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I can decode a PDF's QR-code made by PDF PRINT DRIVER
(as like PrimoPDF http://primopdf.en.softonic.com/).

However, I CANNOT decode a PDF's QR-code made by PAPER SCANNING, and get the following message as...


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

_thing 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 bacode mostly in focus?
___- is there sufficient contrast/illumination?


I don't think it is due to resolution because the QR-code is scanned by 400dpi.
Please tell me what to do.

aaaaa0a
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1 Answers1

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I don't think it is due to resolution because the QR-code is scanned by 400dpi.

It is not the resolution, it is the quality of the scanned document.

If you look at the (somewhat enlarged) working sample, you see black areas where the QR is black and white areas where it is white:

sucsessed_symbol_is_a_letter_of_a.pdf screenshot

On the other hand, if you look at the failing sample, you see a mixture of black and white spots where the QR is black:

enter image description here

Thus, it is no surprise that your barcode recognition software fails.

As I don't know the quality of the paper printouts which you scan and the options your scanner offers, it is hard to say whether the scanning process as such can be improved to provide recognizable QR codes.

It might be worth a try, though, to pre-process the scanned image, using some image processor that removes noise pixels.

mkl
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