KGy SOFT Drawing Libraries offer advanced bitmap data manipulation and image processing features such as quantizing and dithering. The libraries consist of multiple packages. A core library contains the technology-agnostic and platform independent functionality and there are specialized libraries built upon the core package.

1. Download
   • Available Packages
   • Application Examples
2. Project Site
3. Documentation
4. Release Notes
5. Examples
   • Icon Manipulation
   • Fast Bitmap Manipulation
   • Managed Bitmap Data Manipulation
   • WriteableBitmap and Other 3rd Party Bitmap Types Support
   • Supporting Custom Pixel Formats
   • Quantizing and Dithering
   • Advanced GIF Encoder with High Color Support
6. License

Starting with version 7.0.0 KGy SOFT Drawing Libraries are available in multiple packages:

⚠️ Note: Version 7.0.0 is currently in preview. As a stable release, you can only download the combined KGySoft.Drawing package so far. Version 7.0.0 intruduces several major breaking changes due to the assembly split. Feel free to refer to the release notes.

This package contains the platform-independent core functionality that mainly resides in the KGySoft.Drawing.Imaging namespace.

Main highlights:

• Creating managed bitmap data of any pixel format.
• Creating bitmap data for any preallocated buffer using any pixel format. This allows accessing the pixels of bitmaps of any technology if the bitmap data is exposed as a pointer or array.
• Quantizing using predefined or optimized colors
• Dithering using ordered, error diffusion, random noise or interleaved gradient noise dithering techniques
• Creating GIF animations even in high color

The package can be downloaded directly from NuGet or by using the Package Manager Console:

PM> Install-Package KGySoft.Drawing.Core

This package provides special support for System.Drawing types such as Bitmap, Metafile, Image, Icon, Graphics. In .NET 7 and above this package can be used on Windows only. When targeting earlier versions, Unix/Linux based systems are also supported (if the libgdiplus library is installed).

Main highlights:

• Fast direct native Bitmap data access for every PixelFormat
• Quantizing and dithering
• Creating GIF animations even in high color
• Several built-in icons as well as simple access to Windows associated and stock icons.
• Extracting bitmaps from multi-frame bitmaps and icons.
• Creating combined icons and multi-resolution bitmaps.
• Saving metafiles in EMF/WMF formats.
• Advanced support for saving images as Icon, BMP, JPEG, PNG, GIF and TIFF formats.
• Converting between various pixel formats preserving transparency if possible.
• Useful extensions for the Icon, Bitmap, Image, Metafile and Graphics types.

The package can be downloaded directly from NuGet or by using the Package Manager Console:

PM> Install-Package KGySoft.Drawing

This package helps accessing the bitmap data of the WriteableBitmap type in WPF supporting all of its possible pixel formats. It also allows direct read-only access to the bitmap data of any BitmapSource.

The package can be downloaded directly from NuGet or by using the Package Manager Console:

PM> Install-Package KGySoft.Drawing.Wpf

This package helps accessing the bitmap data of the WriteableBitmap type in UWP (Universal Windows Platform). This library requires targeting at least Windows 10.0.16299.0 (Fall Creators Update, version 1709) so it can reference the .NET Standard 2.0 version of the dependent core libraries.

The package can be downloaded directly from NuGet or by using the Package Manager Console:

PM> Install-Package KGySoft.Drawing.Uwp

This package helps accessing the bitmap data of the WriteableBitmap type of the Windows App SDK used in WinUI applications. This library requires targeting at least .NET 5 and Windows 10.0.17763.0 (October 2018 release, version 1809).

The package can be downloaded directly from NuGet or by using the Package Manager Console:

PM> Install-Package KGySoft.Drawing.WinUI

KGy SOFT Imaging Tools is a Windows Forms desktop application in the KGySoft.Drawing.Tools repository, which nicely demonstrates a sort of features of Drawing Libraries, such as quantizing and dithering, resizing, adjusting brightness, contrast and gamma, etc. The tool is packed also with some debugger visualizers for several System.Drawing types including Bitmap, Metafile, Icon, Graphics and more.

KGy SOFT Imaging Tools

ScreenToGif is a WPF desktop application that can be used to create and save animations. Among others, it can use KGy SOFT Drawing Libraries to save GIF animations using various quantizers and ditherers.

KGy SOFT GIF encoder options in ScreenToGif

Find the project site at kgysoft.net

The following links refer to the combined documentation of the available packages. Check the indicated Assembly at the help pages that also designates the corresponding package.

• Online documentation
• Offline .chm documentation

Starting with version 7.0.0 each packages have their own change logs:

• KGySoft.Drawing.Core change log
• KGySoft.Drawing change log
• KGySoft.Drawing.Wpf change log

Icon images of different resolutions and color depth can be extracted from an Icon, whereas Bitmap and Icon instances can be combined into a new Icon. PNG compressed icons are also supported.

// extracting the 256x256 image from an icon:
Bitmap bmp = Icons.Information.ExtractBitmap(new Size(256, 256));

// combining an existing icon with a bitmap:
Icon combined = myIcon.Combine(bmp);

💡 Tip: See more details at the Icons and IconExtensions classes.

