On Fri, Feb 26, 2010 at 5:09 PM, David MacMahon
<dav...@astro.berkeley.edu> wrote:
> As you all know by now, I'm working on Ruby bindings to PLplot. I am
> (still) almost ready for a first release. There's always "a few more
> things"! :-)
>
> I am currently working on plimagefr support, including pltr support.
> I have noticed that the documentation for plimagrfr's pltr parameter
> says that it is...
>
>> Pointer to function that defines transformation between indices in
>> array idata and the world coordinates (C only).
>
> ...but in practice it seems to call pltr with (x,y) values from (0,0)
> to (nx,ny) rather than the documented implied range of (0,0) to
> (nx-1,ny-1). I looked at the implementation of plimageslow() in src/
> plimage.c and convinced myself that the code is OK, but the docs are
> misleading.
>
> If others agree, how about clarifying the above sentence as...
>
> Pointer to function that defines transformation between indices
> (ix,iy) and world coordinates (x,y), where 0<=ix<=nx and 0<=iy<=ny (C
> only).
>
Dave,
Thank you for catching this. The coordinates in pltr_data correspond
with the corners of the data being plotted so the documentation should
be fixed. How does this sound?
Pointer to function that defines a transformation between the data
in the array <literal><parameter>idata</parameter></literal> and
world coordinates. An input coordinate of
<literal>(0, 0)</literal> corresponds to the "top-left" corner of
<literal><parameter>idata</parameter></literal> while
<literal>(nx, ny)</literal> corresponds to the "bottom-right"
corner of <literal><parameter>idata</parameter></literal>. Some
transformation functions are provided in the PLplot library:
&pltr0; for identity mapping, and &pltr1; and &pltr2; for
arbitrary mappings respectively defined by one- and
two-dimensional arrays. In addition, user-supplied routines for
the transformation can be used as well. Examples of all of these
approaches are given in <xref linkend="contour-plots-c"/>. The
transformation function should have the form given by any of
&pltr0;, &pltr1;, or &pltr2;.
The docbook code validates, so I have checked this in as revision 10857.
Hez
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