# Image processing and contour detection

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KATHAN BHAVSAR il 12 Apr 2023
Risposto: Image Analyst il 15 Apr 2023
With respect to the image below, how can I detect the the upper (red) and lower (green) contour on the boundaries shown n the image below. Also, how do I calculate the distance between the two boundaries (blue)?
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### Risposta accettata

Sachin il 14 Apr 2023
Hi
I understand that you want to find the contours in the image.
I suggest you to use Image processing and Computer Vision Toolbox. The toolbox provides two functions -
1. ‘bwboundaries' – This function is used to compute the boundary of a binary image . It takes a binary image as input and computes the boundary of the connected region in the binary image
2. ‘bwtraceboundary’ – This function is used to trace a boundary in a binary image.It takes a binary image as input and a starting point on the boundary and trace the boundary of the connected region in the image.
These function provides boundary coordinates that can be used find the distance between two points
grayImage = rgb2gray(image);
threshold = 50; % Set threshold value
binaryImage = grayImage > threshold;
boundaries = bwboundaries(binaryImage);
imshow(image);
hold on;
for k = 1:length(boundaries)
boundary = boundaries{k};
plot(boundary(:,2), boundary(:,1), 'b', 'LineWidth', 2);
end
If you encounter any issues with these functions, you can also use OpenCV library to find contours.
Please refer the following page for more information about boundary function:
Please refer OpenCV documentation for more information on finding contours
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KATHAN BHAVSAR il 15 Apr 2023
Thank you, I will certainly try this out.

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### Più risposte (1)

Image Analyst il 15 Apr 2023
To find average width of a blob, see attached demo.
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