MATLAB: Edge direction

directionedge

Is there a function to check if an edge changes direction?

I have used bwlabel to work on connected edges, but now I only want to work on the ones that do not follow around corners. More clearly, they can be vertical, horizontal, or diagonal, but they cannot be a mixture of 2 or more…

Best Answer

Hi,

to extract edges of any direction, you just need to choose the right structuring element for a morphological opening. E.g. to extract vertical edges:

BWv = imopen(BW,[1 1 1]');

horizontal:

BWh = imopen(BW,[1 1 1]);

top left to lower right

BWd = imopen(BW,[1 0 0; 0 1 0; 0 0 1]);

and so on.

Hope this helps, W.

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MATLAB: Calculating mean angles of edge detection

Try regionprops with orientation property

Example

BWd1 = 1.0*BWd;
data = regionprops(BWd,'orientation','pixelidxlist');   % get orientation and pixels list of each region
for i = 1:numel(data)
    idx = data(i).PixelIdxList;                         % pixel indices of current region
    ori = data(i).Orientation;                          % orintation of region
    BWd1(idx) = ori;                                    % assign angle value
end
imagesc(BWd1)
colorbar

MATLAB: How can i select labeled images that are touching a specific axis,like x-axis,y-axis,and their paralel axis,also the one touches 2 axis at the same time,forexample touches x-axis and its paralel axis at the same time

To get rid of objects touching just one border is simple. Simply store the 3 edges of the image that you want to keep. Then zero out those 3 edges and call imclearborder(). Then restore the 3 edges that you zeroed out. Let's say you wanted to delete blobs touching the bottom edge only. Then

% Save 3 edges.
topEdge = binaryImage(1, :);
leftEdge = binaryImage(:, 1);
rightEdge = binaryImage(:, end);
% Zero 3 edges.
binaryImage(1, :) = false;
binaryImage(:, 1) = false;
binaryImage(:, end) = false;
% Get rid of blob(s) touching bottom edge
binaryImage = imclearborder(binaryImage);
% Restore the 3 edges.
binaryImage(1, :) = topEdge;
binaryImage(:, 1) = leftEdge ;
binaryImage(:, end) = rightEdge ;

You could build all that into a function where you pass in the edge(s) you want to remove from.

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Related Solutions

MATLAB: Calculating mean angles of edge detection

MATLAB: How can i select labeled images that are touching a specific axis,like x-axis,y-axis,and their paralel axis,also the one touches 2 axis at the same time,forexample touches x-axis and its paralel axis at the same time

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