C#實現圖片生成縮略圖

1，判斷圖片的寬和高的比例，然后進行縮放，以便于使縮略圖不變形。
2，DrawImage方法為縮略圖繪制邊框，這樣，瀏覽起來比較美觀。
3，調用Save方法將生成的縮略圖保存到指定的目錄下。

    private void MakeThumbnail(string sourcePath, string newPath, int width, int height)
    {
        System.Drawing.Image ig = System.Drawing.Image.FromFile(sourcePath);
        int towidth = width;
        int toheight = height;
        int x = 0;
        int y = 0;
        int ow = ig.Width;
        int oh = ig.Height;
        if ((double)ig.Width / (double)ig.Height > (double)towidth / (double)toheight)
        {
            oh = ig.Height;
            ow = ig.Height * towidth / toheight;
            y = 0;
            x = (ig.Width - ow) / 2;


    }
    else
    {
        ow = ig.Width;
        oh = ig.Width * height / towidth;
        x = 0;
        y = (ig.Height - oh) / 2;
    }
    System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
    System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);
    g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
    g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
    g.Clear(System.Drawing.Color.Transparent);
    g.DrawImage(ig, new System.Drawing.Rectangle(0, 0, towidth, toheight), new System.Drawing.Rectangle(x, y, ow, oh), System.Drawing.GraphicsUnit.Pixel);
    try
    {
        bitmap.Save(newPath, System.Drawing.Imaging.ImageFormat.Jpeg);
    }
    catch (Exception ex)
    {
        throw ex;
    }
    finally
    {
        ig.Dispose();
        bitmap.Dispose();
        g.Dispose();
    }

}</pre>