根据字符串链接生成二维码

#pragma mark - InterpolatedUIImage=因为生成的二维码是一个CIImage，我们直接转换成UIImage的话大小不好控制，所以使用下面方法返回需要大小的UIImage

- (UIImage *)createNonInterpolatedUIImageFormCIImage:(CIImage *)image withSize:(CGFloat) size {

CGRect extent = CGRectIntegral(image.extent);

CGFloat scale = MIN(size/CGRectGetWidth(extent), size/CGRectGetHeight(extent));

size_t width = CGRectGetWidth(extent) * scale;

size_t height = CGRectGetHeight(extent) * scale;

CGColorSpaceRef cs = CGColorSpaceCreateDeviceGray();

CGContextRef bitmapRef = CGBitmapContextCreate(nil, width, height, 8, 0, cs, (CGBitmapInfo)kCGImageAlphaNone);

CIContext *context = [CIContext contextWithOptions:nil];

CGImageRef bitmapImage = [context createCGImage:image fromRect:extent];

CGContextSetInterpolationQuality(bitmapRef, kCGInterpolationNone);

CGContextScaleCTM(bitmapRef, scale, scale);

CGContextDrawImage(bitmapRef, extent, bitmapImage);

CGImageRef scaledImage = CGBitmapContextCreateImage(bitmapRef);

CGContextRelease(bitmapRef);

CGImageRelease(bitmapImage);

return [UIImage imageWithCGImage:scaledImage];

}

#pragma mark - QRCodeGenerator--首先是二维码的生成，使用CIFilter很简单，直接传入生成二维码的字符串即可

- (CIImage *)createQRForString:(NSString *)qrString {

NSData *stringData = [qrString dataUsingEncoding:NSUTF8StringEncoding];

CIFilter *qrFilter = [CIFilter filterWithName:@"CIQRCodeGenerator"];

[qrFilter setValue:stringData forKey:@"inputMessage"];

[qrFilter setValue:@"M" forKey:@"inputCorrectionLevel"];

return qrFilter.outputImage;

}

UIImage *boundImg = [self createNonInterpolatedUIImageFormCIImage:[self createQRForString:@"http://baidu.com"] withSize:250.0f];