Sometimes if you view source using certain browsers (firefox, chrome), it omits the /> tag. Try view source using a notepad or something, it should display proper /> tag.
If you want a shorter tag, use this:
<?php echo img(array('src'=>'image/picture.jpg', 'alt'=> 'alt information')); ?>
Here is detailed information:
https://codeigniter.com/user_guide/helpers/html_helper.html#img
More examples:
<img src="<?php echo base_url('assets/uploads/' . $gambar)?>" alt=""/>
and
<img src='<?php echo base_url("assets/uploads/$gambar")?>' alt=""/>
Note: Unlike the double-quoted and heredoc syntaxes, variables and escape sequences for special characters will not be expanded when they occur in single quoted strings.