[Liblas-devel] Overriding a Reader's header

[Howard Butler]

Mateusz,

I'd like to propose an API addition to LASHeader to provide a  
constructor that overrides the file's header.  I have a single,  
practical use case for this, but users might have others.  As part of  
the reader/writer reprojection machinery, an important issue crops up  
-- what to do about the data's scale.  For example, if we set input  
coordinate system to UTM and have a X/Y scale of 0.001 and then try to  
reproject this to DD, leaving our scale at 0.001 is going to trim off  
way too much.  We really need to set the scale to something like  
0.00000001, but we can't do that in any meaningful way because the  
scale comes from our as-read-from-the-file header.

I propose that we provide a

LASReader(std::istream& ifs, LASHeader& header)

constructor, and if this constructor is used, this header is used to  
describe the data except for the following condition... we respect the  
dataoffset as it exists in the file (why it isn't const).  This will  
allow a user to override things like the coordinate system, scales,  
dates, etc but still allow the file to be read.

Make sense?

Howard

PS I'll also develop C API and Python API to use this.