MATLAB VIDEO AND IMAGE PROCESSING BLOCKSET 3 Guide de l'utilisateur télécharger pdf (Page 105)

Chroma Resampling

The Y’CbCr color space separ ate s the luma (Y’) compon ent of an image from

the chroma (Cb and Cr) components. Luma and chroma, which are calculated

using gamma corrected R, G, and B (R’, G’, B’) signals, are different quantities

than the CIE chrominance and luminance. Because the human eye is more

sensitive to changes in luma than to changes in chroma, you can reduce the

bandwidth required for transmission or storage of a signal by removing some

of the color information. For this reason, this color space is often used for

digital e ncoding and transmission applications. In the following example, you

use the Chroma Resampling block to downsample the Cb and Cr components

of an image:

1 DefineanRGBimageintheMATLABworkspace. ToreadinanRGB

image from a TIF file, at the MATLAB command prompt, type

I= imread('autumn.tif');

I is a 206-by-345-by-3 array of 8-bit unsigned integer values. Each plane of

this array represents the red, green, or blue color values of the image.

2 To view the image this array represents, at the MATLAB command prompt,

type

imshow(I)

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MATLAB VIDEO AND IMAGE PROCESSING BLOCKSET 3 Guide de l'utilisateur Page 105