ntsc2rgb

Convert NTSC values to RGB color space

Syntax

RGB = ntsc2rgb(YIQ)

Description

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

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 — YIQ color values

numeric array

YIQ color values to convert, specified as a numeric array in one of these formats.

• c-by-3 colormap. Each row specifies one YIQ color value. Values should be in the range [0, 1] with data type double.

• m-by-n-by-3 image. Values can be data type single, double, uint8, uint16, or int16.

Attribute	Description
Y	Luma, or brightness of the image. Values are in the range [0, 1], where 0 specifies black and 1 specifies white. Colors increase in brightness as Y increases.
I	In-phase, which is approximately the amount of blue or orange tones in the image. I in the range [-0.5959, 0.5959], where negative numbers indicate blue tones and positive numbers indicate orange tones. As the magnitude of I increases, the saturation of the color increases.
Q	Quadrature, which is approximately the amount of green or purple tones in the image. Q in the range [-0.5229, 0.5229], where negative numbers indicate green tones and positive numbers indicate purple tones. As the magnitude of Q increases, the saturation of the color increases.

Data Types: single | double | uint8 | uint16 | int16

Output Arguments

RGB — Converted RGB color values

numeric array

Converted RGB color values, returned as a numeric array of the same size as the input. Values are in the range [0, 1]. The output data type is double unless the input data type is single, in which case the output data type is also single.

Data Types: double | single

Algorithms

ntsc2rgb computes the RGB values from the NTSC components using

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