pngcairo: suggestion for additional option

[Allin C. <cot...@wf...>]

I'll float this by the list first and submit a tracker item if 
there's any support.

I would find it very useful to get a readback from gnuplot on the 
internal dimensions of a PNG file -- that is, the pixel bounds of 
the data area and also the data minima and maxima.  This is for 
generating an interactive display (much like the mousable wxt 
terminal display, but with additional features).

I may be missing something, but I don't think there's any way of 
doing this at present.

The attached patch adds a boolean "boundsfile" option to pngcairo.  
If this is activated, and if output is going to a named file, the 
driver also writes out a small auxiliary file containing the data 
mentioned above.  The aux file has the same name as the PNG file 
plus the suffix ".bounds".

For example, if you do:

set term pngcairo bounds
set output 'test.png'
plot sin(x)

you get test.png as usual, but also a file named test.png.bounds
with content

xleft=89 xright=620 ybot=37 ytop=460
xmin=-10 xmax=10 ymin=-1 ymax=1

-- 
Allin Cottrell
Department of Economics
Wake Forest University, NC