class UriDependentTestImageEffect

class UriDependentTestImageEffect extends ImageEffectBase {
    
    /**
     * {@inheritdoc}
     */
    public function transformDimensions(array &$dimensions, $uri) {
        $dimensions = $this->getUriDependentDimensions($uri);
    }
    
    /**
     * {@inheritdoc}
     */
    public function applyEffect(ImageInterface $image) {
        $dimensions = $this->getUriDependentDimensions($image->getSource());
        return $image->resize($dimensions['width'], $dimensions['height']);
    }
    
    /**
     * Make the image dimensions dependent on the image file extension.
     *
     * @param string $uri
     *   Original image file URI.
     *
     * @return array
     *   Associative array.
     *   - width: Integer with the derivative image width.
     *   - height: Integer with the derivative image height.
     */
    protected function getUriDependentDimensions($uri) {
        $dimensions = [];
        $extension = pathinfo($uri, PATHINFO_EXTENSION);
        switch (strtolower($extension)) {
            case 'png':
                $dimensions['width'] = $dimensions['height'] = 100;
                break;
            case 'gif':
                $dimensions['width'] = $dimensions['height'] = 50;
                break;
            default:
                $dimensions['width'] = $dimensions['height'] = 20;
                break;
        }
        return $dimensions;
    }

}