[Feature] Add demo script for 3d hand pose

demo/docs/en/3d_hand_demo.md

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+## 3D Hand Demo
+
+<img src="https://user-images.githubusercontent.com/28900607/121288285-b8fcbf00-c915-11eb-98e4-ba846de12987.gif" width="600px" alt><br>
+
+### 3D Hand Estimation Image Demo
+
+#### Using gt hand bounding boxes as input
+
+We provide a demo script to test a single image, given gt json file.
+
+```shell
+python demo/hand3d_internet_demo.py \
+    ${MMPOSE_CONFIG_FILE} ${MMPOSE_CHECKPOINT_FILE} \
+    --input ${INPUT_FILE} \
+    --output-root ${OUTPUT_ROOT} \
+    [--save-predictions] \
+    [--gt-joints-file ${GT_JOINTS_FILE}]\
+    [--disable-rebase-keypoint] \
+    [--show] \
+    [--device ${GPU_ID or CPU}] \
+    [--kpt-thr ${KPT_THR}] \
+    [--show-kpt-idx] \
+    [--radius ${RADIUS}] \
+    [--thickness ${THICKNESS}]
+```
+
+The pre-trained hand pose estimation model can be downloaded from [model zoo](https://mmpose.readthedocs.io/en/latest/model_zoo/hand_3d_keypoint.html).
+Take [internet model](https://download.openmmlab.com/mmpose/hand3d/internet/res50_intehand3dv1.0_all_256x256-42b7f2ac_20210702.pth) as an example:
+
+```shell
+python demo/hand3d_internet_demo.py \
+    configs/hand_3d_keypoint/internet/interhand3d/internet_res50_4xb16-20e_interhand3d-256x256.py \
+    https://download.openmmlab.com/mmpose/hand3d/internet/res50_intehand3dv1.0_all_256x256-42b7f2ac_20210702.pth \
+    --input tests/data/interhand2.6m/image69148.jpg \
+    --save-predictions \
+    --output-root vis_results
+```

