perch_filter_alt_text_fallback.php

/* GROUP ALT TEXT FALLBACK
=================================================== */
class PerchTemplateFilter_alt_text_fallback extends PerchTemplateFilter 
{
    /* Notes...
        - If no alt text is filled in, use the file name as a fallback so it's not blank
        - e.g. alt="<perch:if exists="alt"><perch:content type="text" id="alt"/><perch:else /><perch:content id="image" filter="convert-filename-to-alt-text"/></perch:if>"
    */
    public function filterBeforeProcessing($value, $valueIsMarkup = false)
    {
        $value = preg_replace(
            array('/-[1-9][.].*/','/[.].*/'),
            array('',''),
            $value
        );

        $value = str_replace(
            array('/perch/resources/', '-'),
            array('', ' '),
            $value
        );

        return ucfirst($value);
    }
}
PerchSystem::register_template_filter('alt-text-fallback', 'PerchTemplateFilter_alt_text_fallback');

Handy if you tend to use descriptive text for your file names, this saves you some work adding alternative text for all your images. Drop this in filters.php.

See Perch's Filter documentation for more information.