How do I make an app that can take a picture from camera and measure the area?

anybody can help me to make this app? I want to make an app that take a picture from my moblie phone and than I can measure the area. I have tried to make it,and the image from camera can be displayed in my mobile phone screen, but i can not measure the area. thanks for your help

Several suggestions in thi discussiion Use camera (photo) to measure distances ( and area) - #7 by German_Skena

thank you Steve. but I want to measure the drape of fabric which sometimes it is in any area. could you help me to measure any y area of an object from my mobile phone? thank you for your kind and help

You would need a reference in your photo in order to be able to get some approximation of size/area:

so the pen is @ 15.3cm long by @ 1.0cm high

Once you have something like this you could overlay a grid, sized to your referenc,e to help with on screen measurements.

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Also, apparent size will be at play. So, the user will have to find the ratio between the distance of the camera from an object and the apparent size of the object, then use this ratio to calculate the actual size when the distance is known.