How to use colormap() for a vector of images X in order to display indexed images from vector X?

I have made a Neural network for clothes color matching. It uses indexed images of clothes stored in a vector X. when I try to display these indexed images they appear to be pale instead of colored. I am using a custom function displayData for display. Although Neural network with indexed images is working correctly (with reasonable accuracy) but it displays to user only pale images in beginning and during testing. I came to know that somewhere I should use colormap() function. I called colormap() right after calling displayData but it does not work

fprintf('Loading cloth Data\n')

load('myclothingdata.mat');
m = size(X, 1);

[sel] = randperm(size(X, 1));
sel = sel(1:100);
displayData(X(sel, :));
% colormap() 
fprintf('Press enter for next step.\n');

It calls the following displayData function

https://github.com/aptiva0985/MachineLearning-Andrew-Ng-Coursera-/blob/master/ML003/mlclass-ex3/displayData.m

the output is as follows, showing indexed images of clothes

[Benjamin Kraus]

It would be helpful if you uploaded a copy of myclothingdata.mat as a MAT file, assuming it is small enough.

If you cannot upload the file, can you describe the format of the data in more detail. For example:

1. What are the dimensions.
2. What are the min and max of the data.
3. Is the data double or some other type?

Can you also clarify: Is the image you posted the result you see after running the code with the colormap function or without?

Finally, what version of MATLAB are you running?

[jawad ashraf]

I have uploaded the file myclothingdata.mat.

I see this pale result both with and without function colormap() but I dont use colormap(map) because it gives this error >> Undefined function or variable 'map'.

I am using R2012b version of MATLAB

[jawad ashraf]

Now I have attached ClothingNeuralNetwork zip file that comprises complete coding files of project minus myclothingdata.mat which I have attached separately in above comment.

you please include myclothingdata.mat in this parent scripting folder and then run MainFile.m on MATLAB.

[jawad ashraf]

New post link

https://www.mathworks.com/matlabcentral/answers/418072-how-to-display-indexed-images-from-mat-file-using-colormap

Answer 1

[Benjamin Kraus]

The issue you are encountering is that displayData is normalizing the image data so that the maximum value of each image is equal to 1. It is then using imagesc to display the image using the full range of the colormap. Because your image is indexed and using a special map, the map is being lost by normalizing the data.

Unfortunately, I don't think you are going to be able to use displayData unmodified, it just isn't designed to handle indexed images.

However, you could try something potentially better. displayData is relying on -1 being a special value, which it is using to display gray lines. Because you are working with indexed colors, you can just add a gray/black color to the end of your map. Relatively small changes to displayData should allow you to get this working.

For example:

1. Replace -1 (Setup blank display) with the last color in your map, max(X(:)+1.
2. Remove the normalization using max_val.
3. Replace the call to imagesc with just a regular call to image.

[jawad ashraf]

Is there need to have a colormap matrix in myclothingdata.mat along with X(indexed images vector) and Y(target labels)? currently I have

myclothingdata.mat = X(inddexed images) + Y(target labels)

should have I the following way

myclothingdata.mat = X(inddexed images) + A colormap matrix for every image + Y(target labels) ?

I am lacking the second component(colormap) in myclothingdata.mat. Should I include it or just modification of displayData will work as you have suggested??

[Benjamin Kraus]

My previous answer should give you enough to update displayData, so try that first.

If you can't get it working and want more assistance, you may want to add the map to the MAT-file, and make sure to update the post to describe what new things you have tried and what issue you are running into.

[jawad ashraf]

I tried what you suggested but it did not work. You please check it yourself and if you make required changes I will be Obliged to you as this is my first project in MATLAB and I can't understand much things.

[Benjamin Kraus]

"If you can't get it working and want more assistance ... make sure to update the post to describe what new things you have tried and what issue you are running into."