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Visuals and Resolutions
A display screen. is made up of pixels. Each pixel identifies a point on the screen and carries color information. The amount of color information a pixel can carry is identified by its depth, i.e. the number of bits it has, to store this information. For example, a depth of 1 means that only two colors are possible, either black or white, with no shades of gray.
An X application uses pixel indices to store, retrieve or use color information. Pixel indices reference entries in a colormap, which is a store of colorcells. The method by which a color index is used to get to the displayed color in a colormap is determined by the visual classes.
There are five visual classes that are possible: Static color, pseudo color, static gray, gray scale and true color. For instance, static color and static gray mean that the color entries are preset and cannot be modified by an application. Static Gray and Gray Scale give only shades of gray.
The X Server offers the X application a subset of the visual classes, depending on the correct display and settings of your workstation table. If you change the display settings of your workstation, you should select the visual once more. If you do not, and then the server detects a conflict between the display settings and visual class it will prompt you to change the visual class.
When should the Pseudo color visual be used on the desktop?
If your windows workstation has a setting of 256 colors, the windows uses a system palette for sharing colors across applications. Only if a color is present in a system palette, then it can be displayed on the screen. This scheme is also referred to as pseudo color in X terminology application.
When should the True color visual be used on the desktop?
When your workstation is set to > 256 colors, a true color scheme is used. In time color, there is no system palette. The applications use an RGB value to define a color. This value is used directly and the R, G and B values can be varied independently.
X Application can use names to identify a color value. For example, Light Gray would be used for the color value ( 192,192,192) i.e. (R= 192, G= 192 & B= 192). The color database stores the names for over 750 colors.
If your application is displaying a single color, incorrectly, then it could be that it is using a name that is not present in the database. You could rectify this by adding the name to the color database through the X Config application.
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2002 Frontier Technologies Corporation. All rights reserved |