# Determine size a person using ImageJ

Given an photograph of a person I want to determine how tall the person is.

I have the following information:

• picture 12M pixel

• the camera’s parameters from the images EXIF (focal length: native and 35mm equivalent, resolution, aperture and shutter-speed)

• the dimensions of an object held by the person (at the center of the torso).

Which is the best and most accurate method to determine how tall the person is ?

Hi,
You can draw a line ROI on the reference object and measure it. You can then draw a line on the person, measure it and perform a cross multiplication to get the size.
With the measurement of the reference object, you can also calibrate your image (Image> Properties) so that the measurement of the line ROI of the person will give you directly the calibrated measurement.

Nico

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Hi

thank you. I tried it. But measuring the reference object and the person. I divide the person measurement by the reference object length. I end up with the person being only 1.3 meters tall. I use the real world length of the reference object multiplied by how many times it fit into my person"s length in the image.

I must be doing something wrong. The reference object is not perfectly horizontal. And there is an angle in the image. Its probably the angle…

Any ideas ?

Thanks!

Hi,
Could you post an example image ?

Nico

I really think you have to calibrate your system.
Something like this:

https://it.mathworks.com/help/vision/single-and-stereo-camera-calibration.html?s_tid=CRUX_lftnav

I’ve never done and I also think python, java, opencv and other open source environment have functions and toolboxes to deal with this.
These links are just to have some starting point.