[gdal-dev] Applying colour/contrast corrections to geotiffs
penorman at mac.com
Mon Mar 11 10:55:55 PDT 2013
I am generating a geotiff from a WMS source. I can do so from either PNG
requests or JPEG requests. The PNG requests have better contrast but are
4x-5x as slow.
I would like to compare the PNG and JPEG request results for a
representative area and develop a contrast correction which I can apply to
the JPEG request result to make it look like the PNG request result, but I
am not certain how to do this. I can get histograms and stats with gdalinfo.
I was thinking perhaps developing a LUT correction which I could then apply,
but I'm not sure how to match the images or apply the correction.
Other potentially relevant information
- The total image size is going to be 350GB-500GB, in a few slices
- The WMS server owners are okay with me scraping this, but won't give me
the original imagery file
- I will be eventually compressing the imagery as JPEG in TIFF
- The result will be used by mapserver, then sliced and served as TMS images
by mapproxy. If all else fails I can apply a LUT in mapserver.
- Screenshots of the jpeg request results vs. png request results are at
http://took.paulnorman.ca/images/databc_differences.png. The differences are
minimal, but I'd like to do this right
I'm after any suggestions for how to derive the adjustments needed as well
as how to apply them.
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