iOS拍照定制之AVCaptureVideoDataOutput

• 问题

  领导看了前面做的拍照，问了句"哪来的声音",

  "系统的，自带的，你看系统的拍照也有声音"

  "有办法能去掉吗？挺糟心的"

  "我试试"

• 思路

  路漫漫其修远兮，吾在度娘+SDK中求索

  拍砖AVCaptureVideoDataOutput, 代理方法中将CMSampleBufferRef转成UIImage

• 上码

  • session设置不提

  • layer设置可参考上篇 [iOS拍照定制之AVCapturePhotoOutput] 以及 上上篇[iOS写在定制相机之前]

  • 获取摄像头、取到设备输入添加到session、初始化videoOutput添加入session

  AVCaptureDevice *device = [self cameraDevice];
  if (!device) {
      NSLog(@"取得后置摄像头出问题");
      return;;
  }
  
  NSError *error = nil;
  self.videoInput = [[AVCaptureDeviceInput alloc] initWithDevice:device error:nil];
  
  // 设备添加到会话中
  if ([self.captureSession canAddInput:self.videoInput]) {
      [self.captureSession addInput:self.videoInput];
  }
  
  [self.videoOutput setSampleBufferDelegate:self queue:self.videoQueue];
  if ([self.captureSession canAddOutput:self.videoOutput]) {
      [self.captureSession addOutput:self.videoOutput];
  }
  
  // 懒加载
  - (AVCaptureVideoDataOutput *)videoOutput {
      if (!_videoOutput) {
          _videoOutput = [[AVCaptureVideoDataOutput alloc] init];
          _videoOutput.alwaysDiscardsLateVideoFrames = YES;
          _videoOutput.videoSettings = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA]
                                                                   forKey:(id)kCVPixelBufferPixelFormatTypeKey];
      }
      return _videoOutput;
  }
  
  - (dispatch_queue_t)videoQueue {
      if (!_videoQueue) {
          _videoQueue = dispatch_queue_create("queue", DISPATCH_QUEUE_SERIAL);
      }
      return _videoQueue;
  }
  

  • 代理AVCaptureVideoDataOutputSampleBufferDelegate

  - (void)captureOutput:(AVCaptureOutput *)output didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
      @autoreleasepool {
          if (connection == [self.videoOutput connectionWithMediaType:AVMediaTypeVideo]) { // 视频
              @synchronized (self) {
                  UIImage *image = [self bufferToImage:sampleBuffer rect:self.scanView.scanRect];
                  self.uploadImg = image;
              }
          }
      }
  }

  • CMSampleBufferRef转成UIImage, 该方法有所调整，截图整张图中的某一部分，按需设置。具体获取指定区域图片需自己调整

  - (UIImage *)bufferToImage:(CMSampleBufferRef)sampleBuffer rect:(CGRect)rect {
      // Get a CMSampleBuffer's Core Video image buffer for the media data
      CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
      // Lock the base address of the pixel buffer
      CVPixelBufferLockBaseAddress(imageBuffer, 0);
  
      // Get the number of bytes per row for the pixel buffer
      void *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer);
  
      // Get the number of bytes per row for the pixel buffer
      size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
      // Get the pixel buffer width and height
      size_t width = CVPixelBufferGetWidth(imageBuffer);
      size_t height = CVPixelBufferGetHeight(imageBuffer);
  
      // Create a device-dependent RGB color space
      CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
  
      // Create a bitmap graphics context with the sample buffer data
      CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8,
                                                   bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
      // Create a Quartz image from the pixel data in the bitmap graphics context
      CGImageRef quartzImage = CGBitmapContextCreateImage(context);
      // Unlock the pixel buffer
      CVPixelBufferUnlockBaseAddress(imageBuffer,0);
  
      // Free up the context and color space
      CGContextRelease(context);
      CGColorSpaceRelease(colorSpace);
  
      // 获取指定区域图片
      CGRect dRect;
      CGSize msize = UIScreen.mainScreen.bounds.size;
      msize.height = msize.height - 150;
      CGFloat x = width * rect.origin.x / msize.width;
      CGFloat y = height * rect.origin.y / msize.height;
      CGFloat w = width * rect.size.width / msize.width;
      CGFloat h = height * rect.size.height / msize.height;
      dRect = CGRectMake(x, y, w, h);
  
      CGImageRef partRef = CGImageCreateWithImageInRect(quartzImage, dRect);
  
      // Create an image object from the Quartz image
      UIImage *image = [UIImage imageWithCGImage:partRef];
  
      // Release the Quartz image
      CGImageRelease(partRef);
      CGImageRelease(quartzImage);
  
      return image;
  }
  

• 图有了，收工。怎么用图，业务该干活了