mediapipe/docs/solutions/pose.md

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MediaPipe Pose

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Overview

Human pose estimation from video plays a critical role in various applications such as quantifying physical exercises, sign language recognition, and full-body gesture control. For example, it can form the basis for yoga, dance, and fitness applications. It can also enable the overlay of digital content and information on top of the physical world in augmented reality.

MediaPipe Pose is a ML solution for high-fidelity body pose tracking, inferring 33 3D landmarks and background segmentation mask on the whole body from RGB video frames utilizing our BlazePose research that also powers the ML Kit Pose Detection API. Current state-of-the-art approaches rely primarily on powerful desktop environments for inference, whereas our method achieves real-time performance on most modern mobile phones, desktops/laptops, in python and even on the web.

Fig 1. Example of MediaPipe Pose for pose tracking.

ML Pipeline

The solution utilizes a two-step detector-tracker ML pipeline, proven to be effective in our MediaPipe Hands and MediaPipe Face Mesh solutions. Using a detector, the pipeline first locates the person/pose region-of-interest (ROI) within the frame. The tracker subsequently predicts the pose landmarks and segmentation mask within the ROI using the ROI-cropped frame as input. Note that for video use cases the detector is invoked only as needed, i.e., for the very first frame and when the tracker could no longer identify body pose presence in the previous frame. For other frames the pipeline simply derives the ROI from the previous frame’s pose landmarks.

The pipeline is implemented as a MediaPipe graph that uses a pose landmark subgraph from the pose landmark module and renders using a dedicated pose renderer subgraph. The pose landmark subgraph internally uses a pose detection subgraph from the pose detection module.

Note: To visualize a graph, copy the graph and paste it into MediaPipe Visualizer. For more information on how to visualize its associated subgraphs, please see visualizer documentation.

Pose Estimation Quality

To evaluate the quality of our models against other well-performing publicly available solutions, we use three different validation datasets, representing different verticals: Yoga, Dance and HIIT. Each image contains only a single person located 2-4 meters from the camera. To be consistent with other solutions, we perform evaluation only for 17 keypoints from COCO topology.

Method	Yoga mAP	Yoga PCK@0.2	Dance mAP	Dance PCK@0.2	HIIT mAP	HIIT PCK@0.2
BlazePose GHUM Heavy	68.1	96.4	73.0	97.2	74.0	97.5
BlazePose GHUM Full	62.6	95.5	67.4	96.3	68.0	95.7
BlazePose GHUM Lite	45.0	90.2	53.6	92.5	53.8	93.5
AlphaPose ResNet50	63.4	96.0	57.8	95.5	63.4	96.0
Apple Vision	32.8	82.7	36.4	91.4	44.5	88.6

Fig 2. Quality evaluation in PCK@0.2.

We designed our models specifically for live perception use cases, so all of them work in real-time on the majority of modern devices.

Method	Latency Pixel 3 TFLite GPU	Latency MacBook Pro (15-inch 2017)
BlazePose GHUM Heavy	53 ms	38 ms
BlazePose GHUM Full	25 ms	27 ms
BlazePose GHUM Lite	20 ms	25 ms

Models

Person/pose Detection Model (BlazePose Detector)

The detector is inspired by our own lightweight BlazeFace model, used in MediaPipe Face Detection, as a proxy for a person detector. It explicitly predicts two additional virtual keypoints that firmly describe the human body center, rotation and scale as a circle. Inspired by Leonardo’s Vitruvian man, we predict the midpoint of a person's hips, the radius of a circle circumscribing the whole person, and the incline angle of the line connecting the shoulder and hip midpoints.

Fig 3. Vitruvian man aligned via two virtual keypoints predicted by BlazePose detector in addition to the face bounding box.

Pose Landmark Model (BlazePose GHUM 3D)

The landmark model in MediaPipe Pose predicts the location of 33 pose landmarks (see figure below).

Fig 4. 33 pose landmarks.

Optionally, MediaPipe Pose can predicts a full-body segmentation mask represented as a two-class segmentation (human or background).

Please find more detail in the BlazePose Google AI Blog, this paper, the model card and the Output section below.

Solution APIs

Cross-platform Configuration Options

Naming style and availability may differ slightly across platforms/languages.

static_image_mode

If set to false, the solution treats the input images as a video stream. It will try to detect the most prominent person in the very first images, and upon a successful detection further localizes the pose landmarks. In subsequent images, it then simply tracks those landmarks without invoking another detection until it loses track, on reducing computation and latency. If set to true, person detection runs every input image, ideal for processing a batch of static, possibly unrelated, images. Default to false.

model_complexity

Complexity of the pose landmark model: 0, 1 or 2. Landmark accuracy as well as inference latency generally go up with the model complexity. Default to 1.

smooth_landmarks

If set to true, the solution filters pose landmarks across different input images to reduce jitter, but ignored if static_image_mode is also set to true. Default to true.

enable_segmentation

If set to true, in addition to the pose landmarks the solution also generates the segmentation mask. Default to false.

smooth_segmentation

If set to true, the solution filters segmentation masks across different input images to reduce jitter. Ignored if enable_segmentation is false or static_image_mode is true. Default to true.

min_detection_confidence

Minimum confidence value ([0.0, 1.0]) from the person-detection model for the detection to be considered successful. Default to 0.5.

min_tracking_confidence

Minimum confidence value ([0.0, 1.0]) from the landmark-tracking model for the pose landmarks to be considered tracked successfully, or otherwise person detection will be invoked automatically on the next input image. Setting it to a higher value can increase robustness of the solution, at the expense of a higher latency. Ignored if static_image_mode is true, where person detection simply runs on every image. Default to 0.5.

