[gdal-dev] Converting from 16 bit to 8 bit images (best practices?)

[Brian Case]

Jonathan

you can do scaling on individual bands.

gdal_translate -b 1 -scale 0 5000 -ot Byte -of VRT infile outfile1.vrt
gdal_translate -b 2 -scale 0 4000 -ot Byte -of VRT infile outfile2.vrt
gdal_translate -b 3 -scale 0 3000 -ot Byte -of VRT infile outfile3.vrt

gdalbuildvrt -separate output.vrt outfile1.vrt outfile2.vrt outfile3.vrt

gdal_translate -of gtiff output.vrt output.tif



for more complicated scaling you may need to hand write a vrt

http://www.gdal.org/gdal_vrttut.html

Brian

On Wed, 2011-06-08 at 19:31 -0700, Jonathan Greenberg wrote:
> Nikos and GDALers:
> 
> 
> This is CLOSE to what I'm looking to do, but I'm having a hard time
> getting it working properly.  Here's my input dataset gdalinfo dump:
> 
> 
> ***
> 
> 
> Driver: ENVI/ENVI .hdr Labelled
> Files: 10SEP10191223-M2AS-052377832030_01_P003_ps_gs_bl_tc.envi
>        10SEP10191223-M2AS-052377832030_01_P003_ps_gs_bl_tc.hdr
> Size is 42255, 51712
> Coordinate System is:
> GEOGCS["WGS 84",
>     DATUM["WGS_1984",
>         SPHEROID["WGS 84",6378137,298.257223563,
>             AUTHORITY["EPSG","7030"]],
>         TOWGS84[0,0,0,0,0,0,0],
>         AUTHORITY["EPSG","6326"]],
>     PRIMEM["Greenwich",0,
>         AUTHORITY["EPSG","8901"]],
>     UNIT["degree",0.0174532925199433,
>         AUTHORITY["EPSG","9108"]],
>     AUTHORITY["EPSG","4326"]]
> Origin = (-120.066479999999999,39.271554000000002)
> Pixel Size = (0.000004500000005,-0.000004500000005)
> Image Structure Metadata:
>   INTERLEAVE=BAND
> Corner Coordinates:
> Upper Left  (-120.0664800,  39.2715540) (120d 3'59.33"W,
> 39d16'17.59"N)
> Lower Left  (-120.0664800,  39.0388500) (120d 3'59.33"W, 39d
> 2'19.86"N)
> Upper Right (-119.8763325,  39.2715540) (119d52'34.80"W,
> 39d16'17.59"N)
> Lower Right (-119.8763325,  39.0388500) (119d52'34.80"W, 39d
> 2'19.86"N)
> Center      (-119.9714062,  39.1552020) (119d58'17.06"W, 39d
> 9'18.73"N)
> Band 1 Block=42255x1 Type=UInt16, ColorInterp=Undefined
> Band 2 Block=42255x1 Type=UInt16, ColorInterp=Undefined
> Band 3 Block=42255x1 Type=UInt16, ColorInterp=Undefined
> 
> 
> ***
> 
> 
> I need to end up with a Byte TIF image with good color balance from
> this input.  Running rgb2pct.py on this dataset just outputted a
> "blank" (grey) image.  Running gdal_translate -of GTiff -ot Byte
> -scale [min] [max] worked somewhat, but its near impossible to get
> this looking right, since the scaling I want to do differs from band
> to band (e.g. if there any way to use -scale to adjust each band
> separately)?  Alternatively, how would I get rgb2pct.py working on the
> above image correctly?  Thanks!
> 
> 
> --j
> 
> 
> 
> On Wed, Jun 8, 2011 at 4:10 PM, Nikolaos Hatzopoulos
> <nhatzop at gmail.com> wrote:
>         why you don't try rgb2pct http://www.gdal.org/rgb2pct.html?
>         
>         --Nikos Hatzopoulos
>         
>         
>         On Wed, Jun 8, 2011 at 2:20 PM, Jonathan Greenberg
>         <greenberg at ucdavis.edu> wrote:
>         
>                 
>                 Folks:
>                 
>                 
>                 I am using a piece of software which is relying on an
>                 older version of GDAL that doesn't have the "fix" to
>                 deal with > 8 bit geotiffs (it is trying to make a
>                 jpeg overlay but can't from a 16 bit image.  I think
>                 this is the issue:
>                 http://trac.osgeo.org/gdal/wiki/TIFF12BitJPEG), but
>                 when I do a straight convert (-ot Byte) the output
>                 image looks really washed out.  Any hints for getting
>                 the best quality output from a 16 bit to to an 8 bit
>                 conversion of a Geotiff?   
>                 
>                 
>                 --j
>                 
>                 -- 
>                 Jonathan A. Greenberg, PhD
>                 Assistant Project Scientist
>                 Center for Spatial Technologies and Remote Sensing
>                 (CSTARS)
>                 Department of Land, Air and Water Resources
>                 University of California, Davis
>                 One Shields Avenue
>                 Davis, CA 95616
>                 Phone: 415-763-5476
>                 AIM: jgrn307, MSN: jgrn307 at hotmail.com, Gchat: jgrn307
>                 
>                 
>                 
>                 
>                 _______________________________________________
>                 gdal-dev mailing list
>                 gdal-dev at lists.osgeo.org
>                 http://lists.osgeo.org/mailman/listinfo/gdal-dev
>         
> 
> 
> 
> -- 
> Jonathan A. Greenberg, PhD
> Assistant Project Scientist
> Center for Spatial Technologies and Remote Sensing (CSTARS)
> Department of Land, Air and Water Resources
> University of California, Davis
> One Shields Avenue
> Davis, CA 95616
> Phone: 415-763-5476
> AIM: jgrn307, MSN: jgrn307 at hotmail.com, Gchat: jgrn307
> 
> 
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