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

[Jonathan Greenberg]

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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.osgeo.org/pipermail/gdal-dev/attachments/20110608/698a77eb/attachment.html