Posted by martinezmj on
URL: https://forum.jogamp.org/Problem-with-glReadPixels-on-OS-X-retina-display-tp4033426p4033427.html

This appeared to fix it:
canvas = new GLCanvas(caps);
canvas.setSurfaceScale(new int[] { ScalableSurface.IDENTITY_PIXELSCALE, ScalableSurface.IDENTITY_PIXELSCALE });