MATLAB: Convert binary ROI to polygon

image processingregion of interest

I have a binary image with a concave polygon drawn in a paint application. Using find() I get a set of points, but they aren't ordered so all the MATLAB polygon functions choke on them. How do I go about turning my 2D line-mask into a proper polygon variable?

Edit: added example

Edit2: It was drawn with 1px pencil in a continuous motion, then 'cleaned' with bwareaopen(). So each pixel should have at most 2 neighbours.

Best Answer

http://www.mathworks.com/help/images/boundary-tracing-in-images.html

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MATLAB: Find the centroid of any shape

Of course. Yes, that is correct. As you probably know, the centroid is only guaranteed to be inside the shape if the shape is convex. For some arbitrarily irregular shape, the centroid may be inside or outside the shape. Are you just stating a fact for others who may not know this, or do you have a question?

MATLAB: I have RGB (MxNx3) image and a binary mask (MxN). I want to place this mask over the RGB such that a line should be shown along the shape of the mask on the RGB image.

Call bwboundaries() then plot

boundaries = bwboundaries(binaryImage);
numberOfBoundaries = size(boundaries, 1);
hold on;
for k = 1 : numberOfBoundaries
  thisBoundary = boundaries{k};
  plot(thisBoundary(:,2), thisBoundary(:,1), 'r-', 'LineWidth', 2);
end
hold off;

Best Answer

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MATLAB: Find the centroid of any shape

MATLAB: I have RGB (MxNx3) image and a binary mask (MxN). I want to place this mask over the RGB such that a line should be shown along the shape of the mask on the RGB image.

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