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How to read the RGB value from a grayscale image (just like the data cursor does)

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Penny
Penny 2017-2-28
回答： Image Analyst 2017-3-1
I have a DICOM image. I have read it and stored the value in variable 'I'. So, how to read the RGB value from a grayscale image (just like the data cursor does). Here is the image with the data cursor. Variable 'I' is consisted of the index values shown in the second line on the picture. I wonder whether we can read the RGB value by command just like the third value shown on the image. If yes, how to do it? Thanks a lot

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Walter Roberson
Walter Roberson 2017-2-28
cmap = colormap();
RGB = ind2rgb(YourImage, cmap);
RGB(290, 189) %notice that X is columns and Y is rows
However, if you used imshow() to display the image, then chances are that imshow decided on the colormap for you instead of using the current colormap. If so, then instead of assigning colormap() to cmap, use
cmap = gray(256);
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Penny
Penny 2017-3-1
thanks to Adam and Walter. It works by using the function mat2gray. But how to define the amin and amax value that correspoing to 0 and 1 in grayscale image? we have several nomalized value in 'Image' that corrsponding to 1. How to define the minimum one? thanks a lot to your help.
Penny
Penny 2017-3-1
If I use the function mat2gray by the default setting,the code is
if true
Image=dicomread('D:\CT\001\001.dcm');
figure;
imshow(Image,[]);
I=mat2gray(Image);
figure;
imshow(I,[])
end
But the value has a little difference to the data cursor. Here is the picture:

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更多回答（2 个）

Chad Greene
Chad Greene 2017-3-1
Alternatively, I wrote a function for this a while back. It's been a while since I wrote it, so no guarantees regarding how well it works. It's called colorpicker.
Image Analyst
Image Analyst 2017-3-1
The function you want is called impixelinfo():
hp = impixelinfo();
set(hp, 'Units', 'normalized');
set(hp, 'Position', [.5, .9, .3, .05]); % Or whatever size and location you want.
This will put up a status label where you can see the x,y and RGB values as you mouse around over the image.

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