将图片放大缩小的想要的尺寸

+ (UIImage*)imageWithImage:(UIImage*)image scaledToSize:(CGSize)newSize

{

    UIGraphicsBeginImageContext(newSize);

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

    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return image;

}