生成高质量缩略图通用函数

最新推荐文章于 2018-01-30 10:05:23 发布

takeshe

最新推荐文章于 2018-01-30 10:05:23 发布

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分类专栏： asp.net 文章标签： string image

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/// <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>
        /// <param name=""mode"">生成缩略图的方式</param>
        public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
        {
            Image originalImage = Image.FromFile(originalImagePath);

            int towidth = width;
            int toheight = height;

            int x = 0;
            int y = 0;
            int ow = originalImage.Width;
            int oh = originalImage.Height;

            switch (mode)
            {
                case ""HW""://指定高宽缩放（可能变形）
                    break;
                case ""W""://指定宽，高按比例
                    toheight = originalImage.Height * width/originalImage.Width;
                    break;
                case ""H""://指定高，宽按比例
                    towidth = originalImage.Width * height/originalImage.Height;
                    break;
                case ""Cut""://指定高宽裁减（不变形）
                    if((double)originalImage.Width/(double)originalImage.Height > (double)towidth/(double)toheight)
                    {
                        oh = originalImage.Height;
                        ow = originalImage.Height*towidth/toheight;
                        y = 0;
                        x = (originalImage.Width - ow)/2;
                    }
                    else
                    {
                        ow = originalImage.Width;
                        oh = originalImage.Width*height/towidth;
                        x = 0;
                        y = (originalImage.Height - oh)/2;
                    }
                    break;
                default :
                    break;
            }

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

//新建一个画板
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(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 Rectangle(0, 0, towidth, toheight),
                new Rectangle(x, y, ow,oh),
                GraphicsUnit.Pixel);

            try
            {
                //以jpg格式保存缩略图
                bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
            }
            catch(System.Exception e)
            {
                throw e;
            }
            finally
            {
                originalImage.Dispose();
                bitmap.Dispose();
                g.Dispose();
            }
        }