问将照片调整为像Flickr和Facebook photostreams那样的缩略图方块？

EN

CGFloat horizontalRatio = newSize.width/oldSize.width;
CGFloat verticalRatio = newSize.height/oldSize.height;
CGFloat ratio = MAX(horizontalRatio, verticalRatio);
CGSize newSize = CGSizeMake(oldSize.width *ratio, newSize.height*ratio)

UIGraphicsBeginImageContextWithOptions(newSize, YES, 0);
    [self drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

        CGRect cropRect = CGRectMake ((newImage.size.width - width) / 2, (newImage.size.height - height) / 2, width, height)
        UIGraphicsBeginImageContextWithOptions(cropRect.size, YES, 0); 
        CGContextRef context = UIGraphicsGetCurrentContext();
        CGRect drawRect = CGRectMake(-cropRect.origin.x, -cropRect.origin.y, self.size.width, self.size.height);
        CGContextClipToRect(context, CGRectMake(0, 0, cropRect.size.width, cropRect.size.height));
        [self drawInRect:drawRect];
        UIImage* croppedImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
return croppedImage;