iOS 利用Context裁剪图片

下面的代码可以裁剪出圆形的图片，

1，先把不规则图片转成正方形图片

UIGraphicsBeginImageContext(newSize);
   
 [image drawInRect:CGRectMake(0,0,newSize.width,newSize.width)];

 UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();

 UIGraphicsEndImageContext();

2 ，把正方形图像绘制剪切为圆形

 UIGraphicsBeginImageContext(image.size);
 CGContextRef context = UIGraphicsGetCurrentContext();

    
 CGRect rect = CGRectMake(0, 0, image.size.width, image.size.height);
 CGContextAddEllipseInRect(context, rect);
 CGContextClip(context); //进行剪切，所有context绘制只保留能够被当前path进行fill的区域
 [image drawInRect:rect]; //绘制原图
   
    
 UIImage *newimg = UIGraphicsGetImageFromCurrentImageContext();
 UIGraphicsEndImageContext();