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Hi, Yanbe. question for 0.8 version (2007-09-03 08:08 by 匿名 #31970)

I have read your 0.7.2 verison of qr code decoder. I wanna ask what kind of changes occurred in the 0.8 version.
and for this project, especially for the decoder, what algorithms did you use. would you please list the reference? I am also doing research on improve ment of 2d barcode recognize for my dissertation . I need your help.

Thank you very much

Regard Toby

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RE: Hi, Yanbe. question for 0.8 version (2007-09-03 14:11 by yanbe #31980)

Hi

About changes of version 0.8, please read this document.
http://sourceforge.jp/projects/qrcode/document/qrcode_0.8_-_Changes/

And I'm using following reference.

QR Code specification
JIS-X-0510(2004) (Japanese)
http://sourceforge.jp/projects/qrcode/document/qrcode_specification_ja/en/1/qrcode_specification_ja.pdf

Basically, I obey the method of JIS-X-0510 how to recognize QR Code symbol from its image. But some un-documented method like QRCodeImageReader#applyCrossMaskingMedianFilter are used for improving decoding performance.

Some tables like QRCodeSymbol#numRSBlocks and QRCodeSymbol#numErrorCorrectionCode are ported from this specification. It is essential for process after decoder recognized symbol.

ISO/IEC18004
(English version of above)
It will be useful for most developers. But it costs over $100. Perhaps it is available on library.

ReedSolomon error correction code
I ported C version of ReedSolomon code below into Java.
http://sourceforge.net/projects/rscode

Yusuke Yanbe
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RE: Hi, Yanbe. question for 0.8 version (2007-09-04 00:52 by drhu00 #31994)

Yanbe,
A Question: Why other twp eccPerRSBlock not divided by 2 in correctDataBlocks? There is some reason for it?
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RE^2: Hi, Yanbe. question for 0.8 version (2007-09-04 02:41 by yanbe #31999)

drhu,

Because (as in comment) QR Code specification JIS-X-0510(2004), p30 says,

"in order to protect from miss-error correction, number of error correction shold be less than half of error correction code".

And I confirmed that this modification improve decoding rate slightly with my local test correction.
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RE: RE^2: Hi, Yanbe. question for 0.8 version (2007-09-04 02:54 by drhu00 #32000)

I know why you divided by 2. But what I don't know why you don't divided by 2 for other similar ones in //symbol has 2 types of RS blocks
Should we treat the same? I mean also divide by 2 in ReedSolomon corrector = new ReedSolomon(shorterRSBlocks[i], eccPerRSBlock);
and
ReedSolomon corrector = new ReedSolomon(longerRSBlocks[i - numShorterRSBlocks], eccPerRSBlock);
?
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RE: RE^2: Hi, Yanbe. question for 0.8 version (2007-09-04 03:24 by yanbe #32002)

> ReedSolomon corrector = new ReedSolomon(shorterRSBlocks[i], eccPerRSBlock);
and
> ReedSolomon corrector = new ReedSolomon(longerRSBlocks[i - numShorterRSBlocks], eccPerRSBlock);
?

Ah, you are right. We have to treat them same.
These part also should be divided by 2

Then I will update release files soon.

Thank you.
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