How to find the highest gray value in a color image?

How do we find the highest gray values in a color image. If this highest gray value in certain channel, for example, further, how do we find out other locations which have highest gray value?

Answer 1

[Walter Roberson]

grayimage = rgb2gray(YourRGBImage);

maxgray = max(grayimage(:));

grayidx = find(grayimage == maxgray);

These are the linear indices. If you want row and column instead then use

[grayidxrow, grayidxcol] = find(grayimage == maxgray);

[matlabgeek]

Thanks. This is what I want

[matlabgeek]

If [grayidxrow, grayidxcol] has only one value individual, so this means there is only one location has maxgray?

[Walter Roberson]

Correct.

[Image Analyst]

If by "highest gray value in certain channel" then you mean the highest red value, the highest green value, and the highest blue value, then you'd to that on each color channel independently.

maxR = mean2(rgbImage(:,:,1));
maxG = mean2(rgbImage(:,:,2));
maxB = mean2(rgbImage(:,:,3));

Of course the highest in each channel may not all lie at the very same pixel. The brightest red value may lie at a different place than the highest blue value.