Image Processing Toolbox

NTSC Color Space

The NTSC color space is used in televisions in the United States. One of the main advantages of this format is that grayscale information is separated from color data, so the same signal can be used for both color and black and white sets. In the NTSC format, image data consists of three components: luminance (Y), hue (I), and saturation (Q). The first component, luminance, represents grayscale information, while the last two components make up chrominance (color information).

The function rgb2ntsc converts colormaps or RGB images to the NTSC color space. ntsc2rgb performs the reverse operation.

For example, these commands convert the flowers image to NTSC format.

• RGB = imread('flowers.tif');
  YIQ = rgb2ntsc(RGB);
  

Because luminance is one of the components of the NTSC format, the RGB to NTSC conversion is also useful for isolating the gray level information in an image. In fact, the toolbox functions rgb2gray and ind2gray use the rgb2ntsc function to extract the grayscale information from a color image.

For example, these commands are equivalent to calling rgb2gray.

• YIQ = rgb2ntsc(RGB);
  I = YIQ(:,:,1);
  

Note    In YIQ color space, I is one of the two color components, not the grayscale component.

Converting to Other Color Spaces

YCbCr Color Space