［自定义组件之四］利用Quartz2D实现圆形图片显示

布满荆棘的人生 2022-08-20 13:10 105阅读 0赞

#import "ViewController.h"
    
    @interface ViewController ()
    
    @end
    
    @implementation ViewController
    
    -(UIImage*)CircleImg
    {
        /*添加图片*/
        UIImage* img = [UIImage imageNamed:@"J罗.jpg"];
        CGFloat borderWith = 20.0f;
        CGSize imgSize = CGSizeMake(img.size.width + borderWith, img.size.height + borderWith);
        CGFloat bigRadius = imgSize.width * 0.5;/*外圆半径*/
        CGFloat smallRadius = bigRadius - borderWith;/*内圆半径*/
        
        UIGraphicsBeginImageContextWithOptions(imgSize, NO, 0.0f);
        CGContextRef ctx = UIGraphicsGetCurrentContext();/*得到图片的上下文*/
        CGContextAddArc(ctx, bigRadius, bigRadius, bigRadius - borderWith / 2, 0, M_PI * 2, 0);/*添加大圆*/
        CGContextSetStrokeColorWithColor(ctx, [[UIColor redColor] CGColor]);
        CGContextSetLineWidth(ctx, borderWith);/*设置线宽*/
        CGContextStrokePath(ctx);/*画大圆*/
        
        CGContextAddArc(ctx, bigRadius, bigRadius, smallRadius, 0, M_PI * 2, 0);/*添加小圆*/
        CGContextClip(ctx);/*剪裁，后面的受影响*/
        CGRect rect = CGRectMake(borderWith, borderWith, img.size.width, img.size.height);
        [img drawInRect: rect];/*画图*/
        UIImage* img2 = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        return img2;
    }
    
    - (void)viewDidLoad {
        [super viewDidLoad];
        /*用的是实际尺寸370，要不画出的border也会缩放*/
        UIImageView* imgView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 20, 370, 370)];
        imgView.image = [self CircleImg];
        [self.view addSubview:imgView];
    }
    
    - (void)didReceiveMemoryWarning {
        [super didReceiveMemoryWarning];
        // Dispose of any resources that can be recreated.
    }
    
    @end

说是这个方法可扩展性高，比如添加个边框之类的。

注意大圆的半径，要减去边框的一半，否则边框显示不全。

参考：http://www.360doc.com/content/15/0128/17/20918780\_444509231.shtml