图片裁剪

#import "ViewController.h"
#import "UIImage+ZR.h"

@interface ViewController ()

@property (weak, nonatomic) IBOutlet UIImageView *iconV;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    
    UIImage *newImage = [UIImage circleImage:@"me" borderWith:3 borderColor:[UIColor greenColor]];
    self.iconV.image = newImage;
    
}

@end

#import <UIKit/UIKit.h>

@interface UIImage (ZR)

+(instancetype)circleImage:(NSString *)name borderWith:(CGFloat)borderWith borderColor:(UIColor *)borderColor;

@end

#import "UIImage+ZR.h"

@implementation UIImage (ZR)

+(instancetype)circleImage:(NSString *)name borderWith:(CGFloat)borderWith borderColor:(UIColor *)borderColor{
    
    UIImage *oldImage = [UIImage imageNamed:name];
    //2.开启上下文
    CGFloat imageW = oldImage.size.width + 2*borderWith;
    CGFloat imageH = oldImage.size.height + 2*borderWith;
    CGSize imageSize = CGSizeMake(imageH, imageW);
    
    UIGraphicsBeginImageContextWithOptions(imageSize, NO, 0.0);
    
    //3.取得当前上下文
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    //4.画圆边框（大圆）
    [borderColor set];
    CGFloat bigRadius = imageW * 0.5;//半径
    CGFloat centerX = bigRadius;//圆心
    CGFloat centerY = bigRadius;
    CGContextAddArc(ctx, centerX, centerY, bigRadius, 0, M_PI * 2, 0);
    CGContextFillPath(ctx);//画圆
    
    //5.小圆
    CGFloat smallRadius = bigRadius - borderWith;
    CGContextAddArc(ctx, centerX, centerY, smallRadius, 0, M_PI *2, 0);
    //裁剪(后面画的东西才会受影响)
    CGContextClip(ctx);
    //6.画图
    [oldImage drawInRect:CGRectMake(borderWith, borderWith, oldImage.size.width, oldImage.size.height)];
    
    //7.取图
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    //8.结束上下文
    UIGraphicsEndImageContext();
    
    return newImage;
}

@end