How to match voronoi area to it's point

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Amit Ifrach
Amit Ifrach 2021-8-18
评论： Bjorn Gustavsson 2021-8-18
לק"י
Hi!
I'm trying to find a command or a code that can match the voronoi areas I get out from voronoin command to the points they enclose. I use oast of KSSV's code, so if it seems fermiliar, it's from him.
thanks!
that's the code:
[v,c] = voronoin([xroi yroi]) ;
vorareaacd45num10thin1st = zeros(length(c),1) ;
for i = 1:length(c)
v1 = v(c{i},1) ;
v2 = v(c{i},2) ;
vorarea(i) = polyarea(v1,v2) ;
end
  2 个评论
Amit Ifrach
Amit Ifrach 2021-8-18
לק"י
Hi Image Analyst, thanks for the answer!
I'll explain the main goal and then maybe i'll be able to explain what I need a little bit better.
I'm imaging a cell down to it's single molecule level. I want to use voronoi diagram on the cell's 'image' (it's xy csv of the points of the molecules). the problem is that the image contains alot of background noise that I need to ignore and to take only the voronois areas in the cell.
The (wrong) startegy I wanted to use was to inpolygon on points within the cell, delete everything else outside of it and afther that to do a voronoi. the problem is that allways I'll get big areas at the edge of the cell and cutting out points won't help. I want to use inpolygon to 'take out' the areas within the drawn polygon instead.
The problem is, that my code generate voronoi areas without a way to recognize which areas they are, or which point the surround. I need a way to ascribe area to dot it surrounds so I can 'take out' these points using inpolygon.
is there any way to do so? I thought to do it manually with for loop, but I don't know how the voronoin command assigns the areas to the c vector (which x and y point does it use).
thanks!
Amit.
Bjorn Gustavsson
Bjorn Gustavsson 2021-8-18
The way I recall the Voronoi-boundaries are built from the line-segments prependicular to the midpoints of the Delaunay-triangulation-edges (normals halfway on the nearest-neighbour-lines, so the dual of the Delaunay-triangulation). If you could share a typical image it might be easier to modify your aproach?

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回答（1 个）

Bjorn Gustavsson
Bjorn Gustavsson 2021-8-18
The way I interpret your question each point [xroi,yroi] will be inside one Voronoi-cell (though my QD-tests leave a couple of edge-points outside the Voronoi-cells?). It should be possible to find out which by using inpolygon:
for i1 = length(c):-1:1
v1 = v(c{i1},1);
v2 = v(c{i1},2);
idx = find(inpolygon(xroi,yroi,v1,v2));
if ~isempty(idx)
idxXYinCellj(i1) = idx(1);
end
if numel(idx) > 1
disp(['Cell ',num2str(i1),' contains ',num2str(numel(idx)),' points?'])
end
end
HTH

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