public void setExpandGrayAlpha(boolean expandGrayAlpha) {
        this.expandGrayAlpha = expandGrayAlpha;
    }
If set, images containing one channel of gray and one channel of
alpha (GA) will be output in a 4-channel format (GGGA).  This
produces output that may be simpler to process and display.

<p> This setting affects both images of color type 4 (explicit
alpha) and images of color type 0 (grayscale) that contain
transparency information.

<p> By default, no expansion is performed.
plugins/svg-plugin/batik-codec-fix/src/main/java/org/apache/batik/ext/awt/image/codec/png/PNGDecodeParam.java