How do you measure length of picture using mobile 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]