How can I calculate area of target object with Calibrated Camera

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Maitreya Maity on 24 Feb 2016
Commented: Maitreya Maity on 24 Feb 2016
I have followed the url [http://in.mathworks.com/help/vision/examples/measuring-planar-objects-with-a-calibrated-camera.html] to get idea on Measuring Planar Objects with a Calibrated Camera. The example provides codes to measure the diameter of coins. I believe the same code will help detect any other target object (circle/square etc). However, I would like to measure the area of the target object. Please help me on measuring area of target object.

Dima Lisin on 24 Feb 2016
That would depend on the object. If it is circle, and you can measure its diameter, then you can calculate its area as pi*r^2. If it is a square, then you would need to detect its corners in the image, find their world coordinates, measure the side of the square and calculate its area.
Maitreya Maity on 24 Feb 2016
Thank you for your reply. I am new in Matlab. If you kindly provide steps in details (code), it will be really helpful for me. Moreover, if the object shape is arbitrary then how can we go for area calculation. In general, we calculate number of pixel residing in the segmented object and the number of pixel is the area. Is there any way, where we can know/map the measurements of image pixel with world.