图片裁剪之圆形头像

 1 + (instancetype)circleImageWithName:(NSString *)name borderWidth:(CGFloat)borderWidth borderColor:(UIColor *)borderColor
 2 {
 3     // 1.加载原图
 4     UIImage *oldImage = [UIImage imageNamed:name];
 5     
 6     // 2.开启上下文
 7     CGFloat imageW = oldImage.size.width + 2 * borderWidth;
 8     CGFloat imageH = oldImage.size.height + 2 * borderWidth;
 9     CGSize imageSize = CGSizeMake(imageW, imageH);
10     UIGraphicsBeginImageContextWithOptions(imageSize, NO, 0.0);
11     
12     // 3.取得当前的上下文
13     CGContextRef ctx = UIGraphicsGetCurrentContext();
14     
15     // 4.画边框(大圆)
16     [borderColor set];
17     CGFloat bigRadius = imageW * 0.5; // 大圆半径
18     CGFloat centerX = bigRadius; // 圆心
19     CGFloat centerY = bigRadius;
20     CGContextAddArc(ctx, centerX, centerY, bigRadius, 0, M_PI * 2, 0);
21     CGContextFillPath(ctx); // 画圆
22     
23     // 5.小圆
24     CGFloat smallRadius = bigRadius - borderWidth;
25     CGContextAddArc(ctx, centerX, centerY, smallRadius, 0, M_PI * 2, 0);
26     // 裁剪(后面画的东西才会受裁剪的影响)
27     CGContextClip(ctx);
28     
29     // 6.画图
30     [oldImage drawInRect:CGRectMake(borderWidth, borderWidth, oldImage.size.width, oldImage.size.height)];
31     
32     // 7.取图
33     UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
34     
35     // 8.结束上下文
36     UIGraphicsEndImageContext();
37     
38     return newImage;
39 }