class Image

class Image {
    
    /**
     * Scales image dimensions while maintaining aspect ratio.
     *
     * The resulting dimensions can be smaller for one or both target dimensions.
     *
     * @param array $dimensions
     *   Dimensions to be modified - an array with components width and height, in
     *   pixels.
     * @param int $width
     *   (optional) The target width, in pixels. If this value is NULL then the
     *   scaling will be based only on the height value.
     * @param int $height
     *   (optional) The target height, in pixels. If this value is NULL then the
     *   scaling will be based only on the width value.
     * @param bool $upscale
     *   (optional) Boolean indicating that images smaller than the target
     *   dimensions will be scaled up. This generally results in a low quality
     *   image.
     *
     * @return bool
     *   TRUE if $dimensions was modified, FALSE otherwise.
     */
    public static function scaleDimensions(array &$dimensions, $width = NULL, $height = NULL, $upscale = FALSE) {
        $aspect = $dimensions['height'] / $dimensions['width'];
        // Calculate one of the dimensions from the other target dimension,
        // ensuring the same aspect ratio as the source dimensions. If one of the
        // target dimensions is missing, that is the one that is calculated. If both
        // are specified then the dimension calculated is the one that would not be
        // calculated to be bigger than its target.
        if ($width && !$height || $width && $height && $aspect < $height / $width) {
            $height = (int) round($width * $aspect);
        }
        else {
            $width = (int) round($height / $aspect);
        }
        // Don't upscale if the option isn't enabled.
        if (!$upscale && ($width >= $dimensions['width'] || $height >= $dimensions['height'])) {
            return FALSE;
        }
        $dimensions['width'] = $width;
        $dimensions['height'] = $height;
        return TRUE;
    }

}