如何在NSAttributedString中设置边距（填充）？

Question

我使用NSAttributedString将图像插入到UITextView中，但问题是我想将顶部填充设置为几个点（2/3），以便图像y中心位于{{3文本。

这是我的代码：

        NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithString:currentMessage];
NSTextAttachment *textAttachment = [[NSTextAttachment alloc] init];
        textAttachment.image = [UIImage imageWithCGImage:[[imagesArray objectAtIndex:count] CGImage] scale:4.0 orientation:UIImageOrientationUp];
        NSAttributedString *attrStringWithImage = [NSAttributedString attributedStringWithAttachment:textAttachment];

        int newPos = [[imagesPosArray objectAtIndex:count] intValue];
        [attributedString replaceCharactersInRange:NSMakeRange(newPos, 1) withAttributedString:attrStringWithImage];
        messageTextView.attributedText = attributedString;