Graphics.DrawImage gif图片失真怎么办？

Question

如题，用Graphics.DrawImage 切图，就是截取一个图片上指定部分的图片draw到另一个图片上，gif失真，请前辈们指教啊，

Answer 1

我不缩放啊，生成图片部分的代码
using (System.Drawing.Image oImg = System.Drawing.Image.FromFile(sImagePath))
            {
                //创建图片
                System.Drawing.Bitmap oBit = new System.Drawing.Bitmap(iPartWidth, iPartHeight);
                System.Drawing.Graphics oPic = System.Drawing.Graphics.FromImage(oBit);
                //目标位置
                System.Drawing.Rectangle rDest = new System.Drawing.Rectangle(
                    new System.Drawing.Point(iPartStartPointX, iPartStartPointY),
                    new System.Drawing.Size(iPartWidth, iPartHeight));
                //原图位置（默认从原图中截取的图片大小等于目标图片的大小）
                System.Drawing.Rectangle rOrig = new System.Drawing.Rectangle(
                    new System.Drawing.Point(iOrigStartPointX, iOrigStartPointY),
                    new System.Drawing.Size(iPartWidth, iPartHeight));
                //生成图片
                System.Drawing.Brush bh = new System.Drawing.SolidBrush(System.Drawing.Color.White);
                oPic.FillRectangle(bh, rDest);
                oPic.DrawImage(oImg, rDest, rOrig, System.Drawing.GraphicsUnit.Pixel);
                oImg.Dispose();
                //检查文件
                if (System.IO.File.Exists(sPath))
                {
                    System.IO.File.SetAttributes(sPath, System.IO.FileAttributes.Normal);
                    System.IO.File.Delete(sPath);
                }
                //保存文件
                switch (sCode.ToLower())
                {
                    case ".gif": oBit.Save(sPath, System.Drawing.Imaging.ImageFormat.Gif); break;
                    case ".png": oBit.Save(sPath, System.Drawing.Imaging.ImageFormat.Png); break;
                    case ".bmp": oBit.Save(sPath, System.Drawing.Imaging.ImageFormat.Bmp); break;
                    default: oBit.Save(sPath, System.Drawing.Imaging.ImageFormat.Jpeg); break;
                }
            }