UIImage 调整图片大小

-(UIImage *)scaleToSize:(UIImage *)img size:(CGSize)size

{

    UIGraphicsBeginImageContext(size);

    [img drawInRect:CGRectMake(0, 0, size.width, size.height)];

    UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return scaledImage;

}