index value in RGB image

hi.i have a code that use indexedImage.output image is a RGB image with index.for each pixel i have R,G,B and index value.what is index?what show index value?

Answer 1

[Image Analyst]

The first (left most) index is the row, the middle index is the column, and the last (right most) index is the color. Specify those to get the value of a certain color channel at a certain location:

blueValue = rgbImage(row, column, 3);  % Extract the blue value at this row,column location.

[fereshte]

you write a code for me in this link: http://www.mathworks.com/matlabcentral/answers/uploaded_files/14115/test.m

can you explain me labeledImage in above code? why R,G,B values change in indexed image?and what does index?

thanks

[Image Analyst]

Normally you would not do connected components labeling on an indexed image. It doesn't make sense. If I did that it must have been because you directly asked for it, but I would not normally do that since thresholding an indexed image is nonsense.

[Paul]

Hi Image Analyst, How can I refer to the value of "index". For example, if I want to change the color of a pixel based on the "index" value, how can I do it? To be clear, this is what I want to do: e.g:

    for i = 1 : length(image(:,1))
        for j = 1: length(image(1,:)) 
            if "index"(i,j) == 127
                image(i,j) = 1;
            else
                image(i,j) = 0;
            end
         end
    end

Thanks in advance. Paul

[Image Analyst]

Don't name your image "image" - that's the name of a built-in function. To do what you tried to do, you simply use logical indexing:

grayScaleImage = grayScaleImage  == 127;

Don't do any of those for loops, just do the one line above. It will set all original pixels with value of 127 to 1, and any other intensity will be set to 0.

[Paul]

Thanks Image Analyst. Maybe I was not clear enough. Let me use the image from fereshte (with your permission fereshte) to explain what I am trying to do (See the attached Image). We can see from this image that, we have:

• first line ---> X: 21 Y: 42
• 2nd line ---> Index: 148
• 3rd line ---> RGB: 0.651, 0.651, 0.651

What I am trying to do is to change the value of each pixel with the Index = 148 in the image to 1 for example and assign 0 to all other pixel with different Index value. Please note that, when I am saying "Index", I am talking about the "Index" value in the 2nd line of the above bullets (corresponding to the Data cursor displayed in the image, in this case, Index = 148). Thanks again. Paul

[Image Analyst]

OK, if it's an RGB image, then

grayScaleImage  = rgbImage(:,:,2); % Extract one of the color channels.
grayScaleImage = uint8(255 * (grayScaleImage  == 148));
% Make a new RGB output image
rgbOut = cat(3, grayScaleImage, grayScaleImage, grayScaleImage);

[Paul]

Thanks!

[Sudheendran Vasudevan]

Hi Image Analyst,

I have a dead peixel in my image how to remove that

[Image Analyst]

You can use a modified median filter to get rid of salt and pepper noise. I'm attaching the demo for that.

[Vijaya yaduvanshi]

hi Image Analyst,

Im having Matlab 2015a version. In this version Nonlocal mean filter is not available for prepossessing step of my oral cancer images.Please tell me another filter of same quality.

[Image Analyst]

I don't know. Just look around - there's medfilt2(), conv2(), imfilter(), etc.

[Vijaya yaduvanshi]

All right.

Thank You so much