// 1. 创建一个二维码滤镜实例(CIFilter)
    CIFilter *filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
    // 滤镜恢复默认设置
    [filter setDefaults];

    // 2. 给滤镜添加数据
    NSString *string = @"594589850445580904903";
    NSData *data = [string dataUsingEncoding:NSUTF8StringEncoding];
    // 使用KVC的方式给filter赋值
    [filter setValue:data forKeyPath:@"inputMessage"];

    // 3. 生成二维码
    CIImage *image = [filter outputImage];

    // 4. 显示二维码
    self.imageView.image = [self createNonInterpolatedUIImageFormCIImage:image withSize:80];

#pragma mark - 将模糊图片转换成高清图

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

    CGRect extent = CGRectIntegral(image.extent);
    CGFloat scale = MIN(size/CGRectGetWidth(extent), size/CGRectGetHeight(extent));

    // 1.创建bitmap;
    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);

    // 2.保存bitmap到图片
    CGImageRef scaledImage = CGBitmapContextCreateImage(bitmapRef);
    CGContextRelease(bitmapRef);
    CGImageRelease(bitmapImage);
    return [UIImage imageWithCGImage:scaledImage];
}