So when I finished up with my twentyeleven child theme, I had an even wider header image than my previous child theme. A while ago we covered how to include featured or attached images in our RSS feed. Well, that technique works great, but it uses the default image size of your theme, whatever that is defined as. With a 1050x175px header image, that looked a bit silly in my feed. So I just adjusted the featured image size by including a specific image for my feed. Check this out!

Including images in your RSS feed can be done from functions.php of course. However this is one of those features that doesn’t seem to be theme specific to me. So I keep this code in my functionality plugin. I definitely recommend you consider doing the same. A functionality plugin is so much better than adding everything to functions.php. Any time I add a feature or option which I’m going to always want to be on VoodooPress, regardless of theme, I add it to my plugin. My own little custom widgets, and various other things, like images in my RSS feed.

So here was the code we originally had from that past tutorial:

// THIS INCLUDES THE THUMBNAIL IN OUR RSS FEED
add_filter( 'the_excerpt_rss', 'voodoo_insertThumbnailRSS' );
add_filter( 'the_content_feed', 'voodoo_insertThumbnailRSS' );
function voodoo_insertThumbnailRSS( $content ) {

	global $post;

	if ( has_post_thumbnail( $post->ID ) )
		$content = '' . get_the_post_thumbnail( $post->ID, 'thumbnail' ) . '' . $content;

	return $content;
}

So that absolutely works. Your default thumbnail size will be used in your RSS feed. But depending on what size your featured image is, it may or may not look good. And it can change from theme to theme. So let’s fix that and get a nice, consistent rss feed image!

// THIS INCLUDES THE THUMBNAIL IN OUR RSS FEED
add_filter( 'the_excerpt_rss', 'voodoo_insertThumbnailRSS' );
add_filter( 'the_content_feed', 'voodoo_insertThumbnailRSS' );
add_image_size ( 'rss-thumb', 600, 150, true );
function voodoo_insertThumbnailRSS( $content ) {
	
	global $post;
	
	if ( has_post_thumbnail( $post->ID ) )
		$content = '' . get_the_post_thumbnail( $post->ID, 'rss-thumb' ) . '' . $content;
	
	return $content;
}

Do you see what we changed there? It’s pretty simple, on line 4 we register a specific size of image to use just for our rss feed. Mine is 600x150px. That seems like a really good size for an rss feed image. It looks great in my feed, but of course, pick what works best for you! Now after we register that size, we call it in line 10. Basically whatever you name your image in line 4 with the add_image_size, you must call in line 10. Simple right? Just one of those things I hadn’t thought of doing before.

Of course for this to work, your theme needs to support featured/thumbnail images. If you are working with a child theme for twentyeleven, or twentyten, they are supported. Otherwise you would need to add that support to your theme. There is no reason any theme out there should not support the featured image, it’s been around since version 2.9. You could add a check in your code, to ensure thumbnails are supported before trying to register the size. I no longer do that, as I never intend to use a theme without them active.