Output

Naming style may differ slightly across platforms/languages.

pose_landmarks

A list of pose landmarks. Each landmark consists of the following:

• x and y: Landmark coordinates normalized to [0.0, 1.0] by the image width and height respectively.
• z: Represents the landmark depth with the depth at the midpoint of hips being the origin, and the smaller the value the closer the landmark is to the camera. The magnitude of z uses roughly the same scale as x.
• visibility: A value in [0.0, 1.0] indicating the likelihood of the landmark being visible (present and not occluded) in the image.

pose_world_landmarks

Fig 5. Example of MediaPipe Pose real-world 3D coordinates.

Another list of pose landmarks in world coordinates. Each landmark consists of the following:

• x, y and z: Real-world 3D coordinates in meters with the origin at the center between hips.
• visibility: Identical to that defined in the corresponding pose_landmarks.

segmentation_mask

The output segmentation mask, predicted only when enable_segmentation is set to true. The mask has the same width and height as the input image, and contains values in [0.0, 1.0] where 1.0 and 0.0 indicate high certainty of a "human" and "background" pixel respectively. Please refer to the platform-specific usage examples below for usage details.

Fig 6. Example of MediaPipe Pose segmentation mask.

Python Solution API

Please first follow general instructions to install MediaPipe Python package, then learn more in the companion Python Colab and the usage example below.

Supported configuration options:

• static_image_mode
• model_complexity
• smooth_landmarks
• enable_segmentation
• smooth_segmentation
• min_detection_confidence
• min_tracking_confidence

import cv2
import mediapipe as mp
mp_drawing = mp.solutions.drawing_utils
mp_drawing_styles = mp.solutions.drawing_styles
mp_pose = mp.solutions.pose

# For static images:
IMAGE_FILES = []
BG_COLOR = (192, 192, 192) # gray
with mp_pose.Pose(
    static_image_mode=True,
    model_complexity=2,
    enable_segmentation=True,
    min_detection_confidence=0.5) as pose:
  for idx, file in enumerate(IMAGE_FILES):
    image = cv2.imread(file)
    image_height, image_width, _ = image.shape
    # Convert the BGR image to RGB before processing.
    results = pose.process(cv2.cvtColor(image, cv2.COLOR_BGR2RGB))

    if not results.pose_landmarks:
      continue
    print(
        f'Nose coordinates: ('
        f'{results.pose_landmarks.landmark[mp_pose.PoseLandmark.NOSE].x * image_width}, '
        f'{results.pose_landmarks.landmark[mp_pose.PoseLandmark.NOSE].y * image_height})'
    )

    annotated_image = image.copy()
    # Draw segmentation on the image.
    # To improve segmentation around boundaries, consider applying a joint
    # bilateral filter to "results.segmentation_mask" with "image".
    condition = np.stack((results.segmentation_mask,) * 3, axis=-1) > 0.1
    bg_image = np.zeros(image.shape, dtype=np.uint8)
    bg_image[:] = BG_COLOR
    annotated_image = np.where(condition, annotated_image, bg_image)
    # Draw pose landmarks on the image.
    mp_drawing.draw_landmarks(
        annotated_image,
        results.pose_landmarks,
        mp_pose.POSE_CONNECTIONS,
        landmark_drawing_spec=mp_drawing_styles.get_default_pose_landmarks_style())
    cv2.imwrite('/tmp/annotated_image' + str(idx) + '.png', annotated_image)
    # Plot pose world landmarks.
    mp_drawing.plot_landmarks(
        results.pose_world_landmarks, mp_pose.POSE_CONNECTIONS)

# For webcam input:
cap = cv2.VideoCapture(0)
with mp_pose.Pose(
    min_detection_confidence=0.5,
    min_tracking_confidence=0.5) as pose:
  while cap.isOpened():
    success, image = cap.read()
    if not success:
      print("Ignoring empty camera frame.")
      # If loading a video, use 'break' instead of 'continue'.
      continue

    # To improve performance, optionally mark the image as not writeable to
    # pass by reference.
    image.flags.writeable = False
    image = cv2.cvtColor(image, cv2.COLOR_BGR2RGB)
    results = pose.process(image)

    # Draw the pose annotation on the image.
    image.flags.writeable = True
    image = cv2.cvtColor(image, cv2.COLOR_RGB2BGR)
    mp_drawing.draw_landmarks(
        image,
        results.pose_landmarks,
        mp_pose.POSE_CONNECTIONS,
        landmark_drawing_spec=mp_drawing_styles.get_default_pose_landmarks_style())
    # Flip the image horizontally for a selfie-view display.
    cv2.imshow('MediaPipe Pose', cv2.flip(image, 1))
    if cv2.waitKey(5) & 0xFF == 27:
      break
cap.release()

JavaScript Solution API

Please first see general introduction on MediaPipe in JavaScript, then learn more in the companion web demo and the following usage example.

