private static IEnumerable<byte[]> indexedPixels(ImageBuffer image, Pixel[] lookups, int alphaThreshold, int maxColors, PaletteColorHistory[] paletteHistogram)
{
int pixelsCount = image.Image.Width * image.Image.Height;
var lineIndexes = new byte[(int)System.Math.Ceiling(image.Image.Width / System.Math.Log(256.0, maxColors))];
PaletteLookup lookup = new PaletteLookup(lookups);
--maxColors;
foreach (var pixelLine in image.PixelLines)
{
for (int pixelIndex = 0; pixelIndex < pixelLine.Length; pixelIndex++)
{
Pixel pixel = pixelLine[pixelIndex];
byte bestMatch = (byte)maxColors;
if (pixel.Alpha > alphaThreshold)
{
bestMatch = lookup.GetPaletteIndex(pixel);
paletteHistogram[bestMatch].AddPixel(pixel);
}
switch (maxColors)
{
case 256 - 1:
lineIndexes[pixelIndex] = bestMatch;
break;
case 16 - 1:
if (pixelIndex % 2 == 0) { lineIndexes[pixelIndex / 2] = (byte)(bestMatch << 4); }
else { lineIndexes[pixelIndex / 2] |= (byte)(bestMatch & 0x0F); }
break;
case 2 - 1:
if (pixelIndex % 8 == 0) { lineIndexes[pixelIndex / 8] = (byte)(bestMatch << 7); }
else { lineIndexes[pixelIndex / 8] |= (byte)((bestMatch & 0x01) << (7 - (pixelIndex % 8))); }
break;
}
}
yield return lineIndexes;
}
}
public Image QuantizeImage(Bitmap image, int alphaThreshold = 10, int alphaFader = 70, int maxColors = 256)
{
var colorCount = maxColors;
ImageBuffer buffer = new ImageBuffer(image);
var moments = BuildHistogram(buffer, alphaThreshold, alphaFader);
CalculateMoments(moments);
var cubes = SplitData(ref colorCount, maxColors, moments);
var lookups = BuildLookups(cubes, moments);
return GetQuantizedImage(buffer, colorCount, maxColors, lookups, alphaThreshold);
}
internal override Image GetQuantizedImage(ImageBuffer image, int colorCount, int maxColors, Pixel[] lookups, int alphaThreshold)
{
PixelFormat pf;
switch (maxColors)
{
case 256: pf = PixelFormat.Format8bppIndexed; break;
case 16: pf = PixelFormat.Format4bppIndexed; break;
case 2: pf = PixelFormat.Format1bppIndexed; break;
default: throw new QuantizationException(string.Format("The target amount of colors is not supported. Requested {0} colors.", maxColors));
}
var result = new Bitmap(image.Image.Width, image.Image.Height, pf);
var resultBuffer = new ImageBuffer(result);
var paletteHistogram = new PaletteColorHistory[colorCount + 1];
resultBuffer.UpdatePixelIndexes(indexedPixels(image, lookups, alphaThreshold, maxColors, paletteHistogram));
result.Palette = BuildPalette(result.Palette, paletteHistogram);
return result;
}
internal abstract Image GetQuantizedImage(ImageBuffer image, int colorCount, int maxColors, Pixel[] lookups, int alphaThreshold);
private static ColorMoment[, , ,] BuildHistogram(ImageBuffer sourceImage, int alphaThreshold, int alphaFader)
{
var moments = new ColorMoment[SideSize, SideSize, SideSize, SideSize];
foreach(var pixelLine in sourceImage.PixelLines)
{
for (int pixelIndex = 0; pixelIndex < pixelLine.Length; pixelIndex++)
{
Pixel pixel = pixelLine[pixelIndex];
byte pixelAlpha = pixel.Alpha;
if (pixelAlpha > alphaThreshold)
{
if (pixelAlpha < 255)
{
var alpha = pixel.Alpha + (pixel.Alpha % alphaFader);
pixelAlpha = (byte)(alpha > 255 ? 255 : alpha);
}
byte pixelRed = pixel.Red;
byte pixelGreen = pixel.Green;
byte pixelBlue = pixel.Blue;
pixelAlpha = (byte)((pixelAlpha >> SidePixShift) + 1);
pixelRed = (byte)((pixelRed >> SidePixShift) + 1);
pixelGreen = (byte)((pixelGreen >> SidePixShift) + 1);
pixelBlue = (byte)((pixelBlue >> SidePixShift) + 1);
moments[pixelAlpha, pixelRed, pixelGreen, pixelBlue].Add(pixel);
}
}
}
return moments;
}
