Image Palette

An image palette refers to the variety of different colours available for use in an image. It defines what colours may be used, simplifying the pallette from th maximum of 16.7 million colours possible. This makes the amount of storage space required to store a bitmapped image much smaller.

Normally, storing an image takes 3 bytes for each pixel, plus whaterver else the format is using to define the image. This works out as one byte (8 bits, 256 possible values) for each colour, one byte for RED, one byte for GREEN, and one byte for BLUE, and it actually defines the displaying intensity for each colour (from 256 possibilities).

When an image palette is used however, instead of each colour being defined by 3 bytes, defining the intensity of each colour, it is defined by just one value (usually only one byte). This value is meaningless without the image palette, which then identifies the pixel value as a value within the palette, and displays that colour instead. This means that the image palette hold the RBG values for each colour instead of them being stored in each pixel.

The effect of this, is that an the size of an image is reduced (in most cases, using a palette of 256 colours, the image becomes about one third of the original size, approx. needing only one byte for every three normally needed). This method does require the conversion values to be stored somewhere, which basically means only compatible software can be used to view it.