- Tong - on wrote...
| Hi Anthony,
|
| On http://www.imagemagick.org/Usage/photos/, you have a minor
| underexposure example.
|
| Before going into -sigmoidal-contrast operator, maybe it is a good
| idea to first discuss convert's built-in -normalize operator that
| is similar to GIMP's "auto-levels" or "normalize" feature that
| stretch pixel values from darkest to brightest.
|
| convert minor.jpg -normalize minor.normalized.jpg
|
| Also, maybe you'd like to through in how IM can also create the
| three-color histogram out of it:
|
| convert minor.jpg histogram:- | convert - minor.histogram.jpg
|
| Looking at the histogram, I think it may explain what you wrote:
|
| __________________________
| Sigmoidal contrast brightening tends to de-emphasize the red end
| of the spectrum. You may end up having to select a parameter that
| results in the most natural flesh tones, rather than the
| brightness level you really want.
| __________________________
|
Actually I did not write it. It was contributed. If you like to edit
the page, you are welcome to do so, and send me the results.
Photo processing is NOT a strong point of mine.
Anthony Thyssen ( System Programmer ) <[EMAIL PROTECTED]>
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Graffito in a MIT lavatory...
Heisenberg might have been here
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Anthony's Home is his Castle http://www.cit.gu.edu.au/~anthony/
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