Coordinates of corners of quadrilateral in binary mask

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João Miguel Ribeiro 2019-10-21

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评论： Matt J 2020-10-28

I'm doing a project on computer vision in which I have to compute some homographies and perform image stitching. I also have to provide the coordinates of the corners of each image in the final panorama.

Essentially, what I need is to determine the [x,y] coordinates (or i,j indices) of the four corners of a quadrilateral in a binary mask (example in the image below).

I coded a pretty computationally inefficient function to do it. But it misses one of the corners whenever the quadrilateral is a trapezoid (which is most of the time). I tried fixing it but haven't managed to get it quite right. I have tried to detect edges and lines using the hough algorithm and then getting the intersections of those lines but the results aren't precise and looks like a complicated way of solving a somewhat simple problem. Any matlab functions or implementation ideas for this task?

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darova 2019-10-22

Rotate image and find min/max (x,y)

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采纳的回答

Matt J 2019-10-22

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编辑：Matt J 2019-10-22

在 MATLAB Online 中打开

The Computer Vision Toolbox has some ready-made corner detection functions, e.g.,

https://www.mathworks.com/help/vision/ref/detectmineigenfeatures.html

https://www.mathworks.com/help/vision/ref/detectharrisfeatures.html

You could also try this improvised algorithm:

N=360;
theta=linspace(0,360,N);
[I,J]=find(Image);
IJ=[I,J];
c=nan(size(theta));
for i=1:N
   
    [~,c(i)]=max(IJ*[cosd(theta(i));sind(theta(i))]);
    
    
end
H=histcounts(c,1:numel(I)+1);
[~,k] = maxk(H,4);
corners=IJ(k,:)