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Visualization

MMSegmentation 1.x provides convenient ways for monitoring training status or visualizing data and model predictions.

Training status Monitor

MMSegmentation 1.x uses TensorBoard to monitor training status.

TensorBoard Configuration

Install TensorBoard following official instructions e.g.

pip install tensorboardX
pip install future tensorboard

Add TensorboardVisBackend in vis_backend of visualizer in default_runtime.py config file:

vis_backends = [dict(type='LocalVisBackend'),
                dict(type='TensorboardVisBackend')]
visualizer = dict(
    type='SegLocalVisualizer', vis_backends=vis_backends, name='visualizer')

Examining scalars in TensorBoard

Launch training experiment e.g.

python tools/train.py configs/pspnet/pspnet_r50-d8_4xb4-80k_ade20k-512x512.py --work-dir work_dir/test_visual

Find the vis_data path of work_dir after starting training, for example, the vis_data path of this particular test is as follows:

work_dirs/test_visual/20220810_115248/vis_data

The scalar file in vis_data path includes learning rate, losses and data_time etc, also record metrics results and you can refer logging tutorial in MMEngine to log custom data. The tensorboard visualization results are executed with the following command:

tensorboard --logdir work_dirs/test_visual/20220810_115248/vis_data

Data and Results visualization

Visualizer Data Samples during Model Testing or Validation

MMSegmentation provides SegVisualizationHook which is a hook working to visualize ground truth and prediction of segmentation during model testing and evaluation. Its configuration is in default_hooks, please see Runner tutorial for more details.

For example, In _base_/schedules/schedule_20k.py, modify the SegVisualizationHook configuration, set draw to True to enable the storage of network inference results, interval indicates the sampling interval of the prediction results, and when set to 1, each inference result of the network will be saved. interval is set to 50 by default:

default_hooks = dict(
    timer=dict(type='IterTimerHook'),
    logger=dict(type='LoggerHook', interval=50, log_metric_by_epoch=False),
    param_scheduler=dict(type='ParamSchedulerHook'),
    checkpoint=dict(type='CheckpointHook', by_epoch=False, interval=2000),
    sampler_seed=dict(type='DistSamplerSeedHook'),
    visualization=dict(type='SegVisualizationHook', draw=True, interval=1))

After launch training experiment, visualization results will be stored in the local folder in validation loop, or when launch evaluation a model on one dataset, the prediction results will be store in the local. The stored results of the local visualization are kept in vis_image under $WORK_DIRS/vis_data, e.g.:

work_dirs/test_visual/20220810_115248/vis_data/vis_image

In addition, if TensorboardVisBackend is add in vis_backends, like above, we can also run the following command to view them in TensorBoard:

tensorboard --logdir work_dirs/test_visual/20220810_115248/vis_data

Visualize a Single Data Sample

If you want to visualize a single data sample, we suggest to use SegLocalVisualizer.

SegLocalVisualizer is child class inherits from Visualizer in MMEngine and works for MMSegmentation visualization, for more details about Visualizer please refer to visualization tutorial in MMEngine.

Here is an example about SegLocalVisualizer, first you may download example data below by following commands:

wget https://user-images.githubusercontent.com/24582831/189833109-eddad58f-f777-4fc0-b98a-6bd429143b06.png --output-document aachen_000000_000019_leftImg8bit.png
wget https://user-images.githubusercontent.com/24582831/189833143-15f60f8a-4d1e-4cbb-a6e7-5e2233869fac.png --output-document aachen_000000_000019_gtFine_labelTrainIds.png

Then you can find their local path and use the scripts below to visualize:

import mmcv
import os.path as osp
import torch
# `PixelData` is data structure for pixel-level annotations or predictions defined in MMEngine.
# Please refer to below tutorial file of data structures in MMEngine:
# https://github.com/open-mmlab/mmengine/tree/main/docs/en/advanced_tutorials/data_element.md

from mmengine.structures import PixelData

# `SegDataSample` is data structure interface between different components
# defined in MMSegmentation, it includes ground truth, prediction and
# predicted logits of semantic segmentation.
# Please refer to below tutorial file of `SegDataSample` for more details:
# https://github.com/open-mmlab/mmsegmentation/blob/1.x/docs/en/advanced_guides/structures.md

from mmseg.structures import SegDataSample
from mmseg.visualization import SegLocalVisualizer

out_file = 'out_file_cityscapes'
save_dir = './work_dirs'

image = mmcv.imread(
    osp.join(
        osp.dirname(__file__),
        './aachen_000000_000019_leftImg8bit.png'
    ),
    'color')
sem_seg = mmcv.imread(
    osp.join(
        osp.dirname(__file__),
        './aachen_000000_000019_gtFine_labelTrainIds.png'  # noqa
    ),
    'unchanged')
sem_seg = torch.from_numpy(sem_seg)
gt_sem_seg_data = dict(data=sem_seg)
gt_sem_seg = PixelData(**gt_sem_seg_data)
data_sample = SegDataSample()
data_sample.gt_sem_seg = gt_sem_seg

seg_local_visualizer = SegLocalVisualizer(
    vis_backends=[dict(type='LocalVisBackend')],
    save_dir=save_dir)

# The meta information of dataset usually includes `classes` for class names and
# `palette` for visualization color of each foreground.
# All class names and palettes are defined in the file:
# https://github.com/open-mmlab/mmsegmentation/blob/1.x/mmseg/utils/class_names.py

seg_local_visualizer.dataset_meta = dict(
    classes=('road', 'sidewalk', 'building', 'wall', 'fence',
             'pole', 'traffic light', 'traffic sign',
             'vegetation', 'terrain', 'sky', 'person', 'rider',
             'car', 'truck', 'bus', 'train', 'motorcycle',
             'bicycle'),
    palette=[[128, 64, 128], [244, 35, 232], [70, 70, 70],
             [102, 102, 156], [190, 153, 153], [153, 153, 153],
             [250, 170, 30], [220, 220, 0], [107, 142, 35],
             [152, 251, 152], [70, 130, 180], [220, 20, 60],
             [255, 0, 0], [0, 0, 142], [0, 0, 70],
             [0, 60, 100], [0, 80, 100], [0, 0, 230],
             [119, 11, 32]])
# When `show=True`, the results would be shown directly,
# else if `show=False`, the results would be saved in local directory folder.
seg_local_visualizer.add_datasample(out_file, image,
                                    data_sample, show=False)

Then the visualization result of image with its corresponding ground truth could be found in ./work_dirs/vis_data/vis_image/ whose name is out_file_cityscapes_0.png:

If you would like to know more visualization usage, you can refer to visualization tutorial in MMEngine.