Martin,<br><br>You could scale the actual values into 'float' values between 0 and 255. This way you can still have the resolution. Conversion to 8-bit will be easier.<br><br>Use GDALRasterBand::GetOffset() and GDALRasterBand::GetScale() along with GDALRasterBand::SetOffset() and GDALRasterBand::SetScale()<br>
Docs at <a href="http://gdal.org/classGDALRasterBand.html">http://gdal.org/classGDALRasterBand.html</a> describe how to use these.<br><br><div class="gmail_quote">On Tue, Aug 10, 2010 at 4:32 PM, Andrew Brooks <span dir="ltr"><<a href="mailto:arb@sat.dundee.ac.uk">arb@sat.dundee.ac.uk</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div class="im">On Tue, 10 Aug 2010 11:46:00 +0100, Martin Raspaud <<a href="mailto:martin.raspaud@smhi.se" target="_blank">martin.raspaud@smhi.se</a>> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
We have a satellite image in black and white, which show IR brightness<br>
temperatures. The data is scaled between 0 and 255 for viewing, and this is<br>
packed in a geotiff file<br>
<br>
Now some users would like to have the true value of the brightness temperature<br>
embedded in the file also.<br>
</blockquote>
<br></div>
Maybe you can simulate something close by putting a scale and offset (slope<br>
and intercept) into the geotiff so you still display 8-bit values but a decent<br>
image viewer will also calculate the true values and give a pixel readout of<br>
the true value under the cursor. I say simulate because 8 bits may not give<br>
sufficient resolution.<br><font color="#888888">
<br>
Andrew</font><div class="im"><br>
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</div></div></blockquote></div><br><br clear="all"><br>-- <br>Best regards,<br>Chaitanya kumar CH.<br>/tʃaɪθənjə/ /kʊmɑr/ <br>+91-9494447584<br>17.2416N 80.1426E<br>