在做项目时发现图片CMYK模式无法显示，

下面使用将Image重新绘制为Format24bppRgb的方式来解决此问题： 

using

 System.Drawing; 

using System.Drawing.Drawing2D;

using System.Drawing.Imaging;

protected void Button1_Click(object sender, EventArgs e)

        {

            if (FileUpload1.HasFile)

            {

                SavePostedImage(FileUpload1.PostedFile, FileUpload1.FileName, 1000,1000);

            }

        }

        public void SavePostedImage(HttpPostedFile postedFile, string destFileName, int maxHeight, int maxWidth)

        {

            System.Drawing.Imaging.ImageFormat imgFormat;

            if (destFileName.ToLower().EndsWith("jpg"))

            {

                imgFormat = ImageFormat.Jpeg;

            }

            else //这里可以加更多选项，比如png,gif,tif....

            {

                imgFormat = ImageFormat.Gif;

            }

            Bitmap bmp = new Bitmap(postedFile.InputStream);

            if (IsCMYK(bmp))

            {

                bmp = ConvertCMYK(bmp);

            }

            if ((bmp.HorizontalResolution > 72) || (bmp.VerticalResolution > 72))

            {

                bmp.SetResolution(72, 72);

            }

            Bitmap saveBmp;

            if ((bmp.Height > maxHeight) || (bmp.Width > maxWidth))

            {

                Double heightRatio = Convert.ToDouble(maxHeight) / Convert.ToDouble(bmp.Height);

                Double widthRatio = Convert.ToDouble(maxWidth) / Convert.ToDouble(bmp.Width);

                Double scaleRatio;

                if (heightRatio > widthRatio)

                {

                    scaleRatio = widthRatio;

                }

                else

                {

                    scaleRatio = heightRatio;

                }

                int height = Convert.ToInt32(bmp.Height * scaleRatio);

                int width = Convert.ToInt32(bmp.Width * scaleRatio);

                saveBmp = new Bitmap(bmp, width, height);

            }

            else

            {

                saveBmp = new Bitmap(bmp);

            }

            bmp.Dispose();

            saveBmp.Save(Server.MapPath("~/") + destFileName, imgFormat);

            saveBmp.Dispose();

            postedFile.InputStream.Close();

        }

        public string GetImageFlags(System.Drawing.Image img)

        {

            ImageFlags FlagVals = (ImageFlags)Enum.Parse(typeof(ImageFlags), img.Flags.ToString());

            return FlagVals.ToString();

        }

        public bool IsCMYK(System.Drawing.Image img)

        {

            bool isCmyk;

            if ((GetImageFlags(img).IndexOf("Ycck") > -1) || (GetImageFlags(img).IndexOf("Cmyk") > -1))

            { isCmyk = true; }

            else

            { isCmyk = false; }

            return isCmyk;

        }

        public Bitmap ConvertCMYK(Bitmap bmp)

        {

            Bitmap tmpBmp = new Bitmap(bmp.Width, bmp.Height, PixelFormat.Format24bppRgb);

            Graphics g = Graphics.FromImage(tmpBmp);

            g.CompositingQuality = CompositingQuality.HighQuality;

            g.SmoothingMode = SmoothingMode.HighQuality;

            g.InterpolationMode = InterpolationMode.HighQualityBicubic;

            Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);

            // 将CMYK图片重绘一遍,此时GDI+自动将CMYK格式转换为RGB了

            g.DrawImage(bmp, rect);

            Bitmap returnBmp = new Bitmap(tmpBmp);

            g.Dispose();

            tmpBmp.Dispose();

            bmp.Dispose();

            return returnBmp;

        } 

    }下面使用将Image重新绘制为Format24bppRgb的方式来解决此问题：。