This repository shows how to do "smart" color inversion on Linux.
The general idea is to transform black-on-white texts to white-on-black, which may reduce the stress on your eyes, especially in dark environments.
There are many ways to do "color inversion" though:
| Name | First image (editor) |
Second image (color chooser) |
Third image (gimp chooser) |
|---|---|---|---|
| Original Image |  |
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| RGB negation |
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| Matrix (halfs) |
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| Matrix (thirds) |
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| RGB shift |  |
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| RGB shift lowcontrast |  |
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The simplest, but probably also the worst.
Black becomes white and vice versa. Color (r,g,b) transforms to (1-r, 1-g, 1-b). It can be applied to your system by installing xcalib, and running xcalib -i -a. To restore, type the same command again.
This is a relatively good approach, although it does lose some quality (see below).
The idea is to make each (r,g,b) component to be a linear function from original r,g,b values.
The "Matrix (halfs)" picture was generated by the formula: (new_red = 1 - (1/2)*green - (1/2)*blue)
The "Matrix (thirds)" picture was generated by the formula: (new_red = 1 + (1/3)*red - (2/3)*green - (2/3)*blue)
See below on how to enable this color transformation on Linux (compton).
References: these color transformations are also implemented in the Windows application NegativeScreen. I studied those repo matrices while doing this comparison.
This approach preserves the "color" (hue) and maintains color richness (the transformation is a bijection from RGB color space to itself).
Technically, this transformation is the same as doing 180-degree HUE rotation combined with RGB negation.
See below on how to enable this color transformation on Linux (compton). You can test it on images with GIMP:
- Menu > Colors > HueSaturation > Hue > 180 > OK.
- Menu > Colors > Invert
Same as RGB shift, but lightens darker colors, making black only a dark gray. This is because it is actually hard for the eye to read absolutely white letter near absolutely black background. The contrast (black against white) blinds you a bit. Having at least some light coming from background helps a lot (in my opinion).
In order to bring these niceties to your system do:
- Install
comptoncompositor - Clone this repo (or download the *.glsl files)
- Go into the directory containing the *.glsl files
- Launch the compositor with:
compton --backend glx --glx-fshader-win "$(cat shift_whiteish.glsl)" --invert-color-include id!=0 - If you use subpixel order for your fonts, consider inverting them simultaneously, too (RGB should become BGR and vice-versa).
If you want to try out other transformations (like matrices, or maybe some of your own glsl), just insert a different file into the command above.
Warning: This will replace your current (xfce/gnome/kde/i3/whatever) compositor. Non-permanently, so if you're not satisfied, kill the compositor and/or start your old one back. Alternatively, log out and log in back.
To the best of my knowledge, these approaches do NOT work:
- XRenderer
- gamma ramps modifications (because they are color-independent)
- xcalib modifications, because it uses gamma ramps
- and actually everything non-OpenGL-based.
Some discussion on Wayland support can be found here.
MacOS users had an option for RGB shift, but seemingly lost it in 2014: lswank/Tranquility#9
Reported to be working:
- ubuntu
compizcompositor along with a manually compiled "Color Filter" plugin. https://ubuntuforums.org/showthread.php?t=1419702
A future work might be to find some "colorfullness"-preserving algorithm, in addition to preserving hue and doing some form of brightness inversion. If interested, see wikipedia for "colorfullness" and prepare yourself to experiment with glsl code.
- The
compizplugin and the ubuntu forum for showing that the task is possible, and showing it should be OpenGL-based - Compton developers
- NegativeScreen(Windows) developers for providing analysis, matrix examples
- Kurnevsky Evgeny for suggesting and explaining on how to use compton for such a task.