anotherObject wrote:
Sorry for not being clearer: I started off with a a 32bit tif - however, im
not sure how I can tell if it has an associated color table.
Ytrapaet,
Try running gdalinfo against the file and seeing what it reports. Including
a gdalinfo report with your email would make it much easier for us to
give a meaningful reply.
Are there both types of tifs? if so how can I convert from one to the other?
There are many types of TIFF files. TIFF supports a wide variety of color
models, pixel data types and numbers of bands.
What I do know is that when the 32bit elevation model is viewed through
ArcGIS, its default setting was on "standard deviation stretch". If I change
it to "none", it gives the correct elevation values. However, this seems to
only be a display setting;
You are correct - this is a display setting in ArcGIS and does not
reflect some fundamental nature of the file.
> when I converted the 32 to 8bit using
gdal_translate (which is the same as your example), the resulting 8bit image
did not have any stretching when I viewed it in ArcGIS. However,the
conversion did produce my8bit.tif along with my8bit.aux.xml.
Normally, when i open images in photoshop, i only plan to loose the
georeferencing information, however, it seems that when i open my8bit.tif, i
also loose the proper colors. I think this is because the color information
is stored in the .aux.xml file, but I dont know how to produce a .tif that
is any different (that does not have a .aux.xml file)
What colors do you see? Just a range of greys? Once again, you speak
of "proper colors", but I will claim there is no inherent colors involved.
Perhaps you just mean it is using a stretch or display mode that does not
meet your expectations or wishes.
Note that raw DEM data has no inherent coloring so it doesn't really mean
anything to say "so that the actual .tif grayscale colors are not
stretched
at all" in this context.
I tryed converting my 8bit.tif to 8bit.raw,
Two issues. First, when I said raw I wasn't so much speaking of a file
format, but rather of "dem data as typically provided by data providers
before being processed into special visualization form, like a shaded
relief". Second, gdal_translate does *not* decide on file format based
on file extensions, so you just produced a TIFF that happened to have
the extension .raw.
> then back to an 8 bit.tif, but i
still always end up with a .aux.xml file even with the .raw route. In other
words, any method I try, I always end up with an image that is correctly
seen my GIS programs, but incorrectly seen by photoshop. I need the correct
grayscale in photoshop so that I can interactively make new RGB color
gradients that use the elevation informaiton. I am definitely missing a
concept somewhere along the way... The way I see it, its the .aux.xml file
about color that I want embedded into the .tif instead. Is this what is
meant by "applying a color table"?
I don't know what photoshop does, and you haven't given any details on the
nature of the file (such as a gdalinfo or tiffinfo report). I am really
not sure I can help you since the issues seem mostly to be "how do I get
photoshop to display things the way I hope it will", and this isn't a
photoshop mailing list.
Best regards,
--
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I set the clouds in motion - turn up | Frank Warmerdam, [email protected]
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and watch the world go round - Rush | Geospatial Programmer for Rent
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