Count real size of object in photo

asked 2018-05-13 08:06:39 -0500

Raiper34 gravatar image

updated 2018-05-13 08:08:47 -0500


I am working on my project, but I have problem. I have photo of wound with some pen or similar marker and I know width of this pen, real width of pen in cm and width of pen on this picture in pixels. Then I have wound and I know number of pixels in wound area, and Now I need to compute real size of wound area in centimeters. Itired lot of things, but always number is far away from excepted number, I know, it will be newer exactly as in real, but number is sometimes 2x bigger. I think this formula should work: penLengthCM * woundAreaPX / penLengthPX. But it does not work, I even tried some variqations with sqrt, but no success. Can anybody help me?

You can see example of this on image below: image description

edit retag flag offensive close merge delete


Get a camera with a depth sensor. From there it’s just a matter of geo trig.

sjhalayka gravatar imagesjhalayka ( 2018-05-13 10:40:10 -0500 )edit

Your formula is never going to work, depth information is lost when 3D real world points get mapped to the 2D image plane, thus the measure using the pixel/mm ratio can be taken ONLY for objects standing at the same distance (which is not the case). As said you need a depth sensor to achive the result.

David_86 gravatar imageDavid_86 ( 2018-05-14 02:07:22 -0500 )edit