Datamatrix/QRCode online resource for encoding?

Is there any free online 开发者_StackOverflow中文版resource explaining how to encode those barcodes?

This page should explain the encoding algorithm:

https://web.archive.org/web/20100830111303/https://www.swetake.com/qr/qr1_en.html

The ZXing project has an encoder for QR codes. It's not really an explanation of the QR code spec, since ISO 18004 is for-pay, but might be better than nothing, depending on your purpose.

From the Wikipedia entry:

Although this is a free standard, there are no free documents that explain the encoding process. Documentation in PDF or paper format can be purchased from the ISO web site.