Update: QR Decoding and External Libraries

QR codes are an important feature to the project. I have implemented image loading and QR decoding. Part of the implementation involved familiarizing myself with Qt's build process in order to make use of 3rd party libraries. Qt's image selector is specialized on iOS so that users can select a picture from the native gallery. I used the Quicknative library to provide similar functionality on Android. It uses Qt's Java interface to create Java objects and make calls to the Android API in order to provide users access to a native Android gallery for their image selection. I also used the quirc QR decoding library, which searches a given image for QR patterns using a standard floodfill-based algorithm, then it uses the corners of the QR code to straighten the image with a perspective transform. I had to fork this library in order to add C++11 support and a qmake build file `quirc.pri` so that any Qt project can make use of quirc.  After importing these third party libraries, I parsed the `file:///` path, loaded it as QImage, performed some image processing, converted the image to a character array in order to  run quirc's detection and decoding algorithm. Quirc can process pictures which unambiguous represent a QR code and are  distorted only by a perspective transformation (for example, if the picture was taken from the corner of a room). In case of decoding failure, we are able to send the image to the server.  The next step is to perform QR decoding a separate thread, display a loading bar, and let users crop images before processing.


-- Hugo