[gdal-dev] Newbee - pointers needed

[Even Rouault]

Le Wednesday 08 July 2009 23:17:07 Smart, Gary, vous avez écrit :
> OK - I have been coding c++ raster image display systems on Linux for
> years now and long ago developed our own raster map display system based
> on CADRG/ASRP files.  Our system effectively maps a huge raster image
> space around the world and stitches together tiles from raster map files
> as the user moves his view around the globe.
>
>
>
> I wish to investigate and perhaps use the GDAL as a more generic map
> reader.  However, having parsed some tutorial information and a few
> example cpp files, I am none the wiser on how it works.
>
>
>
> I need some pointers to some generic information/example c++ code which
> can provide me with answers to the following sorts of questions?
>
>
>
> 1)       How to register map files with the GDAL.

You don't "register" maps with GDAL. You open datasets with GDALOpen()

>
> 2)       How to request areas of map to populate my raster output space
> (and how do I ensure only compatible map sources are brought together)

GDALRasterIO() / GDALDatasetRasterIO() will fetch data from regions expressed 
in pixel space of the raster. You can use the affine transform matrix 
(geotransform) given by GDALGetGeoTransform() to convert between pixel and 
geo spaces.

Not sure what you mean by "compatible map sources".

>
> 3)       Are tiles of raster map extracted by specifying geo-space
> boundaries?

See above

>
> 4)       And a million more questions...
>
>

My understanding of your needs is that MapServer could also be worth 
exploring.

>
> Can someone point me to some documentation which can put me in the
> picture as to how a user might use the GDAL to display maps on the
> screen (the fine details of actual rendering are not required - I just
> need to know how to get the information from the input files in a common
> display format) and perhaps some example code (e.g. to extract
> rasterized tiles of a specific geo-area)?
>
>
>
> Just some pointers for some reading are all that I'm after really.
>
>
>
> Gary