Face Blur App

This is an app to demonstrate the use of VisionCamera to build a realtime face blurring application. 😷

https://github.com/mrousavy/FaceBlurApp/assets/15199031/cb2fd119-9dad-4e8a-9a97-579bb2eae888

It took me 25 minutes to build the app, and this runs on both iOS and Android at 60-120 FPS. I can swap out the drawing algorithm, plug in a different shader, use a different ML model like pose-, object- or hand-detection, and change Camera properties within seconds to minutes - it has never been so easy to build Camera apps, all thanks to react-native-vision-camera! 🚀

How?

FaceBlurApp uses react-native-vision-camera to display a Camera feed.

Using the VisionCamera Frame Processors API and the react-native-vision-camera-face-detector Frame Processor plugin, we can detect faces in realtime at 60-120 FPS.

Then, we can draw a blur shader/mask over the detected faces by using the VisionCamera Skia Frame Processors integration. In this case, a simple blur ImageFilter from react-native-skia is used.

This is the relevant code:

const {detectFaces} = useFaceDetector({
   performanceMode: 'fast',
   contourMode: 'all',
   landmarkMode: 'none',
   classificationMode: 'none',
});

const blurRadius = 25;
const blurFilter = Skia.ImageFilter.MakeBlur(
   blurRadius,
   blurRadius,
   TileMode.Repeat,
   null,
);
const paint = Skia.Paint();
paint.setImageFilter(blurFilter);

const frameProcessor = useSkiaFrameProcessor(frame => {
   'worklet';
   // 1. Render frame as it is
   frame.render();

   // 2. Detect faces in frame
   const {faces} = detectFaces({frame: frame});

   // 3. Draw a blur mask over each face
   for (const face of faces) {
      const path = Skia.Path.Make();

      const necessaryContours: (keyof Contours)[] = [
         'FACE',
         'LEFT_CHEEK',
         'RIGHT_CHEEK',
      ];
      for (const key of necessaryContours) {
         const points = face.contours[key];
         points.forEach((point, index) => {
            if (index === 0) {
               // it's a starting point
               path.moveTo(point.x, point.y);
            } else {
               // it's a continuation
               path.lineTo(point.x, point.y);
            }
         });
         path.close();
      }

      frame.save();
      frame.clipPath(path, ClipOp.Intersect, true);
      frame.render(paint);
      frame.restore();
   }
}, [paint, detectFaces])

See App.tsx for the full code.

How's the Performance?

If you know me you know that my libs are always really fast. This is no exception:

• Frame Processors are built almost entirely with C++ to run Frame analysis with almost zero overhead.
• Frame Processors run in Worklets on a separate Thread, so they are not interrupted by JS lags.
• The MLKit models are built with native code and use GPU-acceleration
• VisionCamera can provide either yuv or efficiently converted rgb buffers for faster ML execution
• VisionCamera supports GPU buffer compression