[Octave-bug-tracker] [bug #37689] imread strange result

[Rik]

Update of bug #37689 (project octave):

                  Status:               Need Info => Confirmed              

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Follow-up Comment #5:

Thanks for the example.  I can verify what Octave is doing.

Quoting from the documentation for imread


 -- Function File: [IMG, MAP, ALPHA] = imread (FILENAME)
     Read images from various file formats.

     The size and numeric class of the output depends on the format of
     the image.  A color image is returned as an MxNx3 matrix.
     Gray-level and black-and-white images are of size MxN.  The color
     depth of the image determines the numeric class of the output:
     "uint8" or "uint16" for gray and color, and "logical" for black
     and white.



Octave notices that all zeros (black) or max intensity (255) can be
represented with just a boolean matrix.  If you change the parameters of the
image away from this in any way then it will return a uint8 matrix.  For
example, I made a completely white image (all 255) with a single pixel of
value (1) in the GIMP and this is read in as MxNx3 of uint8.

I suppose this is still a problem when you next want to do something with the
MxNx3 image because now you can't set the intensity to anything besides 0 or 1
without first calling 


img = uint8 (img) * 255;




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