Find the actual distances in an image.

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Chathu on 15 Apr 2016
Commented: Chathu on 30 Apr 2016
I want to find the minimum x(1) value which touches the image,A. Then maximum x(2) value which touches the image,A.(ps:image is attached). I made the axis ON. SO i want to let the program identify the x(min), x(max),y(min) and y(max), next draw straight lines(as shown in the image) along above said points(eg:x(1),x(2),etc) and then perform the spatial calibration (note; image is not symmetric). Can anyone give me a hint how to resolve this issue.
Chathu on 15 Apr 2016
it is an image. Let me add it here now. Sorry for the confusion.

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Accepted Answer

Mohammad Abouali
Mohammad Abouali on 15 Apr 2016
Similar approach to this should work:
I=padarray(I,[1 1 0],0);
thresh = 15;
mask = ~(I(:,:,1) < thresh & I(:,:,2) < thresh & I(:,:,1) < thresh);
xProj = any(mask);
xMin = find(xProj,1,'first')-0.5;
xMax = find(xProj,1,'last');
yProj = any(mask,2);
yMin = find(yProj,1,'first');
yMax = find(yProj,1,'last');
hold on
plot([xMin xMin],ylim,'r','LineWidth',2)
plot([xMax xMax],ylim,'r','LineWidth',2)
plot(xlim,[yMin yMin],'r','LineWidth',2)
plot(xlim,[yMax yMax],'r','LineWidth',2)
Chathu on 30 Apr 2016
@ Mohammad, i saw your response just now. Your approach is perfect for my purpose, as it is short distance.
Thank you so much for your response. Highly appreciate it:)

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More Answers (1)

Image Analyst
Image Analyst on 16 Apr 2016
See my spatial calibration demo.
  1 Comment
Chathu on 16 Apr 2016
Thank you so much Image Analyst. Highly appreciated.

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