1 裁剪图片
- (UIImage *)croppedImage:(UIImage *)image
 {

     if (image)

     {

         float min = MIN(image.size.width,image.size.height);

         CGRect rectMAX = CGRectMake((image.size.width-min)/2, (image.size.height-min)/2, min, min);

         

         CGImageRef subImageRef = CGImageCreateWithImageInRect(image.CGImage, rectMAX);

         

         UIGraphicsBeginImageContext(rectMAX.size);

         CGContextRef context = UIGraphicsGetCurrentContext();

         CGContextDrawImage(context, CGRectMake(0, 0, min, min), subImageRef);

         UIImage *viewImage = [UIImage imageWithCGImage:subImageRef];

         UIGraphicsEndImageContext();

         CGImageRelease(subImageRef);

         return viewImage;

     }

     

     return nil;

}

2绘制背景色
    CGContextRef context = UIGraphicsGetCurrentContext(); 
     UIColor *bgColor = [UIColor colorWithRed:220/255.0 green:220/255.0 blue:220/255.0 alpha:1.0];
     CGContextSetStrokeColorWithColor(context, bgColor.CGColor);
     CGContextSetFillColorWithColor(context, bgColor.CGColor);
     CGRect bgRect = CGRectMake(0, kUserAlbumWidth, self.frame.size.width, kThumbWidth);
     CGContextAddRect(context, bgRect);
     CGContextDrawPath(context, kCGPathFillStroke);