Any way to manually generate a transform on an asset source? I imported all of the posts from a WordPress blog, using a regular expression to update the image URLs to their new location in a Craft Asset Source. However, many of the original photos are straight out of the camera - 2000x3000px or whatever. What I would like to do is use that same regex to update them to a transformed version: so /wp-content/uploads/2014/12/photo.jpg would become /media/blog/_fullWidth/photo.jpg. I already set up that replacement and it's working great. 

The problem is that the "Full Width" transform hasn't been generated, and just calling the URL from a Rich Text field bypasses Craft, so it never gets generated. Short of manually re-adding every photo through Redactor with the transform, is there any way to force Craft to generate a particular transform on all the images in an asset source?
You could just make a temporary template that makes Craft generate them for you. And depending on how many these are, you better use limit and offset with your craft.assets call.

{% set images = craft.assets.source('myAssetSource').limit(50).offset(0) %}
{% for image in images %}
    &lt;img src="{{ image.url('fullwidth') }}"&gt;
{% endfor %}