code)

If you want the program AND its complete source code, download it from PhotoDemon’s GitHub page:

Download PhotoDemon (with complete source code)

A GitHub account is not required. Simply click the “ZIP” button with the cloud-and-arrow icon to download the source in standard VB6 format. (The ZIP button is just below the project description, in the top-left quadrant of the page.)

Issues can be submitted from the “Help” menu within PhotoDemon, or by visiting the Issues page, or by simply sending me an email.

Stay tuned for posts describing PhotoDemon’s (quite large) feature set in detail, as well as in-depth guides for its advanced features, including macro recording and batch conversion.

Finally, note that PhotoDemon is updated regularly. I tend to make commits on at least a weekly basis, and often more frequently than that. For the most up-to-date version of the software, download it from GitHub.

Thanks for your interest, and I hope you enjoy the software.