根據字元串鏈接生成二維碼

#pragma mark - InterpolatedUIImage=因為生成的二維碼是一個CIImage，我們直接轉換成UIImage的話大小不好控制，所以使用下麵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));

    // create a bitmap image that we'll draw into a bitmap context at the desired size;

    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);

    // Create an image with the contents of our bitmap

    CGImageRef scaledImage = CGBitmapContextCreateImage(bitmapRef);

    // Cleanup

    CGContextRelease(bitmapRef);

    CGImageRelease(bitmapImage);

    return [UIImage imageWithCGImage:scaledImage];

}

#pragma mark - QRCodeGenerator--首先是二維碼的生成，使用CIFilter很簡單，直接傳入生成二維碼的字元串即可

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

    // Need to convert the string to a UTF-8 encoded NSData object

    NSData *stringData = [qrString dataUsingEncoding:NSUTF8StringEncoding];

    // Create the filter

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

    // Set the message content and error-correction level

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

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

    // Send the image back

    return qrFilter.outputImage;

}

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調用：

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