#102 Rotation stops QR recognition

[Matthias Philipp]

QR code is not recognized if image is upside down. The two images are the same, except the lossless 180 degree rotation which was done with jpegtran.

zbarimg.exe --verbose=32 demo-180-fail.jpg
_zbar_process_image: processing: Y800(30303859) 1651x231 @010FC718
_zbar_qr_decode: 53x46 finders, 3 centers:
scanned 0 barcode symbols from 1 images

WARNING: barcode data was not detected in some image(s)
  things to check:

    - is the barcode type supported?  currently supported symbologies are:
      EAN/UPC (EAN-13, EAN-8, UPC-A, UPC-E, ISBN-10, ISBN-13),
      Code 128, Code 39 and Interleaved 2 of 5
    - is the barcode large enough in the image?
    - is the barcode mostly in focus?
    - is there sufficient contrast/illumination?

dump_stats: symbol sets allocated   = 1
dump_stats:     scanner syms in use = 0         recycled  = 0
dump_stats:     image syms in use   = 0         recycled  = 0
dump_stats: symbols allocated       = 0
dump_stats:      recycled[0]        = 0
dump_stats:      recycled[1]        = 0
dump_stats:      recycled[2]        = 0
dump_stats:      recycled[3]        = 0
dump_stats:      recycled[4]        = 0
_zbar_qr_destroy: max finder lines = 63x63

Now, same image rotated by 180°:

zbarimg.exe --verbose=32 demo-ok.jpg
_zbar_process_image: processing: Y800(30303859) 1651x231 @02BF0848
_zbar_qr_decode: 53x46 finders, 3 centers:
**_zbar_process_image: QR-Code: IR,5122,05,2026 (4 pts) (q=1) (new)**
QR-Code:IR,5122,05,2026
scanned 1 barcode symbols from 1 images
dump_stats: symbol sets allocated   = 1
dump_stats:     scanner syms in use = 0         recycled  = 0
dump_stats:     image syms in use   = 0         recycled  = 0
dump_stats: symbols allocated       = 1
dump_stats:      recycled[0]        = 0
dump_stats:      recycled[1]        = 0
dump_stats:      recycled[2]        = 0
dump_stats:      recycled[3]        = 0
dump_stats:      recycled[4]        = 0
_zbar_qr_destroy: max finder lines = 63x63

The image is part of a scanned page which was cropped during debug.