CODEWITHSUNDEEP
imagepixelmeasurementphotographyunit-conversion
ali samah
ali samah

Reputation: 1

Convert object length from pixels to cm without knowing the calibration factor

In a digital image, size (or distance) is measured in pixels.

Is there any method to find the actual size of an object in an image without knowing the calibration factor?

Upvotes: 0

Views: 382

Answers (1)

Dev-iL
Dev-iL

Reputation: 24169

To my knowledge, there is no general solution to this.

  • For specific objects (mostly those that are mass produced, or have specs/drawings available) you might be able to find the "calibration factor" after the fact. Alternatively, if there's anything else in the photo that has known dimensions, you might be able to use that to compute the size of the object you care about (for example - consider images that come from fancy microscopes, that have a "scale" indicator somewhere on the image).
  • If you have the details of the photodetector (e.g. pixel size; assuming it's an electronic device), the parameters of the lens being used when taking the photo, the distance to the object etc., you might be able to estimate the object size using straightforward optical computations (like Geometrical optics).

Upvotes: 5

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