Filling with a transparent color does not work as expected

[equinox2k]

Using the following on an existing image to clear it does nothing...

imageToProcess.Mutate(i => i.Fill(SixLabors.ImageSharp.Color.Transparent));

However doing the following works...

var graphicsOptions = new GraphicsOptions
{
    AlphaCompositionMode = PixelAlphaCompositionMode.Clear
};
var rectangle = new RectangleF(0, 0, imageToProcess.Width, imageToProcess.Height);                
imageToProcess.Mutate(i => i.Fill(graphicsOptions, SixLabors.ImageSharp.Color.Transparent, rectangle));

I assume the defaults should of been good enough for the first to work

[arakis]

Here is a little extension that makes life easier:

public static class ImageExtensions
{
    public static void Clear(this IImageProcessingContext source, Color color)
    {
        var graphicsOptions = new GraphicsOptions
        {
            AlphaCompositionMode = PixelAlphaCompositionMode.Clear
        };
        var size = source.GetCurrentSize();
        source.Fill(graphicsOptions, color, new Rectangle(0, 0, size.Width, size.Height));
    }
}

Just call it:

imageToProcess.Mutate(i => i.Clear(Color.Transparent);

[tocsoft]

Untill we add our own set of Clear() apis the most efficient way to do this as of now is

public static class ImageExtensions
{
    public static void Clear(this IImageProcessingContext source, Color color)
    {
        var graphicsOptions = new GraphicsOptions
        {
            AlphaCompositionMode = PixelAlphaCompositionMode.Src,
            ColorBlendingMode = PixelColorBlendingMode.Normal
        };
        source.Fill(graphicsOptions, color);
    }
}