Supported configuration options:

• modelComplexity
• smoothLandmarks
• enableSegmentation
• smoothSegmentation
• minDetectionConfidence
• minTrackingConfidence

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <script src="https://cdn.jsdelivr.net/npm/@mediapipe/camera_utils/camera_utils.js" crossorigin="anonymous"></script>
  <script src="https://cdn.jsdelivr.net/npm/@mediapipe/control_utils/control_utils.js" crossorigin="anonymous"></script>
  <script src="https://cdn.jsdelivr.net/npm/@mediapipe/control_utils_3d/control_utils_3d.js" crossorigin="anonymous"></script>
  <script src="https://cdn.jsdelivr.net/npm/@mediapipe/drawing_utils/drawing_utils.js" crossorigin="anonymous"></script>
  <script src="https://cdn.jsdelivr.net/npm/@mediapipe/pose/pose.js" crossorigin="anonymous"></script>
</head>

<body>
  <div class="container">
    <video class="input_video"></video>
    <canvas class="output_canvas" width="1280px" height="720px"></canvas>
    <div class="landmark-grid-container"></div>
  </div>
</body>
</html>

<script type="module">
const videoElement = document.getElementsByClassName('input_video')[0];
const canvasElement = document.getElementsByClassName('output_canvas')[0];
const canvasCtx = canvasElement.getContext('2d');
const landmarkContainer = document.getElementsByClassName('landmark-grid-container')[0];
const grid = new LandmarkGrid(landmarkContainer);

function onResults(results) {
  if (!results.poseLandmarks) {
    grid.updateLandmarks([]);
    return;
  }

  canvasCtx.save();
  canvasCtx.clearRect(0, 0, canvasElement.width, canvasElement.height);
  canvasCtx.drawImage(results.segmentationMask, 0, 0,
                      canvasElement.width, canvasElement.height);

  // Only overwrite existing pixels.
  canvasCtx.globalCompositeOperation = 'source-in';
  canvasCtx.fillStyle = '#00FF00';
  canvasCtx.fillRect(0, 0, canvasElement.width, canvasElement.height);

  // Only overwrite missing pixels.
  canvasCtx.globalCompositeOperation = 'destination-atop';
  canvasCtx.drawImage(
      results.image, 0, 0, canvasElement.width, canvasElement.height);

  canvasCtx.globalCompositeOperation = 'source-over';
  drawConnectors(canvasCtx, results.poseLandmarks, POSE_CONNECTIONS,
                 {color: '#00FF00', lineWidth: 4});
  drawLandmarks(canvasCtx, results.poseLandmarks,
                {color: '#FF0000', lineWidth: 2});
  canvasCtx.restore();

  grid.updateLandmarks(results.poseWorldLandmarks);
}

const pose = new Pose({locateFile: (file) => {
  return `https://cdn.jsdelivr.net/npm/@mediapipe/pose/${file}`;
}});
pose.setOptions({
  modelComplexity: 1,
  smoothLandmarks: true,
  enableSegmentation: true,
  smoothSegmentation: true,
  minDetectionConfidence: 0.5,
  minTrackingConfidence: 0.5
});
pose.onResults(onResults);

const camera = new Camera(videoElement, {
  onFrame: async () => {
    await pose.send({image: videoElement});
  },
  width: 1280,
  height: 720
});
camera.start();
</script>

Example Apps

Please first see general instructions for Android, iOS, and desktop on how to build MediaPipe examples.

Note: To visualize a graph, copy the graph and paste it into MediaPipe Visualizer. For more information on how to visualize its associated subgraphs, please see visualizer documentation.

Mobile

Main Example

• Graph: mediapipe/graphs/pose_tracking/pose_tracking_gpu.pbtxt
• Android target: (or download prebuilt ARM64 APK) mediapipe/examples/android/src/java/com/google/mediapipe/apps/posetrackinggpu:posetrackinggpu
• iOS target: mediapipe/examples/ios/posetrackinggpu:PoseTrackingGpuApp

Desktop

Please first see general instructions for desktop on how to build MediaPipe examples.

Main Example

• Running on CPU
  • Graph: mediapipe/graphs/pose_tracking/pose_tracking_cpu.pbtxt
  • Target: mediapipe/examples/desktop/pose_tracking:pose_tracking_cpu
• Running on GPU
  • Graph: mediapipe/graphs/pose_tracking/pose_tracking_gpu.pbtxt
  • Target: mediapipe/examples/desktop/pose_tracking:pose_tracking_gpu

Resources

• Google AI Blog: BlazePose - On-device Real-time Body Pose Tracking
• Paper: BlazePose: On-device Real-time Body Pose Tracking (presentation)
• Models and model cards
• GHUM & GHUML: Generative 3D Human Shape and Articulated Pose Models
• Web demo
• Python Colab