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May 2008
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2008.05.18 08:59 "Re: 32 bit samples", by Andrey Kiselev
Garry, On Sat, May 17, 2008 at 09:34:25AM -0700, Garry Petrie wrote: > This web app can produce geotiff files containing digital elevation > data for any place in the world using data from the space shuttle SAR > mission. The format of the tiff portion of the file contains 32 bit > samples, not sure if they are longs or short floats. There is a special tag for that, called "SampleFormat". It denotes the dat type. > Using libtiff I get the message about not being able to handle 32bit > samples from getimage. I know the web site produces good image files, > as I have been able to view the files with AdobePS. I peaked at alpha > 4.0 and it seems to have the same critical code as 3.8.2. Are there > great obstacles in enabling this function? I am willing to spend some > time with the code, but I don't want to become an expert. Uor mistake is that you are trying to use RGBA interface of libtiff which can be used for simple images only (1-3 channels, integers, <8 bit in depth). No way to read complex datasets with this API. You should either use a low-level libtiff API or some spicialized software which hides this low-level details from you. GDAL (http://www.gdal.org) will do it for you. Also take a look on OpenEV viewer, because Photoshop is not a suitable tool to deal with georeferenced images. Best regards, Andrey -- Andrey V. Kiselev ICQ# 26871517