How can we get the index of points that are inside a polygon?

Question

soloist 2019-2-19

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/445754-how-can-we-get-the-index-of-points-that-are-inside-a-polygon

回答： KSSV 2019-2-19

I have an image and I rotate it with imtransform function.The Output of this function is an image that has black sections in the four corners of the image. I want to extract frame and descriptor of that except black parts in the corner of the image by vl_dsift.for do this I use the below code:

th = 50;
s = 0.8;
A = imread('cameraman.tif');
[H,W]= size(A);
T = [s*cosd(th), -s*sind(th), 0 ; s*sind(th), s*cosd(th) ,0; 0, 0 ,1];
B  =imtransform(A,maketform('projective',T'),'xdata',[-W/2 W/2],'ydata',[-H/2 
H/2],'udata',[-W/2 W/2],'vdata',[-H/2 H/2]);
P = [-W/2 ,W/2 W/2 ,-W/2; -H/2 ,-H/2 ,H/2, H/2; 1, 1, 1 ,1];
Pt = T*P;
Pt = Pt./repmat(Pt(3,:),3,1);
Pt = Pt(1:2,:);
opts = {'size', 8, 'step', 5, 'fast'}; 
[fb, db] = vl_dsift(single(B), opts{:});
in = inpolygon(fb(1,:),fb(2,:),Pt(1,:),Pt(2,:));