无损图片缩放

public static void SaveThumbnail(Bitmap originBitmap, int width, int height, string filename)
        {
            using (var newImage = new Bitmap(width, height))
            {
                using (var graphic = GetGraphic(originBitmap, newImage))
                {
                    graphic.DrawImage(originBitmap, 0, 0, width, height);

                    
                    ImageCodecInfo[] codecs = ImageCodecInfo.GetImageEncoders();
                    ImageCodecInfo ici = null;
                    foreach (ImageCodecInfo codec in codecs)
                    {
                        if (codec.MimeType.IndexOf("png") > -1)
                            ici = codec;
                    }
                    EncoderParameters encoderParams = new EncoderParameters();
                    long[] qualityParam = new long[1];                    
                    qualityParam[0] = 100;
                    EncoderParameter encoderParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qualityParam);
                    encoderParams.Param[0] = encoderParam;

                    newImage.Save(filename, ici, encoderParams);
                }
            }
        }

        private static Graphics GetGraphic(Image originImage, Bitmap newImage)
        {
            newImage.SetResolution(originImage.HorizontalResolution, originImage.VerticalResolution);
            var graphic = Graphics.FromImage(newImage);
            graphic.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
            graphic.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
            graphic.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality;
            graphic.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
            return graphic;
        }

看了dudu的，但是调用报错，稍作修改