ios UIImage修改大小后图片模糊解决办法

这个方法不100%保证能解决，但是大部分修改后依然很清晰

- (UIImage *)scaleToSize:(UIImage *)img size:(CGSize)size{
    UIGraphicsBeginImageContextWithOptions(size, NO, [UIScreen mainScreen].scale);
    [img drawInRect:CGRectMake(0, 0, size.width, size.height)];
    UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return scaledImage;
}