详解iOS裁剪圆形图像并显示(类似于微信头像)

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#import 

@interface UIImage (DY)

+ (instancetype)circleOldImage:(UIImage *)originalImage borderWidth:(CGFloat)borderWidth borderColor:(UIColor *)borderColor;

@end

#import "UIImage+DY.h"

@implementation UIImage (DY)

+ (instancetype)circleOldImage:(UIImage *)originalImage borderWidth:(CGFloat)borderWidth borderColor:(UIColor *)borderColor
{
  // 1.加载原图
  UIImage *oldImage = originalImage;

  // 2.开启上下文
  CGFloat imageW = oldImage.size.width + 2 * borderWidth;
  CGFloat imageH = oldImage.size.height + 2 * borderWidth;
  CGSize imageSize = CGSizeMake(imageW, imageH);
  UIGraphicsBeginImageContextWithOptions(imageSize, NO, 0.0);

  // 3.取得当前的上下文
  CGContextRef ctx = UIGraphicsGetCurrentContext();

  // 4.画边框(大圆)
  [borderColor set];
  CGFloat bigRadius = imageW * 0.5; // 大圆半径
  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 - borderWidth;
  CGContextAddArc(ctx, centerX, centerY, smallRadius, 0, M_PI * 2, 0);
  // 裁剪(后面画的东西才会受裁剪的影响)
  CGContextClip(ctx);

  // 6.画图
  [oldImage drawInRect:CGRectMake(borderWidth, borderWidth, oldImage.size.width, oldImage.size.height)];

  // 7.取图
  UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();

  // 8.结束上下文
  UIGraphicsEndImageContext();

  return newImage;
}


@end

#import 
#import "UIImage+DY.h" //加载类别

@interface ViewController : UIViewController //一定要添加这两个Delegate


@property (strong, nonatomic) UIImagePickerController *imagePickerController;

- (IBAction)btnPressed:(id)sender;

@property (strong, nonatomic) IBOutlet UIImageView *ablumImageView;


@end

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
  [super viewDidLoad];
  // Do any additional setup after loading the view, typically from a nib.
}


- (void)didReceiveMemoryWarning {
  [super didReceiveMemoryWarning];
  // Dispose of any resources that can be recreated.
}


- (IBAction)btnPressed:(id)sender {

  if([UIImagePickerController isSourceTypeAvailable: UIImagePickerControllerSourceTypePhotoLibrary]) {

    //首先判断是否支持照片库，这个方法中的参数要和_imagePickerController.sourceType的值保持一致

    //如果支持

    _imagePickerController = [[UIImagePickerController alloc]init];

    _imagePickerController.view.backgroundColor = [UIColor orangeColor];
    _imagePickerController.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
    _imagePickerController.delegate = self;
    _imagePickerController.allowsEditing = YES; //该参数默认是NO，建议设置为YES，否则裁剪成圆形图片的方法将获取到的是椭圆形的图片，与你的预想大相径庭

    [self presentViewController:_imagePickerController animated:YES completion:nil];

  }


}


- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {

  _ablumImageView.image = [UIImage circleOldImage:[info objectForKey:UIImagePickerControllerEditedImage] borderWidth:30.0f borderColor:[UIColor orangeColor]]; 
  //该方法中Info的Key值“UIImagePickerControllerEditedImage”表示的是选择裁剪后的图片，如果使用这个Key值，则_imagePickerController.allowsEditing的值需要设置为YES。

  //如果_imagePickerController.allowsEditing的值设置的NO，则这个Key的值应该设置为UIImagePickerControllerOriginalImage

  /*
  info中的Key的值有如下几个：

  NSString *const UIImagePickerControllerMediaType ;指定用户选择的媒体类型（文章最后进行扩展）
NSString *const UIImagePickerControllerOriginalImage ;原始图片
NSString *const UIImagePickerControllerEditedImage ;修改后的图片
NSString *const UIImagePickerControllerCropRect ;裁剪尺寸
NSString *const UIImagePickerControllerMediaURL ;媒体的URL
NSString *const UIImagePickerControllerReferenceURL ;原件的URL
NSString *const UIImagePickerControllerMediaMetadata;当来数据来源是照相机的时候这个值才有效

  */


  [self dismissViewControllerAnimated:YES completion:nil];

}
- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker{


  [self dismissViewControllerAnimated:YES completion:nil];

}

@end