Find a height of object using OpenCV

Question

I have an image. I have to find the height of a particular object in it.

If we directly take the pixel length it will not give the exact height.How to approach this problem?

Do you have any information about the object you are looking for? Your calibration can map a point in the image to a ray in world coordinates but that alone will not tell you the height. Without depth information about the object or several frames from different perspectives you can't resolve the height of the object. — Hammer, Aug 27 '12 at 15:16

score 4 · Accepted Answer · answered Aug 27 '12 at 08:34

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After you calibrated your camera, you will have a transformation from image plane to world coordinates. Using this information you can predict the height of the object you are looking for, of course in this step you somehow need to identify the object that you are interested in.

Generally speaking, this question is too broad and covers many fundamental concepts of computer vision, so please consult your favorite textbook before attacking the problem.

answered Aug 27 '12 at 08:34

Seçkin Savaşçı

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I have already tried camera calibration , but its not giving acceptable results, have tried homographs too. No luck. – Aizen Aug 27 '12 at 08:39
camera calibration is a common way to attack your problem, are you sure that you set up everything correctly while calibrating your camera? – Seçkin Savaşçı Aug 27 '12 at 08:40
As far as I know I have set up everything perfectly. – Aizen Aug 27 '12 at 11:31

score 1 · Answer 2 · edited May 23 '17 at 12:15

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An alternative approach: place the object on top of a A4 paper sheet and take a picture from above. Since you know the size of paper, you can calculate the size of the object based on that.

To detect a paper sheet, check this post or this.

edited May 23 '17 at 12:15

Community

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answered Aug 27 '12 at 20:12

karlphillip

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Find a height of object using OpenCV

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