Craft\ImagerService::__construct PHP Method

    public function __construct()
    {
        $extension = mb_strtolower(craft()->config->get('imageDriver'));
        if ($extension === 'gd') {
            // set in config
            $this->imageDriver = 'gd';
        } else {
            if ($extension === 'imagick') {
                $this->imageDriver = 'imagick';
            } else {
                // autodetect
                if (craft()->images->isGd()) {
                    $this->imageDriver = 'gd';
                } else {
                    $this->imageDriver = 'imagick';
                }
            }
        }
        $this->imagineInstance = $this->_createImagineInstance();
        if ($this->imageDriver == 'imagick') {
            ImagerService::$compositeKeyTranslate['blend'] = \imagick::COMPOSITE_BLEND;
            ImagerService::$compositeKeyTranslate['darken'] = \imagick::COMPOSITE_DARKEN;
            ImagerService::$compositeKeyTranslate['lighten'] = \imagick::COMPOSITE_LIGHTEN;
            ImagerService::$compositeKeyTranslate['modulate'] = \imagick::COMPOSITE_MODULATE;
            ImagerService::$compositeKeyTranslate['multiply'] = \imagick::COMPOSITE_MULTIPLY;
            ImagerService::$compositeKeyTranslate['overlay'] = \imagick::COMPOSITE_OVERLAY;
            ImagerService::$compositeKeyTranslate['screen'] = \imagick::COMPOSITE_SCREEN;
            ImagerService::$ditherKeyTranslate['no'] = \Imagick::DITHERMETHOD_NO;
            ImagerService::$ditherKeyTranslate['riemersma'] = \Imagick::DITHERMETHOD_RIEMERSMA;
            ImagerService::$ditherKeyTranslate['floydsteinberg'] = \Imagick::DITHERMETHOD_FLOYDSTEINBERG;
        }
    }