Hello Hao
I'm moving a question on the public list since I believe that some other
peoples know better than me.
About how to get the geographic bounding box from a GeoTIFF file: I
didn't saw tags specifically for this purpose in GeoTIFF, but this can
be computed indirectly. First we need to build the mathematical function
that convert pixel coordinates to geographic or projected coordinates.
Then we can use that function for converting the raster bounds (in pixel
coordinates) to geographic or projected envelope.
For creating the mathematical function as an "affine transform", we need
one of the following tags [1]:
* ModelPixelScaleTag
* ModelTiepointTag
or
* ModelTransformationTag
What are the tags that you have in your GeoTIFF file? For starting, we
would focus on what you have.
Martin
[1] http://www.remotesensing.org/geotiff/spec/geotiff2.7.html#2.7