As it is well known, Bitmap.SetPixel/GetPixel methods are very slow. Additionally, they do not support every pixel format. A typical solution can be to obtain a BitmapData by the LockBits method, which has further drawbacks: you need to use unsafe code and pointers, and the way you need to access the bitmap data depends on the actual PixelFormat of the bitmap.

KGy SOFT Drawing Libraries offer very fast and convenient way to overcome these issues. A managed accessor can be obtained by the GetReadableBitmapData, GetWritableBitmapData and GetReadWriteBitmapData methods:

var targetFormat = PixelFormat.Format8bppIndexed; // feel free to try other formats as well
using (Bitmap bmpSrc = Icons.Shield.ExtractBitmap(new Size(256, 256)))
using (Bitmap bmpDst = new Bitmap(256, 256, targetFormat))
{
    using (IReadableBitmapData dataSrc = bmpSrc.GetReadableBitmapData())
    using (IWritableBitmapData dataDst = bmpDst.GetWritableBitmapData())
    {
        IReadableBitmapDataRow rowSrc = dataSrc.FirstRow;
        IWritableBitmapDataRow rowDst = dataDst.FirstRow;
        do
        {
            for (int x = 0; x < dataSrc.Width; x++)
                rowDst[x] = rowSrc[x]; // works also between different pixel formats

        } while (rowSrc.MoveNextRow() && rowDst.MoveNextRow());
    }

    bmpSrc.SaveAsPng(@"c:\temp\bmpSrc.png");
    bmpDst.SaveAsPng(@"c:\temp\bmpDst.png"); // or saveAsGif/SaveAsTiff to preserve the indexed format
}

💡 Tip: See more examples with images at the GetReadWriteBitmapData extension method.

If you know the actual pixel format you can also access the raw data in a managed way. See the IReadableBitmapDataRow.ReadRaw and IWritableBitmapDataRow.WriteRaw methods for details and examples.

Not only for the native Bitmap type can you obtain a managed accessor (as described above) but you can also create a completely managed bitmap data instance by the BitmapDataFactory class. There are more benefits of using managed bitmap data: not just that they don't use any GDI or other native resources but also that they support every PixelFormat on any platform. See the BitmapDataExtensions for the available operations on bitmap data where bitmap data can be either a managed one or a managed accessor to a native Bitmap instance.

The BitmapDataFactory class has many CreateBitmapData overloads. The ones whose first parameter is Size allocate the underlying buffer by themselves, which is not directly accessible from outside. But you are also able to use predefined arrays of any primitive element type (one or two dimensional ones), and also ArraySection<T> or Array2D<T> buffers to create a managed bitmap data for.

The BitmapDataFactory class has also CreateBitmapData overloads to support unmanaged memory. This makes possible to support any bitmap representation that exposes its buffer by a pointer.

For example, this is how you can create a managed accessor for a WriteableBitmap instance commonly used in WPF/WinRT/UWP and other XAML-based environments, which exposes such a pointer:

💡 Tip: In fact, if you use the WriteableBitmap for WPF, then you can simply use the GetReadWriteBitmapData extension from the KGySoft.Drawing.Wpf package. But this is how you can access a WriteableBitmap of other XAML-based environments that do not have direct support yet.

// Though naming is different, PixelFormats.Pbgra32 is the same as KnownPixelFormat.Format32bppPArgb.
var bitmap = new WriteableBitmap(width, height, dpiX, dpiY, PixelFormats.Pbgra32, null);

// creating the managed bitmap data for WriteableBitmap:
using (var bitmapData = BitmapDataFactory.CreateBitmapData(
    bitmap.BackBuffer,
    new Size(bitmap.PixelWidth, bitmap.PixelHeight),
    bitmap.BackBufferStride,
    KnownPixelFormat.Format32bppPArgb)
{
    // Do whatever with bitmapData
}

// Actualizing changes. But see also the next example to see how to do these along with disposing.
bitmap.AddDirtyRect(new Int32Rect(0, 0, bitmap.PixelWidth, bitmap.PixelHeight));
bitmap.Unlock();

The previous example demonstrated how we can create a managed accessor for a WriteableBitmap. But it worked only because we used a pixel format that happen to have built-in support also in KGy SOFT Drawing Libraries. In fact, the libraries provide support for any custom pixel format. The CreateBitmapData methods have several overloads that allow you to specify a custom pixel format along with a couple of delegates to be called when pixels are read or written:

// Gray8 format has no built-in support
var bitmap = new WriteableBitmap(width, height, dpiX, dpiY, PixelFormats.Gray8, null);

// But we can specify how to use it
var customPixelFormat = new PixelFormatInfo { BitsPerPixel = 8, Grayscale = true };
Func<ICustomBitmapDataRow, int, Color32> getPixel =
    (row, x) => Color32.FromGray(row.UnsafeGetRefAs<byte>(x));
Action<ICustomBitmapDataRow, int, Color32> setPixel =
    (row, x, c) => row.UnsafeGetRefAs<byte>(x) = c.Blend(row.BitmapData.BackColor).GetBrightness();

