Calculating area of a shape in an image

How to calculate the actual area (in Cm^2) for an irregular shape in an image?? Please help me.

Answer 1

[Image Analyst]

You need to know the size of your image's total field of view, or an object of known size in the image, so that you can calculate a pixels/cm calibration factor. Then calculate area in pixels as usual (bwlabel, regionprops) and multiply by the square of the calibration factor.

Answer 2

[Image Analyst]

There's an app for that: http://hight3ch.com/the-app-that-can-measures-everything-from-your-photos/#more-7597