文字横に画像

試行錯誤の結果次のようになった。

+ (NSAttributedString *)backSymbol {
    
    UIImage *image = [UIImage imageNamed:@"backbutton"];
    NSTextAttachment *attachment = [[NSTextAttachment alloc] init];
    attachment.image = image;
    NSMutableAttributedString *ret = [[NSMutableAttributedString alloc] init];
    
    UIFont *font = [UIFont systemFontOfSize:17.0];
    CGSize size = CGSizeMake(font.lineHeight * image.size.width/image.size.height, font.lineHeight);
    
    CGFloat y = round(font.capHeight - size.height)/2;
    [attachment setBounds:CGRectMake(-size.width*1/4, y, size.width, size.height)];
    
    
    
    NSAttributedString *back = [NSMutableAttributedString attributedStringWithAttachment:attachment];
    
    [ret appendAttributedString:back];
//    NSMutableAttributedString *back = [[NSMutableAttributedString alloc] initWithString:@"＜"];
    [ret addAttribute:NSFontAttributeName
                 value:[UIFont boldSystemFontOfSize:21.0]
                 range:NSMakeRange(0,back.length)];
    return ret;
}

参考

Swift5 UILabelに画像(UIImage)を表示する NSAttributedString NSTextAttachment - Qiita

A-Liaison BLOG: iOSのフォントのお話