Length & Width measurement of an image in Millimeters

I am able to get the length and width of an image in pixels only.I am in need of measuring the length & width in millimeters for pixels/mm for a text extraction algorithm. how to get the values in millimeter?

Answer 1

[Matt J]

You could measure, physically, the dimensions of a letter of text and then measure the same letter's dimensions in pixels in your image. Then you could deduce the size of your pixels in mm.

[Caroline David]

Is there a code for length measurements??

[Matt J]

No, there is no code for length measurements.

Answer 2

[Vijay]

Thats what i am not aware of how to measure the length & width in physical quantities.. all i get is in pixels only

[Image Analyst]

This should have been a comment, not an Answer. But anyway, you take a micrometer or ruler and lay it down on the thing you imaged - your piece of paper - and read off the length from the micrometer or ruler.

[Vijay]

I asked for help in matlab coding.. any functions that can measure physical length & breadth of the images for calculation of pixels/mm value.. i got a 1536x2048 image taken from a 3.1 megapixel camera i am in need to get the 1536x2048 in terms of millimeters for that calculation is there any method? or functions??

[Vijay]

Thanks image analyst i got your demonstration on spatial calibration. ill make sure to answer people who are asking the same question again and again thanks a lot..

[Image Analyst]

Where did you get my demo on spatial calibration?

Answer 3

[Vijay]

This link

http://www.mathworks.in/matlabcentral/answers/56087-how-can-i-find-the-spatial-calibration-factor

[Image Analyst]

Thanks - I'd forgotten about that one. It's quite a nice demo.