// Now we specify also a dispose callback to be executed when the returned instance is disposed:
return BitmapDataFactory.CreateBitmapData(
    bitmap.BackBuffer, new Size(bitmap.PixelWidth, bitmap.PixelHeight), bitmap.BackBufferStride,
    customPixelFormat, getPixel, setPixel,
    disposeCallback: () =>
    {
        bitmap.AddDirtyRect(new Int32Rect(0, 0, bitmap.PixelWidth, bitmap.PixelHeight));
        bitmap.Unlock();
    });

Note that there are different overloads for indexed formats where you have to specify how to read/write a palette index. Please also note that these delegates work with 32-bit color structures (just like usual GetPixel/SetPixel) so wider formats will be quantized into the ARGB8888 color space (or BGRA8888, using the alternative terminology) when getting/setting pixels but this is how regular formats work, too. Anyway, you can always access the actual underlying data of whatever format by the aforementioned IReadableBitmapDataRow.ReadRaw and IWritableBitmapDataRow.WriteRaw methods.

KGy SOFT Drawing Libraries offer quantizing (reducing the number of colors of an image) and dithering (techniques for preserving the details of a quantized image) in several ways:

• The ImageExtensions.ConvertPixelFormat/BitmapDataExtensions.Clone extension methods return new Bitmap/IReadWriteBitmapData instances as the result of the quantizing/dithering.
• The BitmapExtensions.Quantize/BitmapDataExtensions.Quantize and BitmapExtensions.Dither/BitmapDataExtensions.Dither extension methods modify the original Bitmap/IReadWriteBitmapData instance.
• Some ImageExtensions.DrawInto/BitmapDataExtensions.DrawInto overloads can use quantizing and dithering when drawing different instances into each other.
• Several further extension methods in the BitmapExtensions/BitmapDataExtensions classes have an IDitherer parameter.

💡 Tip:

• For built-in quantizers see the PredefinedColorsQuantizer and OptimizedPaletteQuantizer classes. See their members for code samples and image examples.
• For built-in ditherers see the OrderedDitherer, ErrorDiffusionDitherer, RandomNoiseDitherer and InterleavedGradientNoiseDitherer classes. See their members for code samples and image examples.

See the following table for the possible results (click the images for displaying in full size):

Description	Image Example
Original image: Color hues with alpha gradient
Color hues quantized with custom 8 color palette and silver background, no dithering. The bottom part turns white because white is the nearest color to silver.
Color hues quantized with custom 8 color palette and silver background, using Bayer 8x8 dithering
Original image: Grayscale color shades
Grayscale color shades quantized with black and white palette, no dithering
Grayscale color shades quantized with black and white palette, using blue noise dithering
Original test image "Lena"
Test image "Lena" quantized with system default 8 BPP palette, no dithering
Test image "Lena" quantized with system default 8 BPP palette using Bayer 8x8 dithering
Test image "Lena" quantized with system default 8 BPP palette using Floyd-Steinberg dithering
Original test image "Cameraman"
Test image "Cameraman" quantized with black and white palette, no dithering
Test image "Cameraman" quantized with black and white palette using Floyd-Steinberg dithering

💡 Tip: Use KGy SOFT Imaging Tools from the KGySoft.Drawing.Tools repository to try image quantization and dithering in an application.

Quantizing and Dithering in KGy SOFT Imaging Tools

The KGy SOFT Drawing Libraries make possible creating high quality GIF images and animations:

• For Image types the simplest and highest-level access is provided by the ImageExtension class and its SaveAs* methods.
• Alternatively, you can use the static methods of the GifEncoder class to create animations or even high color still images. See also the AnimatedGifConfiguration class.
• To create a GIF image or animation completely manually you can instantiate the GifEncoder class that provides you the lowest-level access.

Description	Image Example
True color GIF animation. The last frame has 29,731 colors. The Granger Rainbow has been generated from an alpha gradient bitmap by this code.
Warning icon encoded as a high color GIF. It has only single bit transparency but otherwise its colors have been preserved. It consists of 18 layers and has 4,363 colors.
Test image "Lena" encoded as a high color GIF. Before encoding it was prequantized with RGB565 16-bit quantizer using Floyd-Steinberg dithering. It consists of 18 layers and has 4,451 colors. The file size is about 80% of the original PNG encoded version but could be even smaller without the dithering.

⚠️ Note: Please note that multi layered high color GIF images might be mistakenly rendered as animations by some decoders, including browsers. Still images do not contain the Netscape application extension and do not have any delays. Such images are processed properly by GDI+ on Windows, by the System.Drawing.Bitmap and Image classes and applications relying on GDI+ decoders such as Windows Paint or KGy SOFT Imaging Tools.

This repository is under the KGy SOFT License 1.0, which is a permissive GPL-like license. It allows you to copy and redistribute the material in any medium or format for any purpose, even commercially. The only thing is not allowed is to distribute a modified material as yours: though you are free to change and re-use anything, do that by giving appropriate credit. See the LICENSE file for details.