class Crop

class Crop extends GDImageToolkitOperationBase {
    
    /**
     * {@inheritdoc}
     */
    protected function arguments() {
        return [
            'x' => [
                'description' => 'The starting x offset at which to start the crop, in pixels',
            ],
            'y' => [
                'description' => 'The starting y offset at which to start the crop, in pixels',
            ],
            'width' => [
                'description' => 'The width of the cropped area, in pixels',
                'required' => FALSE,
                'default' => NULL,
            ],
            'height' => [
                'description' => 'The height of the cropped area, in pixels',
                'required' => FALSE,
                'default' => NULL,
            ],
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    protected function validateArguments(array $arguments) {
        // Assure at least one dimension.
        if (empty($arguments['width']) && empty($arguments['height'])) {
            throw new \InvalidArgumentException("At least one dimension ('width' or 'height') must be provided to the image 'crop' operation");
        }
        // Preserve aspect.
        $aspect = $this->getToolkit()
            ->getHeight() / $this->getToolkit()
            ->getWidth();
        $arguments['height'] = empty($arguments['height']) ? $arguments['width'] * $aspect : $arguments['height'];
        $arguments['width'] = empty($arguments['width']) ? $arguments['height'] / $aspect : $arguments['width'];
        // Assure integers for all arguments.
        foreach ([
            'x',
            'y',
            'width',
            'height',
        ] as $key) {
            $arguments[$key] = (int) round($arguments[$key]);
        }
        // Fail when width or height are 0 or negative.
        if ($arguments['width'] <= 0) {
            throw new \InvalidArgumentException("Invalid width ('{$arguments['width']}') specified for the image 'crop' operation");
        }
        if ($arguments['height'] <= 0) {
            throw new \InvalidArgumentException("Invalid height ('{$arguments['height']}') specified for the image 'crop' operation");
        }
        return $arguments;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function execute(array $arguments) {
        // Create a new resource of the required dimensions, and copy and resize
        // the original resource on it with resampling. Destroy the original
        // resource upon success.
        $original_resource = $this->getToolkit()
            ->getResource();
        $data = [
            'width' => $arguments['width'],
            'height' => $arguments['height'],
            'extension' => image_type_to_extension($this->getToolkit()
                ->getType(), FALSE),
            'transparent_color' => $this->getToolkit()
                ->getTransparentColor(),
            'is_temp' => TRUE,
        ];
        if ($this->getToolkit()
            ->apply('create_new', $data)) {
            if (imagecopyresampled($this->getToolkit()
                ->getResource(), $original_resource, 0, 0, $arguments['x'], $arguments['y'], $arguments['width'], $arguments['height'], $arguments['width'], $arguments['height'])) {
                imagedestroy($original_resource);
                return TRUE;
            }
            else {
                // In case of failure, destroy the temporary resource and restore
                // the original one.
                imagedestroy($this->getToolkit()
                    ->getResource());
                $this->getToolkit()
                    ->setResource($original_resource);
            }
        }
        return FALSE;
    }

}