在.net中使用GDI+来提高gif图片画质，这就是“Octree” 算法。“Octree”算法允许我们插入自己的算法来量子化我们的图像。

　　使用octreequantizer很方便：

system.drawing.bitmap b = new System.Drawing.Bitmap(“c:\original_image.gif“);
　　System.Drawing.Image thmbnail = b.GetThumbnailImage(100,75,null,new IntPtr());
　　OctreeQuantizer quantizer = new OctreeQuantizer ( 255 , 8 ) ;
　　using ( Bitmap quantized = quantizer.Quantize ( thmbnail ) )
　　{
　　quantized.Save(“c:\thumnail.gif“, System.Drawing.Imaging.ImageFormat.Gif);
　　}
　　octreequantizer grayquantizer = new GrayscaleQuantizer ( ) ;
　　using ( Bitmap quantized = grayquantizer.Quantize ( thmbnail ) )
　　{
　　quantized.Save(“c:\thumnail.gif“, System.Drawing.Imaging.ImageFormat.Gif);
　　}