# How can I convert pixel coordinate to micrometer in x and y axis in an image?

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engineer on 1 Jun 2018
Commented: Florian Morsch on 2 Jun 2018
Hi everyone I have an image and in the binary image, a single point coordinate is detected as x and y-axis in pixels. However, I actually wanna know the coordinates in micrometer. Would it be possible to get this info from the image? I am thinking that I have to measure something that I know the length of it and then convert it from pixel to micrometer?
Thanks

Florian Morsch on 1 Jun 2018
Your idea is correct. Take a reference object from which you know the exact measurements and convert that to the pixel lenght. Note that the picture of the reference object and the object you want to measure should be both taken with a fixed camera under same conditions if possible.
Lets say you have a cube with 10mm side lenght, which is 100 pixel in the image. So now you know that 1 pixel equals 0.1mm. If you now take another image with the camera in the same place, a object with 200 pixel lengh equals 20mm. If you move your camera and/or change some other conditions you might have to measure the reference again.
What you also can do is calibrate your camera with a known pattern (checkerboard for example) and then measure a object. This article might help you with that: https://de.mathworks.com/help/vision/examples/measuring-planar-objects-with-a-calibrated-camera.html

engineer on 1 Jun 2018
Thanks for your reply. Is there any auto calibration method for image processing?
Florian Morsch on 2 Jun 2018
There is the Camera Calibration App in Matlab, its basically the first part in the link i send in my first answer.