When talking about the Targa TGA file format, a number of terms are encountered quite frequently. These terms are defined below:
Direct Color each pixel value is sub-divided into red, green and blue fields which are used as separate indices to access independent, programmable lookup tables. The outputs of the individual color maps directly determine the intensities of each primary color. A direct-color system is similar to pseudo-color except that the values in the color maps can be altered individually for the red, green and blue channels; whereas the red, green and blue values in a pseudo-color system are loaded into one map which is accessed by a single index. Truevision products that use this type of image are: ATVista and NuVista video boards.
Pseudo Color each pixel value is used as a single index into a programmable color map which contains the actual red, green and blue intensities to be displayed. The Truevision products that use this type of image are: VDA, VDA/D, Targa M8, ATVista, NuVista and HR video boards.
True Color each pixel value is sub-divided into red, green and blue fields that directly determine the intensities of each primary color. The Truevision products that use this type of image are: ICB, Targa 16, Targa 24, Targa 32, ATVista and NuVista video boards.
Note: the VDA, VDA/D, Targa M8 and HR can only be operated as pseudo-color devices. The ICB, Targa 16, 24 and 32 video boards can only be used as true-color devices.