Drawing Libraries

^{(This example requires the KGySoft.Drawing.Core package and WPF. Actually you can simply use the KGySoft.Drawing.Wpf package for WPF.)}

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 happens to a 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:

// Though Gray8 format also has built-in support in KGySoft.Drawing.Core
// (see KnownPixelFormat.Format8bppGrayScale) here we pretend as if it was not supported natively.
// So this is our bitmap with the custom pixel format:
var bitmap = new WriteableBitmap(width, height, dpiX, dpiY, PixelFormats.Gray8, null);

// We need to specify a configuration that tells some info about the pixel format
// and how pixels can be got/set from known color formats.
var customConfig = new CustomBitmapDataConfig
{
    PixelFormat = new PixelFormatInfo { BitsPerPixel = 8, Grayscale = true },
    BackBufferIndependentPixelAccess = true,
    BackColor = Color.Silver.ToColor32(), // black if not specified

    // In this example we specify Color32 access but you can use other color types
    // if they fit better for the format (e.g. Color64, ColorF or their premultiplied counterparts).
    // Note that the setter blends possible alpha colors with the back color.
    RowGetColor32 = (row, x) => Color32.FromGray(row.UnsafeGetRefAs<byte>(x)),
    RowSetColor32 = (row, x, c) => row.UnsafeGetRefAs<byte>(x) =
        c.Blend(row.BitmapData.BackColor, row.BitmapData.WorkingColorSpace).GetBrightness(),

    // Now we specify also a dispose callback to be executed when the returned instance is disposed:
    DisposeCallback = () =>
    {
        bitmap.AddDirtyRect(new Int32Rect(0, 0, bitmap.PixelWidth, bitmap.PixelHeight));
        bitmap.Unlock();
    }
};

// Returning an IReadWriteBitmapData instance that wraps our native bitmap with the custom format:
return BitmapDataFactory.CreateBitmapData(
    bitmap.BackBuffer, new Size(bitmap.PixelWidth, bitmap.PixelHeight), bitmap.BackBufferStride,
    customConfig); 

💡 Tip: See also the Xamarin and MAUI examples that demonstrate how to create a bitmap data for SkiaSharp’s SKBitmap type as if there was no dedicated package for SkiaSharp.

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.