GDI+ 发生一般性错误解决办法

错误的代码g对象继续占用 未释放资源 如果路径不一样 没问题 相同路径 获取图片进行

缩略会造成GDI错误

/// <summary>
        /// 生成缩略图
        /// </summary>
        /// <param name="originalImagePath">源图路径（物理路径）</param>
        /// <param name="thumbnailPath">缩略图路径（物理路径）</param>
        /// <param name="width">缩略图宽度</param>
        /// <param name="height">缩略图高度</param> 

        public void CreateMinImage(string originalImagePath, string thumbnailPath, int width, int height)
        {
            System.Drawing.Image originalImage = System.Drawing.Image.FromFile(HttpContext.Current.Server.MapPath(originalImagePath));

            int towidth = width;
            int toheight = height;

            int ow = originalImage.Width;
            int oh = originalImage.Height;

            //新建一个bmp图片
            System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);

            //新建一个画板
            System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);


            //设置高质量插值法
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

            //设置高质量,低速度呈现平滑程度
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

            //清空画布并以透明背景色填充
            g.Clear(System.Drawing.Color.Transparent);

            //在指定位置并且按指定大小绘制原图片的指定部分
            g.DrawImage(originalImage, new System.Drawing.Rectangle(0, 0, towidth, toheight));

            try
            {
                //以jpg格式保存缩略图
                string FileExt = Path.GetFileNameWithoutExtension(originalImagePath);
//这里报错               bitmap.Save(HttpContext.Current.Server.MapPath(thumbnailPath) + FileExt + ".jpg", System.Drawing.Imaging.ImageFormat.Jpeg);
            }
            catch (System.Exception e)
            {
                throw e;
            }
            finally
            {
                originalImage.Dispose();
                bitmap.Dispose();
                g.Dispose();
            }

        }

//修改后的代码
public void CreateMinImageAndDel(string originalImagePath, string thumbnailPath, int width, int height)
        {
            Graphics draw = null;
            string FileExt = "";

            System.Drawing.Image originalImage = System.Drawing.Image.FromFile(HttpContext.Current.Server.MapPath(originalImagePath));

            int towidth = width;
            int toheight = height;

            int ow = originalImage.Width;
            int oh = originalImage.Height;

            //新建一个bmp图片
            System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
            System.Drawing.Image bitmap2 = new System.Drawing.Bitmap(towidth, toheight);
            //新建一个画板
            System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);


            //设置高质量插值法
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

            //设置高质量,低速度呈现平滑程度
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

            //清空画布并以透明背景色填充
            g.Clear(System.Drawing.Color.Transparent);

            //在指定位置并且按指定大小绘制原图片的指定部分
            g.DrawImage(originalImage, new System.Drawing.Rectangle(0, 0, towidth, toheight));

            try
            {
                //以jpg格式保存缩略图
                FileExt = Path.GetFileNameWithoutExtension(originalImagePath);
　　　　　　　　　　//用新建立的image对象拷贝bitmap对象 让g对象可以释放资源
                draw = Graphics.FromImage(bitmap2);
                draw.DrawImage(bitmap, 0, 0);

            }
            catch (System.Exception e)
            {
                throw e;
            }
            finally
            {
                originalImage.Dispose();
                bitmap.Dispose();
                g.Dispose();
　　　　　　　　　　//保存调整在这里即可
                bitmap2.Save(HttpContext.Current.Server.MapPath(thumbnailPath) + FileExt + ".jpg", System.Drawing.Imaging.ImageFormat.Jpeg);
            }
        }