How do you measure length of picture using mobile phone?

[fisika1]

I would like to know how to use the phone's camera to take a picture that loads into the app, and be able to draw straight line segments, and measure length. i have tried some examples but failed to measure the length from a picture that loads into my phone

[Ramon]

Maybe this can help you:

Use camera (photo) to measure distances ( and area)

Hi I have an idea and I don't know how to do it with App inventor I want to measure distances by taking pictures with camera, in example, I will take photos like in this uploaded image, the distance of the blue ligne is known, and I ask the app for detecting and measuring the red ones. Can I do it? [antibiogramme]

[fisika1]

hai thank for your help. but i have tried this app, i can't take a picture and measure the length. how to take a picture and measure the length of the picture? thanks