demo/hand3d_internet_demo.py

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+# Copyright (c) OpenMMLab. All rights reserved.
+import logging
+import mimetypes
+import os
+import time
+from argparse import ArgumentParser
+
+import cv2
+import json_tricks as json
+import mmcv
+import mmengine
+import numpy as np
+from mmengine.logging import print_log
+
+from mmpose.apis import inference_topdown, init_model
+from mmpose.registry import VISUALIZERS
+from mmpose.structures import (PoseDataSample, merge_data_samples,
+                               split_instances)
+
+
+def parse_args():
+    parser = ArgumentParser()
+    parser.add_argument('config', help='Config file')
+    parser.add_argument('checkpoint', help='Checkpoint file')
+    parser.add_argument(
+        '--input', type=str, default='', help='Image/Video file')
+    parser.add_argument(
+        '--output-root',
+        type=str,
+        default='',
+        help='root of the output img file. '
+        'Default not saving the visualization images.')
+    parser.add_argument(
+        '--save-predictions',
+        action='store_true',
+        default=False,
+        help='whether to save predicted results')
+    parser.add_argument(
+        '--disable-rebase-keypoint',
+        action='store_true',
+        default=False,
+        help='Whether to disable rebasing the predicted 3D pose so its '
+        'lowest keypoint has a height of 0 (landing on the ground). Rebase '
+        'is useful for visualization when the model do not predict the '
+        'global position of the 3D pose.')
+    parser.add_argument(
+        '--show',
+        action='store_true',
+        default=False,
+        help='whether to show result')
+    parser.add_argument('--device', default='cpu', help='Device for inference')
+    parser.add_argument(
+        '--kpt-thr',
+        type=float,
+        default=0.3,
+        help='Visualizing keypoint thresholds')
+    parser.add_argument(
+        '--show-kpt-idx',
+        action='store_true',
+        default=False,
+        help='Whether to show the index of keypoints')
+    parser.add_argument(
+        '--radius',
+        type=int,
+        default=3,
+        help='Keypoint radius for visualization')
+    parser.add_argument(
+        '--thickness',
+        type=int,
+        default=1,
+        help='Link thickness for visualization')
+
+    args = parser.parse_args()
+    return args
+
+
+def process_one_image(args, img, model, visualizer=None, show_interval=0):
+    """Visualize predicted keypoints of one image."""
+    # inference a single image
+    pose_results = inference_topdown(model, img)
+    # post-processing
+    pose_results_2d = []
+    for idx, res in enumerate(pose_results):
+        pred_instances = res.pred_instances
+        keypoints = pred_instances.keypoints
+        rel_root_depth = pred_instances.rel_root_depth
+        scores = pred_instances.keypoint_scores
+        hand_type = pred_instances.hand_type
+
+        res_2d = PoseDataSample()
+        gt_instances = res.gt_instances.clone()
+        pred_instances = pred_instances.clone()
+        res_2d.gt_instances = gt_instances
+        res_2d.pred_instances = pred_instances
+
+        # add relative root depth to left hand joints
+        keypoints[:, 21:, 2] += rel_root_depth
+
+        # set joint scores according to hand type
+        scores[:, :21] *= hand_type[:, [0]]
+        scores[:, 21:] *= hand_type[:, [1]]
+        # normalize kpt score
+        if scores.max() > 1:
+            scores /= 255
+
+        res_2d.pred_instances.set_field(keypoints[..., :2].copy(), 'keypoints')
+
+        # rotate the keypoint to make z-axis correspondent to height
+        # for better visualization
+        vis_R = np.array([[1, 0, 0], [0, 0, -1], [0, 1, 0]])
+        keypoints[..., :3] = keypoints[..., :3] @ vis_R
+
+        # rebase height (z-axis)
+        if not args.disable_rebase_keypoint:
+            valid = scores > 0
+            keypoints[..., 2] -= np.min(
+                keypoints[valid, 2], axis=-1, keepdims=True)
+
+        pose_results[idx].pred_instances.keypoints = keypoints
+        pose_results[idx].pred_instances.keypoint_scores = scores
+        pose_results_2d.append(res_2d)
+
+    data_samples = merge_data_samples(pose_results)
+    data_samples_2d = merge_data_samples(pose_results_2d)
+
+    # show the results
+    if isinstance(img, str):
+        img = mmcv.imread(img, channel_order='rgb')
+    elif isinstance(img, np.ndarray):
+        img = mmcv.bgr2rgb(img)
+
+    if visualizer is not None:
+        visualizer.add_datasample(
+            'result',
+            img,
+            data_sample=data_samples,
+            det_data_sample=data_samples_2d,
+            draw_gt=False,
+            draw_bbox=True,
+            kpt_thr=args.kpt_thr,
+            convert_keypoint=False,
+            axis_azimuth=-115,
+            axis_limit=200,
+            axis_elev=15,
+            show_kpt_idx=args.show_kpt_idx,
+            show=args.show,
+            wait_time=show_interval)
+
+    # if there is no instance detected, return None
+    return data_samples.get('pred_instances', None)
+
+
+def main():
+    args = parse_args()
+
+    assert args.input != ''
+    assert args.show or (args.output_root != '')
+
+    output_file = None
+    if args.output_root:
+        mmengine.mkdir_or_exist(args.output_root)
+        output_file = os.path.join(args.output_root,
+                                   os.path.basename(args.input))
+        if args.input == 'webcam':
+            output_file += '.mp4'
+
+    if args.save_predictions:
+        assert args.output_root != ''
+        args.pred_save_path = f'{args.output_root}/results_' \
+            f'{os.path.splitext(os.path.basename(args.input))[0]}.json'
+
+    # build the model from a config file and a checkpoint file
+    model = init_model(args.config, args.checkpoint, device=args.device)
+
+    # init visualizer
+    model.cfg.visualizer.radius = args.radius
+    model.cfg.visualizer.line_width = args.thickness
+
+    visualizer = VISUALIZERS.build(model.cfg.visualizer)
+    visualizer.set_dataset_meta(model.dataset_meta)
+
+    if args.input == 'webcam':
+        input_type = 'webcam'
+    else:
+        input_type = mimetypes.guess_type(args.input)[0].split('/')[0]
+
+    if input_type == 'image':
+        # inference
+        pred_instances = process_one_image(args, args.input, model, visualizer)
+
+        if args.save_predictions:
+            pred_instances_list = split_instances(pred_instances)
+
+        if output_file:
+            img_vis = visualizer.get_image()
+            mmcv.imwrite(mmcv.rgb2bgr(img_vis), output_file)
+
+    elif input_type in ['webcam', 'video']:
+
+        if args.input == 'webcam':
+            cap = cv2.VideoCapture(0)
+        else:
+            cap = cv2.VideoCapture(args.input)
+
+        video_writer = None
+        pred_instances_list = []
+        frame_idx = 0
+
+        while cap.isOpened():
+            success, frame = cap.read()
+            frame_idx += 1
+
+            if not success:
+                break
+
+            # topdown pose estimation
+            pred_instances = process_one_image(args, frame, model, visualizer,
+                                               0.001)
+
+            if args.save_predictions:
+                # save prediction results
+                pred_instances_list.append(
+                    dict(
+                        frame_id=frame_idx,
+                        instances=split_instances(pred_instances)))
+
+            # output videos
+            if output_file:
+                frame_vis = visualizer.get_image()
+
+                if video_writer is None:
+                    fourcc = cv2.VideoWriter_fourcc(*'mp4v')
+                    # the size of the image with visualization may vary
+                    # depending on the presence of heatmaps
+                    video_writer = cv2.VideoWriter(
+                        output_file,
+                        fourcc,
+                        25,  # saved fps
+                        (frame_vis.shape[1], frame_vis.shape[0]))
+
+                video_writer.write(mmcv.rgb2bgr(frame_vis))
+
+            if args.show:
+                # press ESC to exit
+                if cv2.waitKey(5) & 0xFF == 27:
+                    break
+
+                time.sleep(args.show_interval)
+
+        if video_writer:
+            video_writer.release()
+
+        cap.release()
+
+    else:
+        args.save_predictions = False
+        raise ValueError(
+            f'file {os.path.basename(args.input)} has invalid format.')
+
+    if args.save_predictions:
+        with open(args.pred_save_path, 'w') as f:
+            json.dump(
+                dict(
+                    meta_info=model.dataset_meta,
+                    instance_info=pred_instances_list),
+                f,
+                indent='\t')
+        print(f'predictions have been saved at {args.pred_save_path}')
+
+    if output_file is not None:
+        input_type = input_type.replace('webcam', 'video')
+        print_log(
+            f'the output {input_type} has been saved at {output_file}',
+            logger='current',
+            level=logging.INFO)
+
+
+if __name__ == '__main__':
+    main()