Home Page | Up One Level | Site Map | Send Us email


What a CD-i Color Look Up Table looks like:


CLUT Image Formats

The CLUT (also called pallete) maps each pixel in the picture to a particular entry in the table. Each entry in the table stores an RGB color--one of 17 million colors in the player's pallete. For example, a CLUT 7 image has 128 table entries, permitting 128 possible colors in the picture. It is up to the picture designer and the paint application to map each pixel to a table entry (color). If the original picture contains more colors than there are table entries (128 in our example), then most paint packages will peform "color reduction". Pixels of similar hue and brightness will be homogenized to some comprimise color, and that color (and associated pixels) assigned to a CLUT entry. This process continues until all pixels in the picture (up to 107,520) are mapped to one of 128 CLUT entries. At best, the resulting picture is visually identical or at least estehtically similar to the original. At worst, there is severe "banding", where suble color gradations in the original, like sky or flesh, become a few rainbow-like color bands.

There are five CD-i picture formats that use a CLUT. They are:
Note: that for special effects on a CD-i player, desired transparent or text colors must be placed in certain table entries. Your desired transparent color must be in table entry 0, while the primary text color (for presenting changing text in a title) must be in entry 1. Use a paint application or video conversion tool, like DeBabelizer, to arrange the palette accordingly.
The graphic below was designed to fit horizontally on an 8.5x11 page. Use landscape print mode to make a hard copy.

Home Page | Up One Level | Site Map | Send Us email