Add files via upload

Author: mcychan

nQuant.Master/GilbertCurve.cs

@@ -227,10 +227,10 @@ private void DiffusePixel(int x, int y)
 			int a_pix = (int)Math.Min(Byte.MaxValue, Math.Max(error[3], 0.0));
 
 			Color c2 = Color.FromArgb(a_pix, r_pix, g_pix, b_pix);
-			if (saliencies != null && dither && !sortedByYDiff && (!m_hasAlpha || Math.Abs(pixel.A - a_pix) < (.5 * margin)))
+			if (saliencies != null && dither && !sortedByYDiff && (!m_hasAlpha || pixel.A < a_pix))
 			{
-				if (palette.Length >= 256 && saliencies[bidx] > .99f)
-					qPixels[bidx] = ditherable.DitherColorIndex(palette, c2.ToArgb(), bidx);
+				if ((palette.Length >= 256 && saliencies[bidx] > .99f) || (m_hasAlpha && (pixel.A - a_pix) < (.5 * margin)))
+                    qPixels[bidx] = ditherable.DitherColorIndex(palette, c2.ToArgb(), bidx);
 				else
 					qPixels[bidx] = DitherPixel(x, y, c2, beta);
 			}