Re: Function works with number literal but not with variable

[George]

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.