[Octave-bug-tracker] [bug #49137] some grayscale images are displayed badly

[Carnë Draug]

Follow-up Comment #2, bug #49137 (project octave):

This are two different issues. One of them is a bug:

1. call imshow with a filename

This is a bug, and the problem ins that imshow does:


  ## Get the image.
  if (ischar (im))
    [im, map] = imread (im);
    indexed = true;
    colormap (map);
  endif


but that's now how imread works. If the image is not indexed, then map is
empty. This should be something like:


  ## Get the image.
  if (ischar (im))
    [im, map] = imread (im);
    if (isempty (map))
      indexed = false;
    else
      indexed = true;
      colormap (map);
    endif
  endif


2. call image instead of imshow.

The call to subplot is irrelavant here. I don't think this is a bug. image()
is not the function to display an image, it is meant to display a matrix as if
it was a figure and needs a colormap. Because there is no colormap, it uses
the default colormap which has only 64 indices. Because all values are higher
than 64, then all pixels show up "saturated" (yellow in 4.1, red in 4.0)

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