[pdal] How to get las header info?

[Mateusz Loskot]

On Tue, 5 Jul 2022 at 19:06, Peder Axensten <Peder.Axensten at slu.se> wrote:
>
> I tried that too. :-)
> I tried the following, inspired by code on https://pdal.io/api/transition/index.html:
>
>     pdal::LasHeader get_header( const std::filesystem::path & path_ ) {
>         pdal::Option              las_opt( "filename", path_.native() );
>         pdal::Options             las_opts;
>         las_opts.add( las_opt );
>
>         pdal::PointTable          table;
>         pdal::LasReader           las_reader;
>         las_reader.setOptions( las_opts );
>         las_reader.prepare( table );
>
>         pdal::PointViewSet        point_view_set = las_reader.execute( table );
>         pdal::PointViewPtr        point_view = *point_view_set.begin();
>         pdal::Dimension::IdList   dims = point_view->dims();
>         return las_reader.header();

You observe garbage header because it actually is destroyed at exit
from get_header.
You must keep LasReader object alive for as long as you refer to its
LasHeader object.
The LasHeader is NOT a value type, but a thin 'view' over internal object.

The bug in your code is somewhat equivalent to this

auto foo()
{
    std::vector<int> v;
    return v.begin();
}

Best regards,
-- 
Mateusz Loskot, http://mateusz.loskot.net