Global Mapper v26.0

loading only some part of large map files

myh
myh Global Mapper User
edited August 2008 in SDK
Hi all
I am a newbie on global mappers.

is possible loading only some part of large map files (such as *.ecw) ?
if answer is OK , How (in vc++6) ?

tanks a lot .

Comments

  • global_mapper
    global_mapper Administrator
    edited August 2008
    You can choose what portion of a map to display simply by providing an appropriate bounding box to the GM_DrawLayerList function. If you pass NULL for the bounding box then all loaded data will be displayed, so you'll want to actually setup a boundign box with your area of interest. The C++ sample application included with the SDK demonstrates how to do this to pan and zoom the map.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • myh
    myh Global Mapper User
    edited August 2008
    ok
    but i want actually "Load" one portion of Large files .
    i think this solution "Display" one portion afetr loading hole file !

    thanks a lot
  • global_mapper
    global_mapper Administrator
    edited August 2008
    There is not a way to just load a particular portion of a file, but since Global Mapper doesn't read an entire file into memory in most cases (like ECW), there really wouldn't be any point in loading just a portion of a file anyway as there really wouldn't be any difference.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • myh
    myh Global Mapper User
    edited August 2008
    Tanks Mike

    Can we found that Global Mapper do this with which types of Map Files ?
    or Know when do this ?
    or We force it to do this ? (according to the memory size or other thinks ... )
  • global_mapper
    global_mapper Administrator
    edited August 2008
    There really isn't any support for loading just parts of a map for any formats. For pretty much any raster format Global Mapper will read from disk as needed (with some in-memory caching) rather than keep the entire thing in memory. For those formats that don't support something like that (i.e. JPG, PNG, etc.), large images will be decompressed to disk and read on-demand from a temporary file to avoid excessive memory usage.

    So for the most part Global Mapper will automatically handle things to keep memory usage under control. You just need to control which part of the loaded map that you draw.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com

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