ObjectiveC 图片压缩

- (NSData *)resizeWithImage:(UIImage*)image scale:(CGFloat)scale compression:(CGFloat)compression
{
    CGSize newSize = CGSizeMake(image.size.width * scale, image.size.height * scale);
    
    UIGraphicsBeginImageContext(newSize);
    [image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
    UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    return UIImageJPEGRepresentation(newImage, compression);
}