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I've created a new custom post type and I need the post thumbnails or featured images generated by the get_the_post_thumbnail() function to be set in percent, rather than pixels, as I'm using a fluid grid. Ideally I would only set the width (to 100%). Is there a way to do this? Potentially using add_image_size()?

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up vote 8 down vote accepted

have you tried,

if(has_post_thumbnail()) {                    
    $image_src = wp_get_attachment_image_src( get_post_thumbnail_id(),'full' );
     echo '<img src="' . $image_src[0]  . '" width="100%"  />';
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Smart +1. Should be plugin ;) – kaiser Jun 27 '11 at 1:25
Perfect! Thanks! – daysrunaway Jul 1 '11 at 5:41

It's not possible to change the units of the default width and height output, but you can possibly override the output via css:

/* these are the classes that get added per default */

Then you can override it via something like body img.attachment-large { width: 50% !important; height: 50% !important; }

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I've solved that issue getting rid of all width and height attributes set by WP:

    //tidy up img tags. We don't want inline height and width added by WP.
    //we'd rather use media queries and fluid img.
        function remove_image_dim_attr($html) {
            $html=preg_replace( '/width=(["\'])(.*?)\1/', '', $html );
            $html=preg_replace( '/height=(["\'])(.*?)\1/', '', $html );
            return $html;
        add_filter( 'get_image_tag','remove_image_dim_attr' );
        add_filter( 'image_send_to_editor','remove_image_dim_attr' );
        add_filter( 'post_thumbnail_html','remove_image_dim_attr' );
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