Color Graphics Adapter (CGA)
The first color capable video card for the IBM PC family was the Color Graphics Adapter (CGA), which includes two graphic modes: 320×200 pixels with four colors (two bits per pixel) and 640×200 pixels black-and-white (one bit per pixel). The card as a whole implemented the "digital RGBI" 16-color space, i.e. each primary color (red green and blue) could be either on or off for a given pixel, and an additional intensity bit would brighten all three primaries if it was turned on for a pixel.
The color mode uses two bits to store red and green 1-bit components for each pixel (that is, colors in the RG color space) while the blue and intensity components were fixed for the entire screen.
This gave four possibilities for each single pixel: background (any one of the 16 colors the system offered, black or blue was most used; however only one background color could be chosen for the entire screen), red, green and yellow, with two possibilities of intensity selectable for the entire screen (except the background): low (darker) and high (lighter). This was known as Fixed palette #2. The Fixed palette #1 adds the blue component to all colors except the background, giving background (usually black was chosen), magenta (red+blue), cyan (green+blue) and white (yellow+blue), with two possible intensities, too.
|
Read more about this topic: RG Color Space
Famous quotes containing the word color:
“He could jazz up the map-reading class by having a full-size color photograph of Betty Grable in a bathing suit, with a co- ordinate grid system laid over it. The instructor could point to different parts of her and say, “Give me the co-ordinates.”... The Major could see every unit in the Army using his idea.... Hot dog!”
—Norman Mailer (b. 1923)