OCR reading of MRZ in-app

[jonathanraes]

Read the MRZ and save the contents as String

• [x] Camera frame
• [x] Reading String
• [x] Check checksum
• [x] Passport checksum
• [x] Return result as HashMap to MainActivity
• [x] Improved passport reading using full-res camera frames
• [x] Continuous detection?
• [x] Optimize detection speed
• • [x] Create N threads where N is amount of cores on device. Then start new OCR with new frame in new thead if one is available about every 0.5 - 1 sec (about N/3 where 3 is avg detection time)
• [ ] Tests
• • [x] Mrz validation
• • [x] Tesseract OCR testing?
• • [ ] Camera and activity code?
• [ ] Remove all unneeded code - some shit like in setupcameraoutputs does tings related to orientation, which seems not needed?
• [x] mrz.traineddata seems to cause crashes sometimes/on some devices?
• [x] camera frame is upside down when rotated 270 degrees

Possible improvements to OCR

• [ ] adaptive thresholding (requires #opencv?) (mostly accuracy improvement when lighting is not uniform, maybe some performance)
• [ ] try load_freq_dawg=0 and load_system_dawg=0; theoretically prevents loading of the standard frequency dictionaries
• [ ] specify page segmentation mode as described here
• [ ] OpenCV 2.4.8 manipulation example in java here, howto add opencv lib here

TODO Before ready for develop merge:

• [x] semaphore to protect device storage access
• [x] finalize delays between thread starts and restarts, make them easily settable
• [x] Fix behaviour on device rotation and sleep
• [x] delete all commented out code + maybe some more useless code
• [x] try to remove black bar in portrait mode
• [x] handler tries to restart ocr scan thread after activity has finished
• [x] correct thread handling

lots of parameters - bad documentation

[jonathanraes]

ocr() - 1 2 camera2 api - 1 mrz info - 1 2

[wkmeijer]

iOS app for scanning MRZ of passport: https://github.com/evermeer/PassportScanner

[wkmeijer]

Changing the contrast of the bitmap has no noticeable influence on the accuracy.

[jonathanraes]

Now ready for review/merge.

Black bar is still there, caused by seting aspect ratio on autoFitTextureView. Reduced by hardcoding value of 150. See setUpCameraOutputs() line 501

[wkmeijer]

For testing see #49