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

Nikolaos Hatzopoulos nhatzop at gmail.com
Fri Jun 10 12:49:46 EDT 2011


Rapid response for true color has this:

;- Rapid Response default enhancement: 0,0, 30,110, 60,160, 120,210,
190,240, 255,255
x = byte([0,  30,  60, 120, 190, 255])
y = byte([0, 110, 160, 210, 240, 255])

;- Rapid Response cloud enhancement: 0,0, 25,90, 55,140, 100,175, 255,255
if keyword_set(cloud) then begin
  x = byte([0, 25,  55, 100, 255])
  y = byte([0, 90, 140, 175, 255])
endif


how it can be programmed in gdal language?

--Nikos

On Thu, Jun 9, 2011 at 8:42 PM, Brian Case <rush at winkey.org> wrote:

> Nikos
>
> 143, and 721
>
> Brian
>
> On Thu, 2011-06-09 at 16:49 -0700, Nikolaos Hatzopoulos wrote:
> > for modis truecolor images?
> >
> > --Nikos
> >
> > On Thu, Jun 9, 2011 at 4:44 PM, Brian Case <rush at winkey.org> wrote:
> >         Jonathan
> >
> >         I don't know about worldview, but with modis I wound up using
> >         multiple
> >         ranges
> >
> >         0:0,750:110,1500:160,3000:210,4750:240,6375:255
> >
> >         see <lut>  in the vrt tutorial
> >
> >         Brian
> >
> >
> >
> >
> >
> >
> >
> >         On Thu, 2011-06-09 at 12:39 -0700, Jonathan Greenberg wrote:
> >         > Brian:
> >         >
> >         >
> >         > Thanks!  Great solution, definitely saved me some time.  The
> >         main
> >         > issue (in terms of doing this entirely within GDAL) is
> >         getting the
> >         > right scaling to make the image look good.  I was able to
> >         figure out
> >         > the correct scale range within ENVI, and then apply the
> >         scales as you
> >         > suggested below.  Nikos' suggestion to use rgb2pct makes me
> >         wonder if
> >         > there is some way to figure out the optimal scale (which,
> >         AFAIK, is
> >         > part of how rgb2pct is functioning) to apply to this image.
> >         >
> >         >
> >         > Incidentally, what I'm trying to do is load Worldview-2 data
> >         onto an
> >         > iPad 2 for use with the GISRoam mobile mapping app.
> >          Worldview-2 is
> >         > 16-bit per band, 8 band data, with a very high dynamic range
> >         (we have
> >         > snow in our image, so we have lots of VERY bright pixels
> >         which throw
> >         > off the adjustment if using -scale without any parameters).
> >          99%
> >         > (100%?) of mobile mapping applications need 3-band data,
> >         usually with
> >         > only 8 bits per band.
> >         >
> >         >
> >         > Pushing forward, but if someone knows how to figure out an
> >         optimal set
> >         > of scale values to use within GDAL, please post the
> >         solution.
> >         >
> >         >
> >         > --j
> >         >
> >         > On Wed, Jun 8, 2011 at 9:45 PM, Brian Case <rush at winkey.org>
> >         wrote:
> >         >         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
> >         >         >
> >         >         >
> >         >         > _______________________________________________
> >         >         > 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
> >         >
> >         >
> >         > _______________________________________________
> >         > gdal-dev mailing list
> >         > gdal-dev at lists.osgeo.org
> >         > http://lists.osgeo.org/mailman/listinfo/gdal-dev
> >
> >
> >         _______________________________________________
> >         gdal-dev mailing list
> >         gdal-dev at lists.osgeo.org
> >         http://lists.osgeo.org/mailman/listinfo/gdal-dev
> >
> >
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.osgeo.org/pipermail/gdal-dev/attachments/20110610/d71c345f/attachment-0001.html


More information about the gdal-dev mailing list