Barco Argus X Terminal User Manual

Also see for Argus X Terminal: User manual

Contents

Barco Argus X Terminal User Manual Manual pdf 77 page image

4. OperatingBarco – Argus X Terminal – DOC-3265-2 – user's manual – Revision 04 – May-2004 _________________________________________________________________________ 4-34.2 Color management4.2.1 Basic understandingThe translation between RGB values specified in applications and the color displayed on-screen is controlled bypixel values serving as indices to a color map. The application obtains the pixel values from the X window sys-tem.RGB valuesRGB values are the red, green and blue intensity values that are used to define a color. According to the X.11protocol these values are represented as 16-bit, unsigned numbers, with 0 the minimum intensity and 65535 the0 the minimum intensity and 65535 themaximum intensity. Most hardware however represents each value as a number in the range from 0 to 255.Color mapA color map consists of a set of numbered entries – so called color cells – defining pixel values. Each color cellcontains a single RGB triple – a combination of RGB values. The color map will be filled at runtime.X.11 supports two ways for handling color maps:• shared color cellColors that can be used by different X clients are called shared colors. A color that was once allocated can notbe changed. When an X client is requesting for a shared color the X server searches the color map for exactlythe requested color (exact match). If the color is not found a new color will be allocated in the color map.• private color cellA color that can only be used by one client is considered to be a private color. Only the client that allocated itcan use a private color. A client is able to change the contents of a private cell. As long as entries are avail-able in the color map, private colors can be allocated.Color depthOn a black-and-white screen, each pixel is represented with a single binary digit, i. e. a color depth of 1. Manycolor workstations have a color depth of 8bit, each pixel on such a screen is represented by eight bits, allowing8bit, each pixel on such a screen is represented by eight bits, allowing2 8= 256 on-screen colors. A color depth of 24 bits corresponds to 2 24= 16.7 million (16M) colors and is said tocover all shades of colors the human eye can distinguish.