Re: [Plplot-devel] plgetpos transformation (was valgrind)

[Maurice L. <mj...@ga...>]

Alan W. Irwin writes:
 > It would be a big help if one of you could give me a definition of absolute,
 > relative, and normalized coordinates.  Perhaps for completeness you should
 > also include world coordinates, but I think I understand what those are.

I could've sworn I went through and documented these some time ago in response
to a similar request.  Can't find any trace of it now though, sigh.  Since I
get confused too I had to go through the code to refresh my memory, and this
is what I came up with:

    physical coordinates and device coordinates

are the same thing.  The "pixel" addresses in device space, typically 0 up to
some large value in each coordinate.

    absolute coordinates

are page coordinates in mm.  Only strictly accurate for fixed-page-size output
devices.

    relative device coordinates and normalized device coordinates

are the same same thing -- position in a [0.,1.] by [0.,1.] representation of
the page.

-- 
Maurice LeBrun    mj...@ga...