Quartz2D 製做圓形圖片(頭像)

//1.加載原圖
    UIImage *oldImage = [UIImage imageNamed:@"girl"];
    
    //2.開啓上下文
    UIGraphicsBeginImageContextWithOptions(oldImage.size, NO, 0.0);
    
    //3.取得當前的上下文
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    
    //4.畫圓
    CGRect circleRect = CGRectMake(0, 0, oldImage.size.width, oldImage.size.height);
    CGContextAddEllipseInRect(ctx, circleRect);
    
    //5.裁剪(按照當前的路徑形狀裁剪)
    CGContextClip(ctx);
    
    //6.畫圖
    [oldImage drawInRect:circleRect];
    
    //7.取圖
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    
    //8.結束
    UIGraphicsEndImageContext();
    
    //9.寫出文件
    NSData *data = UIImagePNGRepresentation(newImage);
    NSString *path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) firstObject];
    NSString *realpath = [path stringByAppendingPathComponent:@"new.png"];
    [data writeToFile:realpath atomically:YES];
    //打印一下圖片的沙盒路徑
    NSLog(@"%@",realpath);