Magnifier: Brightness, Contrast, and Inversion
GNOME Shell has a built-in magnification feature. In addition to magnification, some low-vision users prefer to invert the lightness ("inverse video"), change the overall brightness, change the contrast, and/or some combination thereof. Further details are available in the development section of the GNOME Shell Magnification wiki page.
GNOME Shell team (patch review), clutter team (patch review), gsettings-desktop-schemas maintainers (patch review), a11y team
May 16, 2012
- Integration of Clutter brightness/contrast effect with GNOME Shell magnifier committed.
- Lightness inversion Clutter effect added to GNOME Shell and integrated with the magnifier.
GSettings for inversion, brightness, and contrast committed 645665#c9.
See "Screen shots" section below for examples of the effects. The initial plan was to release these features as part of GNOME 3.2, but delayed when the bright-contrast-inverse Clutter effects were moved from custom code in GNOME Shell to Clutter itself. During the 3.4 cycle the algorithms were discussed and improved; and it was suggested the inverse effect should be moved back to GNOME Shell. Thus the work was not completed in time for 3.4.
The work is tracked with three bugs:
Magnifier: Add brightness and contrast functionality (gnome-shell).
Magnifier: Add brightness and contrast preferences (gsettings-desktop-schemas).
Figure one shows the lightness inversion effect. The bottom half of the screen is magnified and inverted. Note that the hues are the same (blue remains blue, orange is orange, etc.), but lightness is inverted. Compare the two views of the triangle in the colour picker, especially the left edge: Darker reds are lighter, lighter reds are darker, and grey levels are inverted.
Figure 1. Screen shot of lightness inversion effect.
Figure two shows the a +25 per cent increase in contrast. The bottom half of the image shows the enhanced contrast view.
Figure 2. Screen shot of contrast effect.
Related bugs and enhancements:
Add a grayscale effect (gnome-shell)
make 'zoom' independent of color-related shader use (gnome-shell)
Allow to control color-related shader options in the shell (gnome-control-center)