Re: zoom into float image data?

[davidf(at)dfanning.com (David Fanning)]

Andrew (amacphee@my-deja.com) writes:

> I've got arrays of float where the interesting data lies in a small
> range. For example, the raw data ranges from -123.45 to 5678.9,
> whilst the interesting stuff lies between 123.4 and 125.6. For each set
> the interesting data is not necesserily in the same range.
> 
> I'm trying to write something that:
> 1) displays the image bytescaled;
> 2) uses xloadct to stretch the colour table to home in on the
> interesting data;
> 3) re-bytescales the data with new min and max values determined from
> the scaling of the colour table.
> 4) Iterate 3 and 4 until I've zoomed in on the interesting data.
> 
> I thought I could use the numbers on the stretch bars in xloadct as
> feedback to re-bytescale my input data, but these numbers aren't
> returned by xloadct. I then thought I could use tvlct to read the rgb
> values after stretching, then use e.g. min(where(r>0)) and
> max(where(r<255)) to find how much I had stretched the table. However, I
> expect I would need to do the same for green and blue and I can't see
> then how this would correspond to the 'stretch' numbers in xloadct if
> the colour table wasn't linear in all three colours.
> 
> Then I wondered if anyone else had gone around this loop and maybe had
> come up with a far slicker, tried and trusted solution :-)

I think my XStretch program is made to order. :-)

   http://www.dfanning.com/programs/xstretch.pro

You will need XColors too, if you want to change color
tables:

   http://www.dfanning.com/programs/xcolors.pro

Cheers,

David 

-- 
David Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438 E-Mail: davidf@dfanning.com
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