In working towards an app that guide VI to navigate indoors (Blind Navigation System Using QR Code), I am working out the distance of a QR code from the navigator. This will allow the app to works like iBeacon that could tell the distance of navigator from the device.
OpenCV already have methods that could measure object dimension from a known reference. The first step is to convert the known dimension to pixel ratio. This will allow for different camera with different megapixel count. The formula is simple. ratio=pixle/real size of object.
With this constant, I will need to determine the distance from the navigator to the QR code. First I find the QR code then measure the QR Code size. The QR code most likely have to be enclosed within a rectangle so as to allow the measurement of the rectangle. Convert this size (in pixles) by the formula size=pixle*ratio. Viola, we get the distance from the QR code.
Measuring the position of the QR code is an essential metric. This will allow navigator to know the direction towards the QR code. This is easily done by getting the center point of the camera view then get the relative position of the QR code to the center point. We can inform the user whether it is to the right or left. Calculating the distance from the center point is quite meaningless as it is not useful to the navigator.
Unless navigator has a perfect memory of the position of all the QR code, there is a need for a map of the location with precise point of all the QR codes. The app should also allow the plotting of routes from one QR code to another so as to provide a voice guided navigation for the VI.
Deviating from the QR code will be an issue. Unlike iBeacon, once the QR code is not in the camera view, VI is practically lost. A facility to turn VI back to the track has to be made by approximating the last known point.
