public static 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);


        //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;

    }
这个方法 红色区域报错，请那位大侠帮助看下，感激不尽