How to judge a point whether inside a closed contour or not?

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John W. Z
John W. Z 2016-3-21
评论： John W. Z 2016-3-22
Assume a circle contour image matrix
c= [ 0 0 0 0 1 0 0 0 0
0 0 0 1 0 1 0 0 0
0 0 1 0 0 0 1 0 0
0 1 0 0 0 0 0 1 0
0 1 0 0 0 0 0 1 0
0 0 1 0 0 0 1 0 0
0 0 0 1 0 1 0 0 0
0 0 0 0 1 0 0 0 0 ]
and a point p=[4 3], apparently inside this circle. But, how to make such judgement in matlab.

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Walter Roberson
Walter Roberson 2016-3-21
http://www.mathworks.com/help/images/ref/imfill.html imfill ('holes'). If the point gets assigned a non-zero value then it is inside a closed contour.
  2 个评论
Image Analyst
Image Analyst 2016-3-22
Clever. If you want to know if it's on the perimeter or inside (not on perimeter) then check c first
if c(4,3)
% On perimeter.
else
filledc = imfill(c, 'holes');
if filledc(4,3)
% Inside, not on perimeter
else
% Not inside any closed contour at all
end
end
If you don't care whether it's on the perimeter or inside, just do
filledc = imfill(c, 'holes');
if filledc(4,3)
% Inside, or on perimeter
else
% Not inside any closed contour at all
end

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