asp.net 高品質縮圖

 

 

using System.Drawing;

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調用：  MakeThumbnail("C:\\sdf.JPG", "C:\\sdfsss.JPG", 300, 40, "W");

 

 //****************************************************************************************產生縮圖
    /// <summary>
    /// 產生縮圖
    /// </summary>
    /// <param name="originalImagePath">源圖路徑（實體路徑）</param>
    /// <param name="thumbnailPath">縮圖路徑（實體路徑）</param>
    /// <param name="width">縮圖寬度</param>
    /// <param name="height">縮圖高度</param>
    /// <param name="mode">產生縮圖的方式</param>    
    public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
    {

        System.Drawing.Image originalImage = System.Drawing.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"://指定高寬縮放（可能變形）                
                break;
            case "W"://指定寬，高按比例                    
                toheight = originalImage.Height * width / originalImage.Width;
                break;
            case "H"://指定高，寬按比例
                towidth = originalImage.Width * height / originalImage.Height;
                break;
            case "Cut"://指定高寬裁減（不變形）                
                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;
        }

        //建立一個bmp圖片
        System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);

        //建立一個畫板
        Graphics g = System.Drawing.Graphics.FromImage(bitmap);

        //設定高品質插值法
        g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

        //設定高品質,低速度呈現平滑程度
        g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

        //清空畫布並以透明背景色填充
        g.Clear(Color.Transparent);

        //在指定位置並且按指定大小繪製原圖片的指定部分
        g.DrawImage(originalImage, new System.Drawing.Rectangle(0, 0, towidth, toheight),
            new System.Drawing.Rectangle(x, y, ow, oh),
            GraphicsUnit.Pixel);

        try
        {
            //以jpg格式儲存縮圖
            bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
        }
        catch (System.Exception e)
        {
            throw e;
        }
        finally
        {
            originalImage.Dispose();
            bitmap.Dispose();
            g.Dispose();
        }
    }