+ double visibleRegionFillRatio = Math.max(getBounds().width / visibleRegion.width, getBounds().height / visibleRegion.height);
+ double alphaFactor = map(visibleRegionFillRatio, maxVisibleRegionFillRatioForAlpha0, minVisibleRegionFillRatioForAlpha1, 0, 1);
+ alphaFactor = Math.max(0, Math.min(1, alphaFactor));
+ // we need to take the old alpha into account to support nested submodules better.
+ int oldAlpha = gc.getAlpha();
+ gc.setAlpha(Math.max(0, Math.min(255, (int) (oldAlpha * alphaFactor))));