Obj-c代码
1. @interface UIImage(UIImageScale)
2. -(UIImage*)getSubImage:(CGRect)rect;
3. -(UIImage*)scaleToSize:(CGSize)size;
4. @end
5.
6. @implementation UIImage(UIImageScale)
7.
8. //截取部分图像
9. -(UIImage*)getSubImage:(CGRect)rect
10. {
11. CGImageRef subImageRef = CGImageCreateWithImageInRect(self.CGImage, rect);
12. CGRect smallBounds = CGRectMake(0, 0, CGImageGetWidth(subImageRef), CGImageGetHeight(subImageRef));
13.
14. UIGraphicsBeginImageContext(smallBounds.size);
15. CGContextRef context = UIGraphicsGetCurrentContext();
16. CGContextDrawImage(context, smallBounds, subImageRef);
17. UIImage* smallImage = [UIImage imageWithCGImage:subImageRef];
18. UIGraphicsEndImageContext();
19.
20. return smallImage;
21. }
22.
23. //等比例缩放
24. -(UIImage*)scaleToSize:(CGSize)size
25. {
26. CGFloat width = CGImageGetWidth(self.CGImage);
27. CGFloat height = CGImageGetHeight(self.CGImage);
28.
29. float verticalRadio = size.height*1.0/height;
30. float horizontalRadio = size.width*1.0/width;
31.
32. float radio = 1;
33. if(verticalRadio>1 && horizontalRadio>1)
34. {
35. radio = verticalRadio > horizontalRadio ? horizontalRadio : verticalRadio;
36. }
37. else
38. {
39. radio = verticalRadio < horizontalRadio ? verticalRadio : horizontalRadio;
40. }
41.
42. width = width*radio;
43. height = height*radio;
44.
45. int xPos = (size.width - width)/2;
46. int yPos = (size.height-height)/2;
47.
48. // 创建一个bitmap的context
49. // 并把它设置成为当前正在使用的context
50. UIGraphicsBeginImageContext(size);
51.
52. // 绘制改变大小的图片
53. [self drawInRect:CGRectMake(xPos, yPos, width, height)];
54.
55. // 从当前context中创建一个改变大小后的图片
56. UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();
57.
58. // 使当前的context出堆栈
59. UIGraphicsEndImageContext();
60.
61. // 返回新的改变大小后的图片
62. return scaledImage;
63. }
64. @end
