Re: Function works with number literal but not with variable

[John W. Eaton]

On 16-Dec-2009, George wrote:

| On Wed, Dec 16, 2009 at 11:36 AM, George <address@hidden> wrote:
| > imshow doesn't work if an image contains both positive and negative
| > values. So I tried to write a wrapper for imshow that will scale the
| > image so that all the elements are positive. So I call imshow from
| > within my function. The problem is that it doesn't work if I pass the
| > limits from variables, but it works if I type them as numbers. So this
| > code doesn't work:
| >
| >        minVal = min(min(image));
| >        maxVal = max(max(image));
| >        [rows, columns] = size(image);
| >        normalized = image - ones(rows,columns) * (minVal);
| >        minVal = min(min(normalized));
| >        maxVal = max(max(normalized)); % for my test image this is 44.2, I
| > can see it if I remove the semicolon
| >        imshow(normalized, [0, maxVal]);
| >
| > But it works if I change the last line to this:
| >
| >        imshow(normalized, [0, 44.2]);
| >
| > Two questions here:
| >
| > Why does this happen?
| > Why doesn't imshow work with images that have both positive and negative 
values?
| 
| I found that the problem was that my image was of type 'single'. If I
| convert it to 'double' imshow works. Is this a bug? I think so.

If you think you've found a bug, then please send a complete bug
report to the address@hidden list.  Please see
http://www.octave.org/bugs.html to see what information you should
include in your report.  At the very least, you should include the
version of Octave you are using, a complete example that can be used
to duplicate the problem, what you see when running your example, and
what you expect to see.

jwe