Method execute

/**
 * Method to apply a background color to an image resource.
 *
 * @param   array  $options  An array of options for the filter.
 *                           color  Background matte color
 *
 * @return  void
 *
 * @since   3.4
 * @throws  \InvalidArgumentException
 */
public function execute(array $options = [])
{
    // Validate that the color value exists and is an integer.
    if (!isset($options['color'])) {
        throw new \InvalidArgumentException('No color value was given. Expected string or array.');
    }
    $colorCode = $options['color'] ?? null;
    // Get resource dimensions
    $width = imagesx($this->handle);
    $height = imagesy($this->handle);
    // Sanitize color
    $rgba = $this->sanitizeColor($colorCode);
    // Enforce alpha on source image
    if (imageistruecolor($this->handle)) {
        imagealphablending($this->handle, false);
        imagesavealpha($this->handle, true);
    }
    // Create background
    $bg = imagecreatetruecolor($width, $height);
    imagesavealpha($bg, empty($rgba['alpha']));
    // Allocate background color.
    $color = imagecolorallocatealpha($bg, $rgba['red'], $rgba['green'], $rgba['blue'], $rgba['alpha']);
    // Fill background
    imagefill($bg, 0, 0, $color);
    // Apply image over background
    imagecopy($bg, $this->handle, 0, 0, 0, 0, $width, $height);
    // Move flattened result onto current handle.
    // If handle was palette-based, it'll stay like that.
    imagecopy($this->handle, $bg, 0, 0, 0, 0, $width, $height);
    // Free up memory
    imagedestroy($bg);
}