Instafilter\Filter::brightness_contrast PHP Method

    public function brightness_contrast($brightness, $contrast)
    {
        //normalise from photoshop's units to imagicks -- this is a guestimate
        $brightness_normalised = abs($brightness) / 150 * 5;
        $contrast_normalised = abs($contrast) / 150 * 5;
        if ($contrast_normalised == 0 and $brightness_normalised == 0) {
            return $this;
        }
        $overlay = new \Imagick();
        $overlay->newPseudoImage(1, 1000, "gradient:");
        $overlay->rotateImage('#fff', 90);
        if ($contrast_normalised != 0) {
            $overlay->sigmoidalContrastImage($contrast > 0, $contrast_normalised, 50);
        }
        if ($brightness_normalised != 0) {
            $overlay->sigmoidalContrastImage($brightness > 0, $brightness_normalised, 0);
        }
        $this->imagick()->clutImage($overlay);
        return $this;
    }