iOS - Image缩小不变形模糊

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

    UIGraphicsBeginImageContextWithOptions(size, NO, [UIScreen mainScreen].scale);

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

    UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    returnscaledImage;

}

关键在于 [UIScreen mainScreen].scale