public static void RemapPalette(FreeImageBitmap bitmap, Palette newPalette)
{
if (bitmap.ColorDepth > 8)
{
bitmap.Quantize(FREE_IMAGE_QUANTIZE.FIQ_WUQUANT, 256, newPalette);
}
var sourcePal = bitmap.Palette.AsArray.Select(c => c.uintValue).ToArray();
var destPal = newPalette.AsArray.Select(c => c.uintValue).ToArray();
int[] srcToDest = new int[256];
for (int i = 0; i < 256; i++)
{
srcToDest[i] = -1;
}
//first map identical colors
{
Dictionary <int, int> rgbToPaletteIndex = new Dictionary <int, int>();
for (int i = 0; i < 256; i++)
{
int c = (int)(destPal[i] & 0xFFFFFF);
if (!rgbToPaletteIndex.ContainsKey(c))
{
rgbToPaletteIndex.Add(c, i);
}
}
for (int i = 0; i < 256; i++)
{
int c = (int)(sourcePal[i] & 0xFFFFFF);
if (rgbToPaletteIndex.ContainsKey(c))
{
srcToDest[i] = rgbToPaletteIndex[c];
}
}
}
//map remaining colors
{
for (int i = 0; i < 256; i++)
{
if (srcToDest[i] == -1)
{
int c = (int)(sourcePal[i] & 0xFFFFFF);
int minDistance = int.MaxValue;
int minIndex = -1;
for (int j = 0; j < 256; j++)
{
int c2 = (int)(destPal[j] & 0xFFFFFF);
int distance = GetDistance(c, c2);
if (distance < minDistance)
{
minDistance = distance;
minIndex = j;
}
}
srcToDest[i] = minIndex;
}
}
}
byte[] sequence = new byte[256];
byte[] srcToDestByte = new byte[256];
{
for (int i = 0; i < 256; i++)
{
sequence[i] = (byte)i;
srcToDestByte[i] = (byte)srcToDest[i];
}
}
bitmap.ApplyPaletteIndexMapping(sequence, srcToDestByte, 256, false);
bitmap.Palette.AsArray = newPalette.AsArray;
}
