cropResize not working

I'm having trouble with using cropResize in a simple gallery. I'm basically replicating the simple gallery recipe from the cookbook, but cropResize() is breaking and I'm not getting any useful information from the debug bar or using twig dump(). This is my twig:
<section>
<ul>
{% for image in page.media.images %}
<li>
{{ image.html() }} <!-- this works -->
{{ image.cropResize(300,300).html() }} <!-- this doesn't work ? -->
</li>
{% endfor %}
</ul>
</section>

I have images in the folder with the gallery template, etc. not sure what else I should look at? Thanks

Do you get any error message? Are errors.display and debugger.enabled enabled in system.yaml?

yes, both of those are enabled. I'm not getting any messages.

Check to make sure you have gd installed for PHP. That is required for image manipulation to function.

yep, I have gd installed and enabled.

My next step is to deploy my test site on a vagrant vm and see if the issue is specific to my MAMP stack or not.

Another thing it could be is a missing JPG or PNG library. that GD relies on?

http://stackoverflow.com/questions/25124761/no-png-support-in-php-gd-library-but-has-gif-and-jpeg-support-how-can-i-fix-thi

BTW I use homebrew to install PHP on my mac, and it works just fine: http://getgrav.org/blog/mac-os-x-apache-setup-multiple-php-versions

thanks for the stackoverflow link. I checked those libraries too. so far everything looks like it should work. I'm using bitnami's mampstack because I was trying to avoid the native installs on Mac and I've found bitnami's lamp and wamp stacks to be decent for development. But I'm going to try it on a vagrant linux box and see what happens.

ok, I made some progress on it. I changed the template for the 01.home page and the call works there. i had it nested several modules deep originally. so it's probably an issue with nesting page modules.

That might be a routing issue then. Does the page actually show up? If so then routing is working, but could be a pathing issue on image specifically.

the page shows up, but the folder paths were probably too long. I'm playing around with that to see if I can work around it.