Wordpress , display resized image in theme with PHP

Question

I'm coding a shortcode that accept one media ID as an attribute. This shortcode should then display the image at an existing size registered with add_image_size. Problem : my image is not displayed at the correct size.

Explanations :

• My media image has been uploaded in the WP library. The original file size is huge (1227x924). The media has the ID 294.

• I registered an image size in functions.php :

  function my_after_setup_theme(){  
      add_image_size('my-image-size', 210, 136, true);  
  }  
  add_action('after_setup_theme', 'my_after_setup_theme');
  

• I insert my shortcode in one of my pages : [my_shortcode imageid="294"]

• My shortcode code is :

  function my_shortcode_func($atts)
  {
      $a = shortcode_atts(array(
          'imageid'    => 0,
      ), $atts);
      if ($a['imageid'] == 0) {
          // default placeholder image
          $img = 'img src="http://placehold.it/210x136"/>';
      } else {
          // get resized  (NOT WORKING !)
          $img = wp_get_attachment_image($a['imageid'], 'my-image-size');
      }
      return $img;
  }
  add_shortcode('my_shortcode', 'my_shortcode_func');
  

• I expect the original image to be resized at the correct size (ie : 210x136) in a new thumbnail file. Instead, the $img displays the original image (1227x924) , displayed at an intermediate size via the width and height attributes of the HTML <img> tag :

What am I doing wrong ?

thanks for help.

Answer 1

Did you register the thumbnail size after uploading the media? If so, you will need to use a plugin to regenerate the thumbnails.

Additionally, I don't believe you need to wrap thumbnail size declarations as you have done, I have the following;

if (function_exists('add_theme_support'))
{
   add_theme_support('post-thumbnails'); // Featured image support for posts - you may not need this bit.
   add_image_size('large', 700, '', true); // Large Thumbnail - This is the bit you would need
} 

So it would be worth checking if your thumbnails are actually be generated to start with, as I have never done it the way you have defined in your question.