O UIImage sempre fica indistinto quando é dimensionado. O que posso fazer se ele manter a clareza?

<code>- (UIImage *)rescaleImageToSize:(CGSize)size {
    CGRect rect = CGRectMake(0.0, 0.0, size.width, size.height);
    UIGraphicsBeginImageContext(rect.size);
    [self drawInRect:rect];  // scales image to rect
    UIImage *resImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return resImage;
}
</code>