[cad-linux] Re: Autocad

  • From: AJBIBB@xxxxxxx
  • To: cad-linux@xxxxxxxxxxxxx
  • Date: Thu, 24 Jul 2003 19:06:45 EDT

David,

Sorry about the e-mail block.  Use buyer242299@xxxxxxx if you want to write 
to me direct.

As I am sure you have discovered in your research, the dxf file can be though 
of as 
a key list (in lisp it is called an association list).  For instance in text 
entities code 10 is associated with a real number that represents an x 
coordinate, 20 is a Y coordinate and 30 is a Z coordinate.  Code 8 typically 
refers 
to the layer the entity is on, and as you may have guessed code 1 refers to the 
actual text.  DXF codes can have different meanings depending on what entity 
they are associated with, but as you play with them you will notice a certain 
consistency between various entities.  The coordinates are relative to the 
point 0,0,0 which can be located anywhere in your drawing.   

The puzzle that you need to solve about finding the text in the DXF file is 
the same one that would need to be solved if someone (maybe me) were to write 
you a program to extract this data.  I was really hoping that the text you were 
looking for was a block attribute or at least had some distinctive sequence 
of characters that could be searched for.  The insertion points (code 10,20,30) 
in the two examples you sent were wildly different, so I doubt finding all 
text between certain coordinate bounds will work.  Your best bet may be to 
search for all code 1 entities that have 5 and only 5 characters.  This should 
return everything you need and at worst it will return some spurious values 
that 
will just need to be deleted.

Andy

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