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J/Link MathCanvas/Graphics/Interaction

  • To: mathgroup at
  • Subject: [mg27173] J/Link MathCanvas/Graphics/Interaction
  • From: murphee <werner.schuster at>
  • Date: Fri, 9 Feb 2001 03:10:20 -0500 (EST)
  • Sender: owner-wri-mathgroup at

yo Group (especially Todd Gayley),

I am using the (magnificent) J/Link to do some interactive Mathematics;
eg: Plot a graph (eg Sine curve) and a Point, and allow the user to grab 
the Point with the
mouse and drag it along the graph;

allright, doesnt sound like much, but it's just an example to make clear 
what I
want to do;

now, the Problem is, I can use the evaluateToImage,... methods to receive a 
Bitmap (in GIF Format) of
the Plot from Mathematica,
but what I would need would be the Position of the Objects in the Plot (in 
my example: Graph, Point)
relative to the bitmap I receive from the evaluateToImage method,
so I know when the mouse is "in" one of these objects (in order to know 
when the user wants to "grab" the object);

currently, I cannot get this; I would have to guess the Position of the 
objects, but changing one Parameter in the
Plot would make this guess useless again (and the whole thing couldn't be 
done dynamically);

I haven't yet found a way in J/Link to do this, or am I just thinking in 
the wrong direction?

if there is no simple solution available in J/Link, maybe that could be 
something for J/Link 2.0 ...
since you're (you = J/Link Maintainers) at the "source" of the Production 
of the Bitmap, wouldn't it be possible
to somehow extract/preserve these parameters and allow the user to access 
from what I know, you use the psrender.exe programm to render the 
PostScript output to the GIF file;
maybe that could be a place to get that info from;

I hope someone might help me here,
Thanx in advance,
my site:
a must:
so is this:
as well as:
"... and the fact that I haven't put a gun to my mouth yet, makes me a winner!"
Al Bundy 

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