calculate the area of an object in binary image

I have to calculate the area of an object in binary image. I want convert pixel to cm2 but i do not know how i do. please help me.

[roya a]

Somebody help me

Answer 1

[Image Analyst]

See my tutorial on image segmentation: http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862

See my attached demo on spatial calibration (below in blue text).

[roya a]

thank you

[roya a]

hi thank you. i have a question. what is the meaning "Enter distance in those units" in your code? thank you

[Image Analyst]

If you had a photo of the moon and asked the user what units they wanted to use, and they said km. Then they drew across the diameter of the moon, then they should enter the diameter in km. Not in inches, not in meters, not in miles, but in the units they want to use: km. So they should enter 3476 because that's the diameter of the moon in km.

[roya a]

thank you but if we had not diameter in that unit. what are we do? i have an image and we want to know when I segment that and extracted an object ,what is the object's area in real world. i don't know that diameter. i have object's area in pixel.i will want calculate object's area in real world. (pixel convert to square centimeters) thanks for your attention

[Image Analyst]

If you don't have any calibration standards then you can't. If you're looking at a picture of the moon, how can you know just from the image that it's the real moon through a telescope with a diameter of 3476 km, or a picture taken with your iPhone of a poster in your room with a diameter of 30 cm? You don't. You have to tell it.