CMAP_FULL Color Map

When the entire color map is available, Starbase uses standard 3:3:2 direct color (CMAP_FULL mode) in 8-plane visuals. With the SB_X_SHARED_CMAP set, only 216 entries of the color map are available for direct color support.

Starbase defines these entries as follows:

The standard 3:3:2 indicates that three bits are set aside for red, three for green and two for blue. This is the same color map that is used on other 8-plane devices.

The standard 6|6|6 means that the color map contains all combinations of six levels of red, green and blue. This yields a total of 6x6x6 = 216 colors. Color levels are evenly spaced from black (i.e. zero intensity) to white (i.e. full intensity) using the following values: 0.0, 0.2, 0.4, 0.6, 0.8, 1.0 .

The entries between 40 and 255, inclusive, are used for the direct color map with SB_X_SHARED_CMAP enabled. They are defined according to the following algorithm:

    int index;
    CMAP shared_color_map[256];
    float red_level,
          green_level,
          blue_level;
    . . .
 
    index = 40;
	 	 	 	 for (red_level = 0.0; red_level <= 1.0; red_level += 0.2)
	 	 	 	 for (green_level = 0.0; green_level <= 1.0; green_level += 0.2)
	 	 	 	 for (blue_level = 0.0; blue_level <= 1.0; blue_level += 0.2)
           {
            shared_color_map [index].red_component = red_level;
            shared_color_map [index].green_component = green_level;
            shared_color_map [index].blue_component = blue_level;
            index++;
           }

This is known as the standard 6|6|6 organization for the color map.

The CRX, Dual CRX, CRX-24, CRX-24Z, and integrated graphics workstations (HP 705/710/715/725) color devices provide support for both the 3:3:2 and 6|6|6 CMAP_FULL color maps. The standard 3:3:2 color map is supported in X11 windows when the SB_X_SHARED_CMAP mode is off. The 6|6|6 color map mode is available in X11 Windows when the SB_X_SHARED_CMAP mode is on.

	NOTE: The hpgcrx driver supports CMAP_FULL mode in depth 24 windows on the CRX-24. It also supports CMAP_FULL mode in depth 8 windows on the same device for compatibility with other devices. Performance is better with depth 24 windows. We strongly discourage use of CMAP_FULL in depth 8 windows on the CRX-24.