Symfony2 - Checking if a file exists in Twig - image

Question

Is there a way to check if the file exists in Twig for an image uploaded in a newly created post?
The way I have my post setup is if an image is not uploaded the Twig template will show an empty box with the proportions of where the image should be, but it's a blank box that's awkward to look at.
Question, is if there is a specific command to use with an if statement to check if a file exists if so, display the image code if not do not display the image code.
Image code: (this is the code I want to hide if no image exists to get rid of the empty box)
<div class="entry-thumbnail">
<img width="230" height="172" src="{{ asset(['images/', post.image]|join) }}" class="" alt=""/>
</div>

Answer 1

you could write a twig extension and use some code like this:
use Symfony\Component\Filesystem\Filesystem;
use Symfony\Component\Filesystem\Exception\IOException;
use Symfony\Component\Finder\Finder;
$this->fs=new Filesystem();
if (!$this->fs->exists($directory)) {
$this->logger->info("there is no ".$directory." ...");
} else {
$this->logger->info("Directory ".$directory." already exists.");
}
but i would rather use javascripz like
in your img tag :
<img ... onError="this.src='imagefound.gif';" />
update:
The image Tag has an onError-Handler that triggers when the image in the src attribute is not found. So instead of using this simple inline syntax you could do the same like :
pseudo jquery code:
$(document).on('error','img',function(){
$(this).attr("src","../path/to/placeholerImage.png");
});