Display thumbnail only if requested size exists

7 comments

1. Assuming the question is about wp_get_attachment_image_src.
   _{It could be also about wp_get_attachment_link, but, although related, this analysis doesn’t includes it.}

   ---

   Got aware of this issue answering this question: How can I view all WP generated thumbnails in Media Manager?.
   _{Refer to it to see a working code regarding the issue on this Question.}

   And it lead to this WordPress forum topic.

   ---

   The function wp_get_attachment_image_src( $attachment_id, $size, $icon ) returns an array containing:

   [0] => url  
   [1] => width  
   [2] => height  
   [3] => is intermediate
   

   If [3] is false, the original image data is returned.

   ---

   Both wp_get_attachment_image_src and wp_get_attachment_link rely in the function image_downsize, inside /wp-includes/media.php.
   And that’s where this 4 items array is being returned.

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2. I’m Not sure about this but i know you can use php’s getimagesize() function
   something like this:

   //This must be in one loop
   
   if(has_post_thumbnail()) {
       $wanted_width = 300;
       $wanted_height = 150;
       $id = get_post_thumbnail_id()
       $image = wp_get_attachment_image_src($id);
       if ($image){
           list($width, $height) = getimagesize($image[0]);
           if (($wanted_height = $width) && ($wanted_height = $height)){
               the_post_thumbnail();
           }
           else{
               //default when no image
               echo '<img src="'.get_bloginfo("template_url").'/images/img-default.png" />';
           }
       }
       else{
           //default when no image
           echo '<img src="'.get_bloginfo("template_url").'/images/img-default.png" />';
       }
   } else {
       //default when no image
       echo '<img src="'.get_bloginfo("template_url").'/images/img-default.png" />';
   }
   

   and i know it’s not an answer to the question directly but you can use a plugin called AJAX Thumbnail Rebuild –
   This plugin allows you to re-build the post thumbnails. Useful if you add_image_size() after already having uploaded post thumbnails.

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3. This is how I was able to display a thumbnail only if a requested size exists:

   if ( has_post_thumbnail() )  {
       $imgdata = wp_get_attachment_image_src( get_post_thumbnail_id(), 'thumbnail' ); //change thumbnail to whatever size you are using
       $imgwidth = $imgdata[1]; // thumbnail's width                   
       $wanted_width = 300; //change this to your liking
       if ( ($imgwidth < $wanted_width ) ) {
           the_post_thumbnail();
       } else { 
           //do whatever you want
       }
   }
   

   To learn more about wp_get_attachment_image_src read the Codex.

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4. There’s a plugin that will actually create the image size automatically for you if it doesn’t exist. http://austinmatzko.com/wordpress-plugins/filosofo-custom-image-sizes/

   I haven’t needed to use this plugin yet myself. But it’s worth a shot. There is talk about adding similar functionality to WP core, maybe in 3.2 http://core.trac.wordpress.org/ticket/15311

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5. It’s seem’s to be a better way.
   Use the global variable $_wp_additional_image_sizes, it’s store all registered image_size.
   So if you want to check if an image size name is define :

     global $_wp_additional_image_sizes;
     if ( array_key_exists( 'desired-image-size' , $_wp_additional_image_sizes) )
     {
       //your code here
     }
     else
     {
       //default code here 
     }
   

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6. The best approach is to use WordPress’ built-in “get_intermediate_image_sizes” function to return the full list of image sizes as an array then look through that.

   show_image_by_size( 10470, 'custom_size' );
   
   function show_image_by_size( $_post_id, $_desired_size ) {
     $_sizes = get_intermediate_image_sizes();
     $_thumbnail_id = get_post_thumbnail_id( $_post_id );
     $_image_size = ( in_array( $_desired_size , $_sizes ) ) ? $_desired_size : 'full';
     $image = wp_get_attachment_image_src( $_thumbnail_id, $_image_size );
     echo '<img src="' . esc_url( $image[0] ) . '" />';
   }
   

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7. Maybe this will help

   <?php 
   //This must be in a loop
   if(has_post_thumbnail()) {
       the_post_thumbnail();
   } else {
       echo '<img src="'.get_bloginfo("template_url").'/images/img-default.png" />';
   }
   ?>
   

   from: http://codex.wordpress.org/Function_Reference/has_post_thumbnail
   I use something like this to check if the image size exists:

   if (function_exists('has_post_thumbnail') && has_post_thumbnail('medium')) {
   //// code to display thumbnail goes here
   }
   else {
   /// otherwise do this
   }
   

   Hope it helps get you going.

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