cityscapes.py

# Copyright (c) OpenMMLab. All rights reserved.
import argparse
import glob
import os.path as osp

import cityscapesscripts.helpers.labels as CSLabels
import mmcv
import numpy as np
import pycocotools.mask as maskUtils
from mmengine.fileio import dump
from mmengine.utils import (Timer, mkdir_or_exist, track_parallel_progress,
                            track_progress)


def collect_files(img_dir, gt_dir):
    suffix = 'leftImg8bit.png'
    files = []
    for img_file in glob.glob(osp.join(img_dir, '**/*.png')):
        assert img_file.endswith(suffix), img_file
        inst_file = gt_dir + img_file[
            len(img_dir):-len(suffix)] + 'gtFine_instanceIds.png'
        # Note that labelIds are not converted to trainId for seg map
        segm_file = gt_dir + img_file[
            len(img_dir):-len(suffix)] + 'gtFine_labelIds.png'
        files.append((img_file, inst_file, segm_file))
    assert len(files), f'No images found in {img_dir}'
    print(f'Loaded {len(files)} images from {img_dir}')

    return files


def collect_annotations(files, nproc=1):
    print('Loading annotation images')
    if nproc > 1:
        images = track_parallel_progress(load_img_info, files, nproc=nproc)
    else:
        images = track_progress(load_img_info, files)

    return images


def load_img_info(files):
    img_file, inst_file, segm_file = files
    inst_img = mmcv.imread(inst_file, 'unchanged')
    # ids < 24 are stuff labels (filtering them first is about 5% faster)
    unique_inst_ids = np.unique(inst_img[inst_img >= 24])
    anno_info = []
    for inst_id in unique_inst_ids:
        # For non-crowd annotations, inst_id // 1000 is the label_id
        # Crowd annotations have <1000 instance ids
        label_id = inst_id // 1000 if inst_id >= 1000 else inst_id
        label = CSLabels.id2label[label_id]
        if not label.hasInstances or label.ignoreInEval:
            continue

        category_id = label.id
        iscrowd = int(inst_id < 1000)
        mask = np.asarray(inst_img == inst_id, dtype=np.uint8, order='F')
        mask_rle = maskUtils.encode(mask[:, :, None])[0]

        area = maskUtils.area(mask_rle)
        # convert to COCO style XYWH format
        bbox = maskUtils.toBbox(mask_rle)

        # for json encoding
        mask_rle['counts'] = mask_rle['counts'].decode()

        anno = dict(
            iscrowd=iscrowd,
            category_id=category_id,
            bbox=bbox.tolist(),
            area=area.tolist(),
            segmentation=mask_rle)
        anno_info.append(anno)
    video_name = osp.basename(osp.dirname(img_file))
    img_info = dict(
        # remove img_prefix for filename
        file_name=osp.join(video_name, osp.basename(img_file)),
        height=inst_img.shape[0],
        width=inst_img.shape[1],
        anno_info=anno_info,
        segm_file=osp.join(video_name, osp.basename(segm_file)))

    return img_info


def cvt_annotations(image_infos, out_json_name):
    out_json = dict()
    img_id = 0
    ann_id = 0
    out_json['images'] = []
    out_json['categories'] = []
    out_json['annotations'] = []
    for image_info in image_infos:
        image_info['id'] = img_id
        anno_infos = image_info.pop('anno_info')
        out_json['images'].append(image_info)
        for anno_info in anno_infos:
            anno_info['image_id'] = img_id
            anno_info['id'] = ann_id
            out_json['annotations'].append(anno_info)
            ann_id += 1
        img_id += 1
    for label in CSLabels.labels:
        if label.hasInstances and not label.ignoreInEval:
            cat = dict(id=label.id, name=label.name)
            out_json['categories'].append(cat)

    if len(out_json['annotations']) == 0:
        out_json.pop('annotations')

    dump(out_json, out_json_name)
    return out_json


def parse_args():
    parser = argparse.ArgumentParser(
        description='Convert Cityscapes annotations to COCO format')
    parser.add_argument('cityscapes_path', help='cityscapes data path')
    parser.add_argument('--img-dir', default='leftImg8bit', type=str)
    parser.add_argument('--gt-dir', default='gtFine', type=str)
    parser.add_argument('-o', '--out-dir', help='output path')
    parser.add_argument(
        '--nproc', default=1, type=int, help='number of process')
    args = parser.parse_args()
    return args


def main():
    args = parse_args()
    cityscapes_path = args.cityscapes_path
    out_dir = args.out_dir if args.out_dir else cityscapes_path
    mkdir_or_exist(out_dir)

    img_dir = osp.join(cityscapes_path, args.img_dir)
    gt_dir = osp.join(cityscapes_path, args.gt_dir)

    set_name = dict(
        train='instancesonly_filtered_gtFine_train.json',
        val='instancesonly_filtered_gtFine_val.json',
        test='instancesonly_filtered_gtFine_test.json')

    for split, json_name in set_name.items():
        print(f'Converting {split} into {json_name}')
        with Timer(print_tmpl='It took {}s to convert Cityscapes annotation'):
            files = collect_files(
                osp.join(img_dir, split), osp.join(gt_dir, split))
            image_infos = collect_annotations(files, nproc=args.nproc)
            cvt_annotations(image_infos, osp.join(out_dir, json_name))


if __name__ == '__main__':
    main()