[IPOL discuss] computing and displaying contours

[Jean-Michel Morel]

José Luis,

This sounds great. Pascal Monasse and Adina Ciomaga also need it "urgently".

Best,
JM

José Luis Lisani a écrit :
> Dear all,
> 
> I have a C++ code for computing and drawing level lines from a 
> bilinearly interpolated
> version of the image:
> http://www.cmla.ens-cachan.fr/fileadmin/Documentation/Prepublications/2001/CMLA2001-16.ps.gz 
> 
> 
> I had planned to publish the code at IPOL, on an undefined date.
> But, if there is a real need for the code I can accelerate my plans. I 
> think I can
> have something running in a month or so.
> Once the code has been certified by IPOL it could become part of the tools
> made available to the rest of authors.
> 
> Best regards,
> José Luis
> 
> 
> El 15/03/2011 17:38, Juan Cardelino escribió:
>> Dear all,
>>            I remember that we discussed the topic of visualization in
>> the september meeting. I'm not sure if you have advanced in that
>> direction in January, if that's the case, please update me.
>> So far I contributed in demos for me and for people that were also in
>> IPOL. I'm facing the first case of helping a non-member of the crew,
>> and I have some doubts about were to draw the line of what's
>> responsibility of the author and what's the task of the editor.
>>
>> The case is the following: the author is Mauricio Delbracio and his
>> algorithm that estimates a PSF, so the output are regular samples of a
>> 2D function. When thinking about visualization, the wanted to display
>> the level lines of that function. This involves a couple of tasks:
>>
>> 1) actually computing the contours:
>> a) I think this should be done by the author
>> b) however, it won't hurt to have a handful of simple functions at
>> hand, to provide the authors. Maybe we can just reuse the code done by
>> the first autor interested in doing the task.
>> c) I think about many cases in which we could be interested in
>> computing/showing level lines, so maybe the definition of an interface
>> (how to specify the points of the contour) could be useful.
>> d) I google'd for a bit to find any clean C implementation of the
>> marching squares algorithm but without luck. do you know/have any
>> piece of C code to compute contours? I know implementations in ITK and
>> VTK, but that's out of the question. I find sad that there is no
>> reference implementation of such well-know and established algorithms.
>>
>> 2) drawing the contours on the web page:
>> a) the first ugly way to do this is to just ask the author for an
>> image with white pixels over a black background. I think this is
>> efortless but poses many problems (low resolution, no scaling, etc).
>> b) Ask the user to draw in a vectorial format like eps or svg. As far
>> as I know, svg support varies too much across browsers. (correct me
>> please if I'm wrong)
>> c) ask the author for a description of the curve as in 1c) and render
>> it using javascript of whatever we like. Here we need a precise
>> definition of the curve, as I guess we don't want to recode that part
>> for each new demo.
>> d) I think in general this should be our concern, not the authors.
>>
>> Personally, I would go for the svg, but sadly technology is not on our 
>> side yet.
>> What do you think? Is there any hack to make an svg look the same in
>> different browsers?
>>
>> Thanks in advance.
>> Best regards,
>>                    Juan
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