截取图片的某个部分(C#源代码)
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
