- Draw border around links
Whether to draw a border around links.
- Change colors
Enables the color changing options.
- Color mode
Defines the color changing mode.
- Invert Colors
Inverts colors on the view, i.e. black objects will be shown white.
- Change Paper Color
Changes the paper's color, i.e. the document's background.
The color can be selected using the Paper color swatch below.
- Change Dark & Light Colors
Changes the dark and light color to your preference, that means black will not be rendered as black but as the selected dark color and white will not be rendered as white but as the selected light color.
- Convert to Black & White
Converts the document to black and white. You can set the threshold and the contrast. Setting the threshold to a higher value by moving it to the right will result in lighter grays used.
- Invert Lightness
Inverts lightness of all colors. Light and dark colors will be swapped, but hue and saturation will not be affected. The Contrast in images will usually be worse than in Invert Luma (sRGB Linear).
- Invert Luma (sRGB Linear)
Inverts luma of all colors. Light and dark will be swapped, but hue and saturation will not be affected. The Contrast in images is preserved better than in Invert Lightness, but graphics and colorful text markup usually look worse. Uses sRGB luma coefficients, but no gamma correction.
- Invert Luma (Symmetric)
Inverts luma of all colors, using symmetric luma coefficients. Light and dark will be swapped, but hue and saturation will not be affected. Very similar to Invert Lightness, but the contrast is in some cases better.
- Shift Hue Positive
Shifts hue of all colors by 120 degrees. Can mitigate some contrast problems in colorful graphics.
- Shift Hue Negative
Shifts hue of all colors by 240 degrees. Can mitigate some contrast problems in colorful graphics.
You can configure keyboard shortcuts and toolbar actions for the color modes using the corresponding menu items in the menu of the Okular main window.
- Text-to-speech engine
Allows you to choose the text-to-speech (TTS) engine to be used by Okular. The default is speechd TTS, but you can use all languages and voices depending on the available synthesizers on your platform. On Linux®, speech-dispatcher is used by default to determine available voices.