Angle of lines in binary image
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I would like to kindly ask you about computing angles in binary image. I have this binary image (and many similar), containing three binary objects. I need to fit such binary (white) objects with lines, and mainly compute angles of this lines to each object would be represented by one angle.
I tried to do that by I was not successful. I just know that MATLAB contains the inbuilt function polyfit(), which should be the way to approximate such binary objects but I cannot implement that. I would need to store these angles in some variable. For instance, when I have such binary image with three binary objects, this variable such contain three angles.
Thank you very much for the help.
Matt J on 6 Jun 2021
Edited: Matt J on 6 Jun 2021
It may be helpful to use linear2dFit from this FIle Exchange package
Angles=-[lfit.angle], %line angles in degrees
38.2326 43.5104 55.4355
Image Analyst on 6 Jun 2021
Try polyfit like this:
% Read in image (the posted image is RGB).
binaryImage = imread('image.png');
% Convert from color image to logical
if size(binaryImage, 3) > 1
binaryImage = binaryImage(:,:,1) > 0;
imshow(binaryImage); % Display image.
axis('on', 'image'); % Display axis tick marks
% Identify separate connected components. (Could also use bwlabel)
props = regionprops(binaryImage, 'PixelList');
for k = 1 : length(props) % For each blob...
% Get coordinates of the points in the blob.
x = props(k).PixelList(:, 1);
y = props(k).PixelList(:, 2);
% Fit a line
coefficients = polyfit(x, y, 1);
% Get endpoints of the line
x1 = min(x);
y1 = polyval(coefficients, x1);
x2 = max(x);
y2 = polyval(coefficients, x2);
% Draw line from left most x to rightmost x.
line([x1,x2], [y1,y2], 'Color', 'r', 'LineWidth', 3);
% Compute angle with origin at (1,1) which is the upper left corner of the image, as usual.
angle(k) = atan2d(y2-y1, x2-x1);
% In case you wanted it from the other corner, the lower left corner.
angle2(k) = atan2d(y1-y2, x2-x1);
% Report angles to command window.