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#125 Make clickable graphics possible
First of all let me say that I'm impressed by the
changes done from gnuplot 3 to 4. Especially the mouse
control in the plot window is very much appreciated.
I'd like to generate graphics for a web page with
gnuplot. For that I'd need some elements (eg. axis
ticks) clickable, so that I can "zoom" or rearrange the
data.
The obvious target for that is SVG, as that includes
the possibility to define links; but if that could be
done for PNG too (perhaps with a new command like
"export click maps") I'd be very glad.
Thank you!
Regards,
Phil
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I think there are external tools for making clickable web
graphic maps.
You cantry yourself to work out a clickable interface -- use
the "bind" command to define you own hotkeys on an
interactive terminal and produce an appropriate label or
whatever you need to paste in the final output file.
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Well, the problem with external tools is that they basically
have to derive the "clickable" positions somehow.
Eg. take a simple graph - some points over some time
interval, say weeks.
If I now want to make the weeks (the labels on the x-axis)
clickable and show details for this week - how does an
external program find out which week is where?
Given SVG output it might be possible - with good algorithms
to distinguish y-axis labels from x-axis labels from other
labels ....
With an PNG that leads to an OCR run (on possibly 90° turned
strings) or a complete re-engineering of the dimension,
orientation, and positioning of the plot - at which point
the program itself could simply put out some SVG statements ...
What I'd like is to have some syntax to specify URLs for
single elements, and, possibly, a terminal-related call for
exporting a CMAP or whatever (for the cases where a bitmap
is exported. SVG can have the links inline).
Regards,
Phil
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The discussion should separate into these parts:
- clickable positions, driven from an external program --
easy (like ginput function in Octave/Matlab)
- png clickable maps in html -- easy, there are external
tools for this
- svg interactive maps: you seem to know a lot about this,
so you can probably find an appropriate implementation; you
can use some postprocessing by javascript or php from what
gnuplot returns
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1) I don't know about ginput and Matlab. Could you please
explain what you mean here?
2) Making maps for eg PNG is easy - *if you know the
coordinates*.
And a simple script piping into gnuplot doesn't.
3) Postprocessing a SVG would be possible (but not nice), if
there was an easy way to distinguish the various strings and
elements.
Currently all I get from gnuplot is a SVG with lots of
<g transform="translate(316,466)"
style="..."><text>...</text>.
There's no information if that's on the x-axis, the y-axis,
a custom label, a data label, legend or whatever.
It would be enough (but still not the Best Way) to include
specific IDs in the SVG (if that's at all possible; I know
SVG from opening generated files :-):
<g id="axis-x-0" ...>
<g id="axis-x-1" ...>
<g id="axis-x-2" ...>
<g id="axis-y-0" ...>
<g id="axis-y-1" ...>
<g id="axis-y-2" ...>
<g id="custom-0" ...>
<g id="legend-0" ...>
and so on.
Then a script could (with reasonable expense) parse the SVG
and change it.
Of course, in the long run I'd find it best if there was
something like
set format x "week %d" URL "http://server/url?data=%d"
which would output automatically for svg, ps, and pdf, and
which had another command for outputting maps, like graphviz.
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1) A program (Octave, python, your C, ...) can interact with
gnuplot through a pipe, and it can also read mouse
coordinates. See gnuplot web page for more info (section
"bidirectional communication").
2) You know the coordinates if it's you who are generating a
map for a specified xrange and yrange.
3) You can put your own "set label" at some specific
positions wherefrom you can extract coordinates.
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Sorry, I do not seem to make myself clear.
But I'll try again. (Thanks for your patience !)
I have a webpage, with cgi/php/whatever on the server.
The backend generates a graphic (bugs per week, if you
like), and displays it on the browser of the user.
The user shall now be able to click on the data-points
and/or the x-axis-labels to "zoom" a week and show details.
Making the graph is easy. Just do a "SELECT count(id) FROM
bugs ORDER BY week;", put that with a bit of text header on
STDIN of gnuplot, and the graphic is finished.
Now I can display something - but I don't know where the
points and labels on the graphic are.
To know that I'd have to calculate positions from size of
graphic, fontsize, minimum and maximum values of the axes,
etc., and when that is done I wouldn't need gnuplot anymore,
I'd already have done the graph myself.
So I'd just put a line of header more, eg.
set format x "week %d" URL "http://server/url?data=%d"
and be done, as the URL would automatically be used in SVG,
and for PNG/GIF there could be another command to export the
map.
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@P.Marek: A good part of the confusion between is caused by
terminology differences.
To put what you want in a more gnuplot-like context, what
you want is sort-of an implementation of the mouse
interaction interface for file output terminal drivers.
I.e. similar to the feature that lets the GUI terminal
drivers interactively display the data coordinates of points
as the mouse is moved around, the file output drivers could
export the same information (basically xleft, xright, ...)
to a separate file, or as comment records in in their
ordinary output files.
There's been a patch proposing something like this for GIF,
long ago, but I rejected that, IIRC because its
implementation was too much at odds with gnuplot's internal
structure. It was called 'coordinate transforms information
export' or somehting like that. Good luck finding it in the
tracker pages...
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Half of this request is, I think, satisfied by recent additions to CVS that export the axis coordinate mapping of the current plot on the current terminal to GPVAL_TERM_XMIN GPVAL_TERM_XMAX and so on.
The other half is at least potentially addressed by Patch #1866413 "Demarcate plots to allow post-processing". Check out the sample SVG plot with live links attached to individual plot elements.
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