Craft\ImagerService::_applyBackgroundColor PHP Method

    private function _applyBackgroundColor(\Imagine\Image\ImageInterface &$imageInstance, $bgColor)
    {
        $palette = new \Imagine\Image\Palette\RGB();
        $color = $palette->color($bgColor);
        $topLeft = new \Imagine\Image\Point(0, 0);
        $backgroundImage = $this->imagineInstance->create($imageInstance->getSize(), $color);
        $backgroundImage->paste($imageInstance, $topLeft);
        $imageInstance = $backgroundImage;
    }