imread png vs gif

It looks imread .gif and .png are different. Please help to read the image right.

    [X,map] = imread('matlabicon.gif');
    icon = ind2rgb(X,map);
    % X is 16x16, map is 127x3
    image(icon);

image(icon) looks good!

However:

      [X,map] = imread('open_file.png');
      % X is 16x16x3, map=[]
      icon = ind2rgb(X,map);
      % doesn't work as map=[] and X is already 3 dimensions

image(X) doesn't look the same image at all! White pixels became black.

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Added on after a while:

OK, I did this, and it looks about right. CData in uipushtool shows correctly:

      X(X==0)=max(X(:));
      icon = double(X)/double(max(X(:)));

But it doesn't look elegant and generally right.

What's the right way of reading all image format for image(X) and CData in uipushtool?

Answer 1

[Image Analyst]

Please attach your open_file.png file so we can help you. If X is already an RGB image (16x16x3) then a colormap does not even apply, and you certainly shouldn't use ind2rgb() on an image that is ALREADY RGB.

[John]

All files are in: C:\Program Files\MATLAB\"R2013b"\toolbox\matlab\icons

[Image Analyst]

open_file.png is not in R2013b. It must have been something you added. It doesn't ship with MATLAB because I don't have it and I have that version and also the latest R2014b and it's not in that either. Please attach your open_file.png file so we can help you.