DrawImage 按指定尺寸剪切图片

Question

public void SImage(System.Drawing.Image sourceImage, int w, int h, string path)
    {
        int x = 0;
        int y = 0;
        int ow = sourceImage.Width;
        int oh = sourceImage.Height;
        if (ow > oh)
        {
            ow = (h * ow) / oh;
            oh = h;
            x = (ow - w) / 2;
        }
        else
        {
            oh = (w * oh) / ow;
            ow = w;
            y = (oh - h) / 2;
        }
        System.Drawing.Image.GetThumbnailImageAbort callBack = new System.Drawing.Image.GetThumbnailImageAbort(this.ThumbnailCallback);
        System.Drawing.Image smallImage = sourceImage.GetThumbnailImage(ow, oh, callBack, IntPtr.Zero);
        sourceImage.Save(path, ImageFormat.Jpeg);
        Bitmap bmp = new Bitmap(w, h);
        Graphics gph = Graphics.FromImage(bmp);
        Rectangle imageRectangle = new Rectangle(-x, -y, ow, oh);
        gph.DrawImage(sourceImage, imageRectangle);
        bmp.Save(path, ImageFormat.Jpeg);        
    }按指定尺寸剪切图片，比如一个大小为 1027*768 的图，把原图等比列缩小宽度为300后再把缩小的图片以300*200的尺寸剪切下来保存。以上方法做的图总是被拉开了。没的剪切，只是把原图缩小后又拉升到300*200

Answer 1

/// <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) 
     { 
         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 
         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), 
             new System.Drawing.Rectangle(x, y, ow, oh), 
             System.Drawing.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(); 
         } 
     }

Answer 2

谢谢楼上，Cut很好用，但是以是把上下边都剪切了，我还想问一下，如果我以上边对齐开始剪切，剪切掉下边多的不要，这样如何操作。