https://developer.apple.com/library/prerelease/content/documentation/GraphicsImaging/Reference/CoreImageFilterReference/index.html#//apple_ref/doc/filter/ci/CIQRCodeGenerator
Generates a Quick Response code (two-dimensional barcode) from input data.
CIQRCodeGenerator
inputMessage |
The data to be encoded as a QR code. An |
inputCorrectionLevel |
A single letter specifying the error correction format. An Default value: |
Generates an output image representing the input data according to the ISO/IEC 18004:2006 standard. The width and height of each module (square dot) of the code in the output image is one point. To create a QR code from a string or URL, convert it to an NSData object using the NSISOLatin1StringEncoding string encoding.
The inputCorrectionLevel parameter controls the amount of additional data encoded in the output image to provide error correction. Higher levels of error correction result in larger output images but allow larger areas of the code to be damaged or obscured without. There are four possible correction modes (with corresponding error resilience levels):
L: 7%
M: 15%
Q: 25%
H: 30%
CIQRCodeGenerator Core Image Filter Reference
原文：http://www.cnblogs.com/feng9exe/p/5994929.html