Drupal 7 : create your own image effect for use in image styles

Mathieu — Wed, 25 Feb 2015 18:56:00 +0100

Drupal comes with many predefined effects, you can combine them in image styles to get the picture you want. But what if you have to make your own effect ? Here is how.

Step 1 : create a module

If you are a drupal developer, you should know how to make a module. Okay, I am lazy too :

myeffect.info :

name = My Effect
description = "My wonderful border effect"
core = 7.x
dependencies[] = image
files[] = myeffect.module
package = Media

Step 2 : declare your effect

Implement hook_image_effect_info :

function myeffect_image_effect_info() {
  $effects = array(
    'myeffect_image_border' => array(
      'label' => t('My Effect - Border'),
      'help' => t('Add border to an image'),
      'effect callback' => '_myeffect_image_border_effect',
// Let's make things simpler...
//      'form callback' => '_myeffect_image_border_form',
//      'summary theme' => '_myeffect_image_border_summary',
    ),
  );
  return $effects;
}

Step 3 : write the callback

function _myeffect_image_border_effect(&$image, $data) {
  if (!_myeffect_image_border($image, $data)) {
    watchdog('image', 'Image add border failed using the %toolkit toolkit on %path (%mimetype)', array(
      '%toolkit' => $image->toolkit,
      '%path' => $image->source,
      '%mimetype' => $image->info['mime_type'],
    ), WATCHDOG_ERROR);
    return FALSE;
  }
  return TRUE;
}

function _myeffect_image_border(stdClass $image, $data) {
  if ($image->toolkit == 'gd') {
    $params = array($image, $data);
    return call_user_func_array('_myeffect_gd_border', $params);
  } else {
    watchdog('image', 'The selected image handling toolkit %toolkit can not correctly process %function.', array(
      '%toolkit' => $image->toolkit,
      '%function' => $function,
    ), WATCHDOG_ERROR);
    return FALSE;
  }
}

Step 4 : make your effect !

function _myeffect_gd_border(stdClass $image, $data) {

  $width = $image->info['width'];
  $height = $image->info['height'];

  // Note : source image is in $image->resource
  $dst = imagecreatetruecolor($width, $height);

...

  // Update image object.
  $image->resource = $dst;
  $image->info['width'] = $width;
  $image->info['height'] = $height;

  return TRUE;
}

Source