Re: [Scilab-users] density in a graph

[Jean-Philippe Grivet]

P M, Claus, Antoine, Christophe; Federico:

Thank you  all fior your multifaceted and interesting suggestions. A 
special mention to Christophe: the pages on the SVG format are extremely 
clear; in my opinion, they deserve a wide audience and should be 
translated in English.


I now understand that I should have described my ultimate goal, even 
though it is somewhat complicated.. My aim is to emulate image 
reconstruction in X-ray tomography. In the simplest reconstruction 
algorithm,  back projection, one must darken the image plane 
proportional to the value  of  a "projection" of the object, for each 
projection direction (at least 128 in all). These "darkenings"  must add 
everywhere in the image plane. A sketch of this process is shown in the 
attached figure.


I have found two other possible approaches. In thee book by Michel 
Goossens et al (the Latex graphics companion) there appears (pp 257-258) 
a Latex program that emulates transparency. To use this , I would have 
to read into pstricks the coordinates of the various rectangles, which 
seems possible. Moreover, I have read that PDF supports transparency, 
though I have no idea how this fact could be exploited in Scilab.


I have quie a lot of home work to do! Thank you again for your help.

JP Grivet



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[Scilab-users] density in a graph

[Jean-Philippe Grivet]

Dear all,

I am drawing a graph in a gray scale (say from 1 to 32), using lines of 
different density. I would like that, in the region of intersection of 
two lines, the shade of gray be the sum of the densities of each line. 
How can I manage that ?


Thanks in advance for any hint

JP Grivet


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