static byte To4Bits(ByteRgb c)
{
var r = (c.R & 0x80) >> 7;
var g = (c.G & 0x80) >> 7;
var b = (c.B & 0x80) >> 7;
return((byte)((b << 2) | (g << 1) | r));
}
private static void UpdatePixel(List <ByteRgb[]> pixels, int x, int y, IntRgb qerr, float fraction)
{
var col = pixels[y][x];
var qr = (int)(qerr.R * fraction);
var qg = (int)(qerr.G * fraction);
var qb = (int)(qerr.B * fraction);
var newCol = ByteRgb.FromArgb(0, (col.R + qr).ToByte(),
(col.G + qg).ToByte(), (col.B + qb).ToByte());
pixels[y][x] = newCol;
}
public static void Dither(List <ByteRgb[]> array, int width, int height)
{
for (var y = 0; y < height; ++y)
{
for (var x = 0; x < width; ++x)
{
var oldPixel = array[y][x];
var nr = oldPixel.R >= 128 ? 255 : 0;
var ng = oldPixel.G >= 128 ? 255 : 0;
var nb = oldPixel.B >= 128 ? 255 : 0;
var newPixel = ByteRgb.FromArgb(0, (byte)nr, (byte)ng, (byte)nb);
array[y][x] = newPixel;
// Compute quantization error
IntRgb qerr;
qerr.R = oldPixel.R - newPixel.R;
qerr.G = oldPixel.G - newPixel.G;
qerr.B = oldPixel.B - newPixel.B;
if (x + 1 < width)
{
UpdatePixel(array, x + 1, y, qerr, 7.0f / 16.0f);
}
if (((x - 1) >= 0) && ((y + 1) < height))
{
UpdatePixel(array, x - 1, y + 1, qerr, 3.0f / 16.0f);
}
if (((y + 1) < height))
{
UpdatePixel(array, x, y + 1, qerr, 5.0f / 16.0f);
}
if (((x + 1) < width) && ((y + 1) < height))
{
UpdatePixel(array, x + 1, y + 1, qerr, 1.0f / 16.0f);
}
}
}
}
