public void setOpacity(float opacity) {
        this.opacity = opacity;
    }
Adjusts the alpha channel of the incoming image
opacity: The value to multiply the incoming alpha channel for each pixel by (0.0 - 1.0, with 1.0 as the default)
dkplayer-sample/src/main/java/xyz/doikki/dkplayer/widget/render/gl2/filter/GlOpacityFilter.java