How do I isolate lines at a certain angle in an image.

Good day, I am trying to isolate the lines at an angle of 45 degrees in an image. The isolated lines should be the only lines present or occurring in the output file. Below is a link of a sample .jpg file

Answer 1

[Akira Agata]

Same as previous post, you can utilize regionprops function, like:

% Read your image and binarize
I = imread('5159-15B front_imgJ-macro.jpg');
I = rgb2gray(I);
BW = imbinarize(I);

% Apply regionprops function
s = regionprops(~BW,{'MajorAxisLength','MinorAxisLength','Orientation','PixelIdxList'});
s = struct2table(s);

% Extract the regions which satisfies both the following conditions:
% (1) (Minor axis length)/(Major axis length) <= 20%
% (2) Angle with horizontal line is +/-45 degree with 10 degree margine
idx =...
(s.MinorAxisLength ./ s.MajorAxisLength <= 0.2) &...
(abs(abs(s.Orientation)-45) <= 10);
s = s(idx,:);

% Show the result
BWout = true(size(BW));
for kk = 1:height(s)
  BWout(s.PixelIdxList{kk}) = false;
end

figure
imshow(BWout)

[N/A]

How about if i want to show a range of angles, let's say angles within the range of 10 and 80

[Akira Agata]

If you want to extract lines with an angle of 10~80 and -80~-10 degree, please change the condition of idx in the script as follows:

idx =...
(s.MinorAxisLength ./ s.MajorAxisLength <= 0.2) &...
(((10 <= s.Orientation) & (s.Orientation <= 80)) |...
((-80 <= s.Orientation) & (s.Orientation <= -10)));