UIImage 缩放

- (UIImage*)imageWithImage:(UIImage*)image
              scaledToSize:(CGSize)newSize
{
    UIGraphicsBeginImageContext( newSize );
    [image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
    UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    return newImage;
}