pragma mark 获取扫描到的图片

• (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
  {
  // 通过抽样缓存数据创建一个UIImage对象
  self.zoomedImage = [self imageFromSampleBuffer:sampleBuffer fromConnection:connection];
  }
  // 通过抽样缓存数据创建一个UIImage对象

• (UIImage *) imageFromSampleBuffer:(CMSampleBufferRef) sampleBuffer fromConnection:(AVCaptureConnection *)connection
  {

  // 为媒体数据设置一个CMSampleBuffer的Core Video图像缓存对象
  CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
  // 锁定pixel buffer的基地址
  CVPixelBufferLockBaseAddress(imageBuffer, 0);

  // 得到pixel buffer的基地址
  uint8_t *baseAddress = (uint8_t *)CVPixelBufferGetBaseAddress(imageBuffer);

  // 得到pixel buffer的行字节数
  size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
  // 得到pixel buffer的宽和高
  size_t width = CVPixelBufferGetWidth(imageBuffer);
  size_t height = CVPixelBufferGetHeight(imageBuffer);

  // 创建一个依赖于设备的RGB颜色空间
  CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

  // 用抽样缓存的数据创建一个位图格式的图形上下文（graphics context）对象
  CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8,
  bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
  // 根据这个位图context中的像素数据创建一个Quartz image对象
  CGImageRef quartzImage = CGBitmapContextCreateImage(context);
  // 解锁pixel buffer
  CVPixelBufferUnlockBaseAddress(imageBuffer,0);

  // 释放context和颜色空间
  CGContextRelease(context);
  CGColorSpaceRelease(colorSpace);

  CGRect zoom = CGRectMake(0, 0,930,930);
  CGImageRef newImage2 = CGImageCreateWithImageInRect(quartzImage, zoom);
  // 用Quartz image创建一个UIImage对象image
  UIImage *image = [UIImage imageWithCGImage:newImage2 scale: 1.0f orientation: UIImageOrientationRight];

  // 释放Quartz image对象
  CGImageRelease(quartzImage);
  CGImageRelease(newImage2);
  return (image);
  }