| Re: advanced image enhancement [message #32480] |
Mon, 14 October 2002 09:23  |
David Oesch
Messages: 31
Registered: October 2000
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thany you guys...<br>
it works fine!<br>
<br>
D<br>
<br>
Liam E. Gumley wrote:<br>
<blockquote type="cite" cite="mid:3DAAF70C.1367D29F@ssec.wisc.edu">
<pre wrap="">"Liam E. Gumley" wrote:<br></pre>
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<pre wrap="">David Oesch wrote:<br></pre>
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<pre wrap="">Is there any other possibility to enhance the content of an bytarr<br>image? I tried BYTSCL and HIST_EQUAL, but ?m actually lokking for a Root<br>enhancement, also known as a logarithmic transform, which particularly<br>effective with images whose grey level distribution exhibits right<br>skewness. The root enhancement stretches the dynamic range of the low<br>end of the image while compressing its high end. It tends to lend an<br> overall brightening to the resultant image.Has anyone implemented such<br>an enhancement in IDL?<br></pre>
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<pre wrap="">Here's a simple example of a square root enhancement:<br><br>a = dist(256)<br>scale = (a - min(a)) / (max(a) - min(a))<br>tv, byte(255.0 * scale) ; linear enhancement<br>tv, byte(255.0 * sqrt(scale)) ; square root enhancement<br><br>For extra credit, turn this into a function that accepts MIN, MAX,<br>BOTTOM, and NCOLORS keywords.<br></pre>
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<pre wrap=""><!----><br>I should have check the User Libraries first:<br><br><a class="moz-txt-link-freetext" href=" http://www.astro.washington.edu/deutsch-bin/getpro/library13 .html?SQRTSCL"> http://www.astro.washington.edu/deutsch-bin/getpro/library13 .html?SQRTSCL</a><br><br>Cheers,<br>Liam.<br>Practical IDL Programming<br><a class="moz-txt-link-freetext" href="http://www.gumley.com/">http://www.gumley.com/</a><br></pre>
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<pre class="moz-signature" cols="$mailwrapcol">--
_________________________________________________
David Oesch - Remote Sensing Research Group
Department of Geography
University of Bern Tel : +41 (0)31 631 8020
Hallerstr. 12 Fax : +49 (0)89 2443 43780
CH - 3012 Bern Mail: <a class="moz-txt-link-abbreviated" href="mailto:David.Oesch@giub.unibe.ch">David.Oesch@giub.unibe.ch</a>
Switzerland <a class="moz-txt-link-freetext" href="http://www.giub.unibe.ch/remsen">http://www.giub.unibe.ch/remsen</a>
Remote Sensing is...
Staying as far away from the problem as possible.
- G. Archer, World Bank
_________________________________________________
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| Re: advanced image enhancement [message #32481 is a reply to message #32480] |
Mon, 14 October 2002 09:51  |
Liam E. Gumley
Messages: 378
Registered: January 2000
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Senior Member |
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David Oesch wrote:
> Is there any other possibility to enhance the content of an bytarr
> image? I tried BYTSCL and HIST_EQUAL, but ?m actually lokking for a Root
> enhancement, also known as a logarithmic transform, which particularly
> effective with images whose grey level distribution exhibits right
> skewness. The root enhancement stretches the dynamic range of the low
> end of the image while compressing its high end. It tends to lend an
> overall brightening to the resultant image.Has anyone implemented such
> an enhancement in IDL?
Here's a simple example of a square root enhancement:
a = dist(256)
scale = (a - min(a)) / (max(a) - min(a))
tv, byte(255.0 * scale) ; linear enhancement
tv, byte(255.0 * sqrt(scale)) ; square root enhancement
For extra credit, turn this into a function that accepts MIN, MAX,
BOTTOM, and NCOLORS keywords.
Cheers,
Liam.
Practical IDL Programming
http://www.gumley.com/
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| Re: advanced image enhancement [message #32482 is a reply to message #32481] |
Mon, 14 October 2002 09:55 |
Liam E. Gumley
Messages: 378
Registered: January 2000
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Senior Member |
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"Liam E. Gumley" wrote:
>
> David Oesch wrote:
>> Is there any other possibility to enhance the content of an bytarr
>> image? I tried BYTSCL and HIST_EQUAL, but ?m actually lokking for a Root
>> enhancement, also known as a logarithmic transform, which particularly
>> effective with images whose grey level distribution exhibits right
>> skewness. The root enhancement stretches the dynamic range of the low
>> end of the image while compressing its high end. It tends to lend an
>> overall brightening to the resultant image.Has anyone implemented such
>> an enhancement in IDL?
>
> Here's a simple example of a square root enhancement:
>
> a = dist(256)
> scale = (a - min(a)) / (max(a) - min(a))
> tv, byte(255.0 * scale) ; linear enhancement
> tv, byte(255.0 * sqrt(scale)) ; square root enhancement
>
> For extra credit, turn this into a function that accepts MIN, MAX,
> BOTTOM, and NCOLORS keywords.
I should have check the User Libraries first:
http://www.astro.washington.edu/deutsch-bin/getpro/library13 .html?SQRTSCL
Cheers,
Liam.
Practical IDL Programming
http://www.gumley.com/
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| Re: advanced image enhancement [message #32483 is a reply to message #32480] |
Mon, 14 October 2002 08:30 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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David Oesch (oesch@giub.unibe.ch) writes:
> Is there any other possibility to enhance the content of an bytarr
> image? I tried BYTSCL and HIST_EQUAL, but ?m actually lokking for a Root
> enhancement, also known as a logarithmic transform, which particularly
> effective with images whose grey level distribution exhibits right
> skewness. The root enhancement stretches the dynamic range of the low
> end of the image while compressing its high end. It tends to lend an
> overall brightening to the resultant image.Has anyone implemented such
> an enhancement in IDL?
I don't have this particular algorithm coded up, but
you might find XSTRETCH handy for enhancing particular
sections of the image:
http://www.dfanning.com/programs/xstretch.pro
At the very least, it might give you some ideas.
Cheers,
David
--
David W. Fanning, Ph.D.
Fanning Software Consulting, Inc.
Phone: 970-221-0438, E-mail: david@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155
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