defining a polygon area within an array
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I have a 2D array of numbers.
I have a polygon with defined x and y coordinates.
Could someone please help me set the area within the array that the polygon overlaps to 0 please.
回答（2 个）
Akira Agata
2020-3-26
How about the following solution?
% 100-by-100 sample matrix
Zin = peaks(100);
Zin = Zin - min(Zin(:));
% Example of polygon
pgon = polyshape([10 10 80 30], [10 30 30 10]);
% Create logical index which indicates inside/outsize the polygon
[colGrid,rowGrid] = meshgrid(1:size(Zin,2),1:size(Zin,1));
idx = isinterior(pgon,[colGrid(:),rowGrid(:)]);
idx = reshape(idx,size(Zin));
% Set elements inside the polygon to 0
Zout = Zin;
Zout(idx) = 0;
% Show the result
figure
subplot(2,2,1)
contourf(Zin)
title('Original','FontSize',14)
colorbar
subplot(2,2,2)
plot(pgon)
xlim([1 100])
ylim([1 100])
box on
title('Polygon','FontSize',14)
subplot(2,2,3)
contourf(Zout)
title('Result','FontSize',18)
colorbar
Walter Roberson
2020-3-26
0 个投票
If you have the Computer Vision Toolbox, then you can use https://www.mathworks.com/help/vision/ref/insertshape.html#btppvxj-1-shape insertShape with 'filledpolygon' and 'Color', 'k' . This will write 0s into the part of the rectangle indicated by the coordinates. The resulting array will have been converted to RGB, but you can just take the first pane of it.
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2020-3-26
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