截取图片的某个部分(C#源代码)

最新推荐文章于 2017-07-06 15:44:00 发布

转载最新推荐文章于 2017-07-06 15:44:00 发布 · 227 阅读

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原文链接：http://www.cnblogs.com/snigoal/archive/2008/03/23/1118209.html

本文介绍了两种从图片中截取特定矩形区域的方法：一种是通过逐像素操作(set/get pixel)实现，另一种则利用了Graphics类的DrawImage方法。后者因效率较高而被推荐使用。

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方法一(get/set pixel)

核心语句：

resultBitmap.SetPixel(x, y, sourceBitmap.GetPixel(offsetX + x, offsetY+y))

代码

1 /// <summary>
2 /// get a certain rectangle part of a known graphic
3 /// </summary>
4 /// <param name="bitmapPathAndName">path and name of the source graphic</param>
5 /// <param name="width">width of the part graphic</param>
6 /// <param name="height">height of the part graphic</param>
7 /// <param name="offsetX">the width offset in the source graphic</param>
8 /// <param name="offsetY">the height offset in the source graphic</param>
9 /// <returns>wanted graphic</returns>
10 public Bitmap GetPartOfImage(string bitmapPathAndName, int width, int height,int offsetX,int offsetY)
11 {
12 Bitmap sourceBitmap = new Bitmap(bitmapPathAndName);
13 Bitmap resultBitmap = new Bitmap(width, height);
14 for (int x = 0; x < width; x++)
15 {
16 for (int y = 0; y < height; y++)
17 {
18 if (offsetX + x < sourceBitmap.Size.Width & offsetY + y < sourceBitmap.Size.Height)
19 {
20 resultBitmap.SetPixel(x, y, sourceBitmap.GetPixel(offsetX + x, offsetY+y));
21 }
22 }
23 }
24 return resultBitmap;
25 }

该方法速度较慢

方法二(graphics.drawimage)

核心代码：

Graphics g = Graphics.FromImage(resultBitmap)

g.DrawImage(sourceBitmap, resultRectangle, sourceRectangle, GraphicsUnit.Pixel)

代码

1 /// <summary>
2 /// get a certain rectangle part of a known graphic
3 /// </summary>
4 /// <param name="bitmapPathAndName">path and name of the source graphic</param>
5 /// <param name="width">width of the part graphic</param>
6 /// <param name="height">height of the part graphic</param>
7 /// <param name="offsetX">the width offset in the source graphic</param>
8 /// <param name="offsetY">the height offset in the source graphic</param>
9 /// <returns>wanted graphic</returns>
10 public Bitmap GetPartOfImage(string bitmapPathAndName, int width, int height, int offsetX, int offsetY)
11 {
12 Bitmap sourceBitmap = new Bitmap(bitmapPathAndName);
13 Bitmap resultBitmap = new Bitmap(width, height);
14 using (Graphics g = Graphics.FromImage(resultBitmap))
15 {
16 Rectangle resultRectangle = new Rectangle(0, 0, Width, height);
17 Rectangle sourceRectangle = new Rectangle(0+offsetX, 0+offsetY, Width, height);
18 g.DrawImage(sourceBitmap, resultRectangle, sourceRectangle, GraphicsUnit.Pixel);
19 }
20 return resultBitmap;
21 }

速度较快，可完全鄙视掉方法一

转载于:https://www.cnblogs.com/snigoal/archive/2008/03/23/1118209.html