如何在使用 react-native-firebase-mlkit 视觉使用 OCR 处理图像后绘制边界框

Question

我已成功检测到使用 react-native-camera 拍摄的图像上的文本元素。在vision().textRecognizerProcessImage(photoUri)成功返回检测到的文本。

// take the photo from the camera
  takePicture = async () => {
    try {
      const options = {
        quality: 0.8,
        base64: true,
        skipProcessing: true,
      };
      const picture = await this.camera.takePictureAsync(options);
      console.log('picture', picture);
      const {uri, width, height} = picture;
      // saving the pixel size of the selected image too 
      // for boxes position/size calculation
      this.setState({
        photoUri: uri,
        imgPixelHeight: height,
        imgPixelWidth: width,
      });
    } catch (e) {
      console.warn(e);
    }
  };

// processing the image to detect text
  processImage = async () => {
    const {photoUri} = this.state;
    console.log('processing Image...');
    vision()
      .textRecognizerProcessImage(photoUri)
      .then(result => {
        console.log('processImage response', result);
        this.displayProcessResult(result);
      })
      .catch(error => {
        console.log('process error', error);
      });
  };

// setting the elements
  displayProcessResult(result) {
    const textElements = this.getElements(result);
    this.setState({displayRectangles: true, textElements}, () => {
      console.log('my new state', this.state);
    });
  }

// getting only the elements objects from mlkit vision
  getElements(result) {
    let allElements = [];
    const {blocks} = result;
    blocks.forEach(block => {
      const {lines} = block;
      lines.forEach(line => {
        const {elements} = line;
        allElements = [...allElements, ...elements];
      });
    });

    console.log('displayProcessResult response', allElements);

    return allElements;
  }

// drawing the boxes aronund the detected text elements
  drawRectangles() {
    const {textElements} = this.state;
    return textElements.map((element, index) => this.drawBox(element, index));
  }

  drawBox = (e, i) => {
    let [left, top, right, bottom] = e.boundingBox;
    const {imageWidh, imageHeight, imgPixelWidth, imgPixelHeight} = this.state;

    // calculating the absolute position of each box base on the pixel size of the 
    // of the image and the on screen sizes (imageWidh, imageHeight) given by react native 
    // (check the renderCameraOrImage funtion) 

    left = (left / imgPixelWidth) * imageWidh;
    right = (right / imgPixelWidth) * imageWidh;
    top = (top / imgPixelHeight) * imageHeight;
    bottom = (bottom / imgPixelHeight) * imageHeight;

    const boxWidth = Math.abs(left - right);
    const boxHeight = Math.abs(top - bottom);

    console.log('box', boxWidth, boxHeight);

    return (
      <TouchableOpacity
        key={i}
        style={{
          position: 'absolute',
          left,
          top,
          width: boxWidth,
          height: boxHeight,
          borderWidth: 1,
          borderColor: Colors.green,
          zIndex: 2000,
        }}
      />
    );
  };

// rendering the image or the camera base on the photoUri definition in the state
  renderCameraOrImage() {
    // render cam or img
    const {photoUri} = this.state;
    return (
      <View>
        {!photoUri ? (
          <RNCamera
            ref={ref => {
              this.camera = ref;
            }}
            style={styles.camera}
            type={RNCamera.Constants.Type.back}
            flashMode={RNCamera.Constants.FlashMode.off}
            androidCameraPermissionOptions={{
              title: 'Permission to use camera',
              message: 'We need your permission to use your camera',
              buttonPositive: 'Ok',
              buttonNegative: 'Cancel',
            }}
            zoom={this.state.zoomValue}
          />
        ) : (
          <Image
            source={{uri: this.state.photoUri}}
            style={styles.camera}
            onLayout={event => {
              var {x, y, width, height} = event.nativeEvent.layout;
              this.setState({imageWidh: width, imageHeight: height});
            }}
          />
        )}
      </View>
    );
  }

由于绘制的框已关闭，我得到的结果并不令人满意：

我需要帮助来定义更好的方法，以便将框正确定位在文本元素上