/// <summary>
/// Indexed alpha: grayscale indexed 255 color image with single color gradient
/// Transparency is determined by index value
/// </summary>
/// <param name="image"></param>
/// <returns></returns>
private static Rgba32[] ConvertIndexedAlpha(IndexedColor256Image image)
{
var size = image.Size;
var pixels = new Rgba32[size];
ref var color = ref image.Palette[IndexedAlphaColorIndex];
/// <summary>
/// Convert an indexed 256 color image to an Rgba32 image
/// </summary>
/// <param name="image"></param>
/// <returns></returns>
private static Rgba32[] ConvertNormal(IndexedColor256Image image)
{
var size = image.Size;
var pixels = new Rgba32[size];
foreach (var i in Enumerable.Range(0, size))
{
image.Palette[image.Pixels[i]].ToRgba32(ref pixels[i]);
}
return(pixels);
}
/// <summary>
/// Alpha test: convert all indices to their color except index 255, which is converted as fully transparent
/// </summary>
/// <param name="image"></param>
/// <returns></returns>
private static Rgba32[] ConvertAlphaTest(IndexedColor256Image image)
{
var size = image.Size;
var pixels = new Rgba32[size];
foreach (var i in Enumerable.Range(0, size))
{
var index = image.Pixels[i];
if (index != AlphaTestTransparentIndex)
{
image.Palette[index].ToRgba32(ref pixels[i]);
}
else
{
//RGB values default to 0 in array initializer
pixels[i].A = 0;
}
}
return(pixels);
}