// 1.創建過濾器  CIFilter *filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];  // 2.恢復默認  [filter setDefaults];  // 3.給過濾器添加數據(正則表達式/賬號和密碼)  NSString *dataString = @"http://www.520it.com";  NSData *data = [dataString dataUsingEncoding:NSUTF8StringEncoding];  [filter setValue:data forKeyPath:@"inputMessage"];  // 4.獲取輸出的二維碼  CIImage *outputImage = [filter outputImage];  //因為生成的二維碼模糊，所以通過createNonInterpolatedUIImageFormCIImage:outputImage來獲得高清的二維碼圖片  // 5.顯示二維碼  self.imageView.image = [self createNonInterpolatedUIImageFormCIImage:outputImage withSize:300]; /** * 根據CIImage生成指定大小的UIImage * * @param image CIImage * @param size 圖片寬度 */- (UIImage *)createNonInterpolatedUIImageFormCIImage:(CIImage *)image withSize:(CGFloat) size{  CGRect extent = CGRectIntegral(image.extent);  CGFloat scale = MIN(size/CGRectGetWidth(extent), size/CGRectGetHeight(extent));  // 1.創建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到圖片  CGImageRef scaledImage = CGBitmapContextCreateImage(bitmapRef);  CGContextRelease(bitmapRef);  CGImageRelease(bitmapImage);  return [UIImage imageWithCGImage:scaledImage];}  

// 1.創建捕捉會話  AVCaptureSession *session = [[AVCaptureSession alloc] init];  self.session = session;  // 2.添加輸入設備(數據從攝像頭輸入)  AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];  AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error:nil];  [session addInput:input];  // 3.添加輸出數據(示例對象-->類對象-->元類對象-->根元類對象)  AVCaptureMetadataOutput *output = [[AVCaptureMetadataOutput alloc] init];  [output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];  [session addOutput:output];  // 3.1.設置輸入元數據的類型(類型是二維碼數據)  [output setMetadataObjectTypes:@[AVMetadataObjectTypeQRCode]];  // 4.添加掃描圖層  AVCaptureVideoPreviewLayer *layer = [AVCaptureVideoPreviewLayer layerWithSession:session];  layer.frame = self.view.bounds;  [self.view.layer addSublayer:layer];  self.layer = layer;  // 5.開始掃描  [session startRunning];  

// 當掃描到數據時就會執行該方法- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection{  if (metadataObjects.count > 0) {    //獲得掃描數據，最后一個時最新掃描的數據    AVMetadataMachineReadableCodeObject *object = [metadataObjects lastObject];    NSLog(@"%@", object.stringValue);    // 停止掃描    [self.session stopRunning];    // 將預覽圖層移除    [self.layer removeFromSuperlayer];  } else {    NSLog(@"沒有掃描到數據");  }}