ntsc2rgb

Convert from NTSC/YIQ to RGB colorspace

Calling Sequence

RGB = ntsc2rgb(YIQ)

Parameters

YIQ: A NTSC image (hypermat). The dimension of NTSC should be M x N x 3, the type should be double and the element value range should be [0,1].
RGB: Output image, which has the same size as NTSC and type of double.

Description

ntsc2rgb converts an image or colormap in the YIQ colorspace to the RGB colorspace. The YIQ model is used in NTSC and European TV's. It is useful for b&w and color compatibility, since the cromaticity (I and Q) and luminance (Y) are conveniently isolated. ntsc2rgb(YIQ) uses the following operation to convert each YIQ triplet:

! R !   !  1.000  0.956    0.621   !   ! Y !
! G ! = !  1.000  -0.272   -0.647  ! * ! I !
! B !   !  1.000  -1.105   1.702   !   ! Q !

Supported classes: DOUBLE.

Example

initial_dir = PWD;
chdir (SIPDIR + 'images');

rgb = imread('tru.jpg');    // RGB colorspace 0-1
imshow(rgb);
yiq = rgb2ntsc(rgb);        // YIQ colorspace 0-1
yiq(:,:,2) = yiq(:,:,2) /4; // Decrease chromaticity
yiq(:,:,3) = yiq(:,:,3) /4;
rgb = ntsc2rgb(yiq);
imshow(rgb);

chdir(initial_dir);

Authors

Ricardo Fabbri <ricardofabbri[at]users.sf.net>

Availability

The latest version of SIP can be found at

http://siptoolbox.sf.net