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YUV values in grayscale images

asked 2015-03-12 05:02:44 -0500

begueradj gravatar image

YUV color space equations are done by:

image description

This leads to:

Y=(0.492*B - U)/0.492
Y=(0.877*R - V)/0.877

In the case of a grayscale image, U = V = 0. This means (by replacing in the equations above) Y= R= B. What does this means ? That Blue and Red colors are the same ?

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yes, in a grayscale image R=G=B (=Y). That's why it's grayscale and not color!

But next time please RTFM or wikipedia or whatever, before filling the forum with basic questions about the YUV color space, which is not related to OpenCV! !!!HERE!!!

kbarni gravatar imagekbarni ( 2015-03-12 05:42:52 -0500 )edit

@kbarni: He already got the equations and just asked to check his conclusions. I think this is a valid and good question and also of course related to OpenCV.

FooBar gravatar imageFooBar ( 2015-03-12 05:49:09 -0500 )edit

Sorry I got a bit emotional, but this is the 15th question he's asking in one week about the basics of the YUV color space. He could figure out this thing based on the answers he already got here in the forum.

kbarni gravatar imagekbarni ( 2015-03-12 05:54:03 -0500 )edit

instead of being angry, may be you can answer to my comment on an answer you gave me @kbarni

begueradj gravatar imagebegueradj ( 2015-03-12 06:03:25 -0500 )edit

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answered 2015-03-12 07:56:33 -0500

thdrksdfthmn gravatar image

You may answer your question by asking yourself what does U=V=0 means.

U and V are linked to the crominace (color), so if they are 0 (there is no crominance, so no color), then you'll have just Y.

That, in RGB case (light; and here be careful: adding light is different than adding colors on paper), means that all the colors have the same value (= to Y, the luminance)

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Asked: 2015-03-12 05:02:44 -0500

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Last updated: Mar 12 '15