public async Task <byte[]> ApplyAsync(ISffPngImageHeader imageHeader, byte[] imageData, IPalette palette)
{
// (Scanline filter byte + imageHeader.Width * 4 RGBA bytes) * imageHeader.Height == imageData.Length
if ((1 + imageHeader.Width * 4) * imageHeader.Height == imageData.Length)
{
// Already in RGBA format
return(imageData);
}
if (palette == null)
{
throw new ArgumentNullException($"Palette is required to decode PNG image.");
}
var coloredImage = new List <byte>();
for (var index = 0; index < imageData.Length; ++index)
{
var paletteIndex = imageData[index];
// For scanline filter type we don't want to perform colorization
if (index == 0 || index % imageHeader.BytesInRow == 0)
{
coloredImage.Add(paletteIndex);
continue;
}
var color = palette.ElementAt(paletteIndex);
coloredImage.Add(color.Red);
coloredImage.Add(color.Green);
coloredImage.Add(color.Blue);
coloredImage.Add(color.Alpha);
}
return(coloredImage.ToArray());
}