matlab - Green component after setting Y,Cb and Cr to zero -


i setting y, cb , cr 0 , converting rgb using matlab. don't understand why getting red , blue component 0 in rgb color space while green component has value 132?

edit: (code comment):

i1 = imread('img.jpg');  img = rgb2ycbcr(i1);  lumin = img;  lumin(:,:,1) =0;  lumin(:,:,2) =0;  lumin(:,:,3)=0;  figure,imshow(lumin);  rgn = ycbcr2rgb(lumin);  figure,imshow(rgn);

conversion formulas between rgb , ycbcr involve offsets. if zeros in 1 domain not zeros in other domain. if directly use formula convert 0 ycbcr domain matrix rgb positive green values , negative red , blue values. these negative values thresholded 0 seeing.

the wikipedia page http://en.wikipedia.org/wiki/ycbcr , matlab color space conversion block reference page @ http://www.mathworks.com/help/vision/ref/colorspaceconversion.html shows formulas used.


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