The Reason for this would be that then any Java app loading an image resource could use JPEG XLs without changing its code - the only thing needed would be to put one more jar into the classpath...

I would be willing to participate in the effort as i wrote a few ImageIO codecs already - though not as complex ones as would be needed here...

One could maybe get inspiration for example from here: https://xmlgraphics.apache.org/batik/javadoc/org/apache/batik/ext/awt/image/codec/imageio/ImageIOJPEGImageWriter.html