private static int FindNearestPal(RGBQUAD inputPal, List <RGBQUAD> palList, Dictionary <RGBQUAD, int> additionalPalMap)
{
if (additionalPalMap.TryGetValue(inputPal, out var addPal))
{
return(addPal);
}
var ind = palList
.IndexOf(palList
.OrderBy(x =>
Math.Sqrt(Math.Pow(x.rgbBlue - inputPal.rgbBlue, 2) + Math.Pow(x.rgbGreen - inputPal.rgbGreen, 2) + Math.Pow(x.rgbRed - inputPal.rgbRed, 2)))
.First());
additionalPalMap[inputPal] = ind;
return(ind);
}
private static void EncodeColorMapWithAlpha(byte[] decodedData, BITMAPINFOHEADER bmi, ProcessData processData, out byte[] encodedData, out byte[] alphaData, out RGBQUAD[] pal)
{
//must be padded to 4 bytes
uint rgbStride = (uint)((bmi.biWidth * processData.Decoding.Bmi.biBitCount / 8 + 3) & ~3);
alphaData = new byte[processData.Decoding.Bmi.biBitCount == 8 ? bmi.biHeight * bmi.biWidth : processData.Decoding.AlphaBuff.Length];
encodedData = new byte[processData.Decoding.Bmi.biBitCount == 8 ? bmi.biHeight * rgbStride : processData.Decoding.EncodedData.Length];
var palList = useExistingPal ? processData.Decoding?.PalArray.ToList() : new List <RGBQUAD>();
var additionalPalMap = new Dictionary <RGBQUAD, int>();
for (long y = 0; y < bmi.biHeight; y++)
{
uint alphaLineIndex = (uint)((bmi.biHeight - y - 1) * bmi.biWidth);
uint rgbaLineIndex = (uint)(y * bmi.biWidth * 4);
long rgbLineIndex = y * rgbStride;
for (long x = 0; x < bmi.biWidth; x++)
{
long blueIndex = rgbaLineIndex + x * 4 + 0;
if (processData.Decoding.Bmi.biBitCount == 8)
{
var newPal = new RGBQUAD
{
rgbBlue = decodedData[blueIndex],
rgbGreen = decodedData[blueIndex + 1],
rgbRed = decodedData[blueIndex + 2]
};
var palIndex = palList.IndexOf(newPal);
if (palIndex == -1)
{
palIndex = useExistingPal ? FindNearestPal(newPal, palList, additionalPalMap) : GetPal(newPal, palList, additionalPalMap);
}
encodedData[y * rgbStride + x] = (byte)palIndex;
}
else
{
encodedData[rgbLineIndex + x * 3] = decodedData[blueIndex];
encodedData[rgbLineIndex + x * 3 + 1] = decodedData[blueIndex + 1];
encodedData[rgbLineIndex + x * 3 + 2] = decodedData[blueIndex + 2];
}
alphaData[alphaLineIndex + x] = decodedData[blueIndex + 3];
}
}
if (palList.Count < 256)
{
palList.AddRange(Enumerable.Repeat(new RGBQUAD(), 256 - palList.Count));
}
pal = palList.ToArray();
}