ntsc2rgb

Convert NTSC values to RGB color space

Syntax

RGB = ntsc2rgb(YIQ)

rgbmap = ntsc2rgb(yiqmap)

Description

RGB = ntsc2rgb(YIQ) converts the luminance (Y) and chrominance (I and Q) values of an NTSC image to red, green, and blue values of an RGB image.

rgbmap = ntsc2rgb(yiqmap) converts an NTSC colormap to an RGB colormap.

Examples

Convert Image from YIQ to RGB

This example shows how to convert an image from RGB to NTSC color space and back.

Read an RGB image into the workspace.

RGB = imread('board.tif');

Convert the image to YIQ color space.

YIQ = rgb2ntsc(RGB);

Display the NTSC luminance, represented by the first color channel in the YIQ image.

imshow(YIQ(:,:,1))
title('Luminance in YIQ Color Space')

Convert the YIQ image back to RGB color space.

RGB2 = ntsc2rgb(YIQ);

Display the image that was converted from YIQ to RGB color space.

figure
imshow(RGB2)
title('Image Converted from YIQ to RGB Color Space')

Input Arguments

YIQ — NTSC image

m-by-n-by-3 numeric array

NTSC image, specified as an m-by-n-by-3 numeric array with values in the range [0, 1]. The third dimension of YIQ defines the luminance (Y) and chrominance (I and Q) for each pixel, respectively.

Data Types: double

yiqmap — NTSC colormap

c-by-3 numeric matrix

NTSC colormap, specified as a c-by-3 numeric matrix with values in the range [0, 1]. The value of c corresponds to the number of colors in rgbmap. Each row of yiqmap is a three-element YIQ triplet that specifies the luminance (Y) and chrominance (I and Q) components of a single color in the colormap.

Data Types: double

Output Arguments

RGB — RGB image

m-by-n-by-3 numeric array

RGB image, returned as an m-by-n-by-3 numeric array with values in the range [0, 1]. The third dimension of RGB defines the red, green, and blue intensity of each pixel, respectively.

Data Types: double

rgbmap — RGB colormap

c-by-3 numeric matrix

RGB colormap, returned as a c-by-3 numeric matrix with values in the range [0, 1]. Each row of rgbmap is a three-element RGB triplet that specifies the red, green, and blue components of a single color in the colormap.

Data Types: double

Algorithms

In the NTSC color space, the luminance is the grayscale signal used to display pictures on monochrome (black and white) televisions. The other components carry the hue and saturation information. The value 0 corresponds to the absence of the component, while the value 1 corresponds to full saturation of the component.

ntsc2rgb computes the RGB values from the NTSC components using

$$\left[\begin{array}{c}R\\ G\\ B\end{array}\right]=\left[\begin{array}{ccc}1.000& 0.956& 0.621\\ 1.000& -0.272& -0.647\\ 1.000& -1.106& 1.703\end{array}\right]\left[\begin{array}{c}Y\\ I\\ Q\end{array}\right].$$