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Training Detection Network with Custom Datasets

This document provides tutorials on how to train text detection networks using custom datasets.

1. Dataset preperation

Currently, MindOCR detection network supports two input formats, namely

  • Common Dataset：A file format that stores images, text bounding boxes, and transcriptions. An example of the target file format is:
img_1.jpg\t[{"transcription": "MASA", "points": [[310, 104], [416, 141], [418, 216], [312, 179]]}, {...}]

It is read by DetDataset. If your dataset is not in the same format as the example format, see instructions on how convert different datasets' annotations into the supported format.

  • SynthTextDataset: A file format provided by SynthText800k. More details about this dataset can be found here. The annotation file is a .mat file consisting of imnames(image names), wordBB(word-level bounding-boxes), charBB(character-level bounding boxes), and txt (text strings). It is read by SynthTextDataset. Users can take SynthTextDataset as a reference to write their custom dataset class.

We recommend users to prepare text detection datasets in the Common Dataset format, and then use DetDataset to load the data. The following tutorials further explain on the detailed steps.

1.1 Preparing Training Data

Please place all training images in a single folder, and specify a txt file train_det.txt at a higher directory to label all training image names and corresponding labels. An example of the txt file is as follows:

# File Name	# A list of dictionaries
img_1.jpg\t[{"transcription": "Genaxis Theatre", "points": [[377, 117], [463, 117], [465, 130], [378, 130]]}, {"transcription": "[06]", "points": [[493, 115], [519, 115], [519, 131], [493, 131]]}, {...}]
img_2.jpg\t[{"transcription": "guardian", "points": [[642, 250], [769, 230], [775, 255], [648, 275]]}]
...

Note: Please separate image names and labels using \tab, and avoid using spaces or other delimiters.

The final training set will be stored in the following format:

|-data
    |- train_det.txt
    |- training
        |- img_1.jpg
        |- img_2.jpg
        |- img_3.jpg
        | ...

1.2 Preparing Validation Data

Similarly, please place all validation images in a single folder, and specify a txt file val_det.txt at a higher directory to label all validation image names and corresponding labels. The final validation set will be stored in the following format:

|-data
    |- val_det.txt
    |- validation
        |- img_1.jpg
        |- img_2.jpg
        |- img_3.jpg
        | ...

2. Configuration File Preperation

To prepare the corresponding configuration file, users should specify the directories for the training and validation datasets.

2.1 Configure train/validation datasets

Please select configs/det/dbnet/db_r50_icdar15.yaml as the initial configuration file and modify the train.dataset and eval.dataset fields in it.

...
train:
  ...
  dataset:
    type: DetDataset                                                  # File reading method. Here we use the `Common Dataset` format
    dataset_root: dir/to/data/                                        # Root directory of the data
    data_dir: training/                                               # Training dataset directory. It will be concatenated with `dataset_root` to form a complete path.
    label_file: train_det.txt                                       # Path of the training label. It will be concatenated with `dataset_root` to form a complete path.
...
eval:
  dataset:
    type: DetDataset                                                  # File reading method. Here we use the `Common Dataset` format
    dataset_root: dir/to/data/                                        # Root directory of the data
    data_dir: validation/                                             # Validation dataset directory. It will be concatenated with `dataset_root` to form a complete path.
    label_file: val_det.txt                                     # Path of the validation label. It will be concatenated with `dataset_root` to form a complete path.
  ...

2.2 Configure train/validation transform pipelines

Take the train.dataset.transform_pipeline field in the configs/det/dbnet/dbnet_r50_icdar15.yaml as an example. It specifies a set of transformations applied on the image or labels to generate the data as the model inputs or the loss function inputs. These transform functions are defined in mindocr/data/transforms.

...
train:
...
  dataset:
    transform_pipeline:
      - DecodeImage:
          img_mode: RGB
          to_float32: False
      - DetLabelEncode:
      - RandomColorAdjust:
          brightness: 0.1255  # 32.0 / 255
          saturation: 0.5
      - RandomHorizontalFlip:
          p: 0.5
      - RandomRotate:
          degrees: [ -10, 10 ]
          expand_canvas: False
          p: 1.0
      - RandomScale:
          scale_range: [ 0.5, 3.0 ]
          p: 1.0
      - RandomCropWithBBox:
          max_tries: 10
          min_crop_ratio: 0.1
          crop_size: [ 640, 640 ]
          p: 1.0
      - ValidatePolygons:
      - ShrinkBinaryMap:
          min_text_size: 8
          shrink_ratio: 0.4
      - BorderMap:
          shrink_ratio: 0.4
          thresh_min: 0.3
          thresh_max: 0.7
      - NormalizeImage:
          bgr_to_rgb: False
          is_hwc: True
          mean: imagenet
          std: imagenet
      - ToCHWImage:
  ...

  • DecodeImage and DetLabelEncode: the two transform functions parse the strings in train_det.txt file, load both the image and the labels, and save them as a dictionary;

  • RandomColorAdjust, RandomHorizontalFlip, RandomRotate, RandomScale, and RandomCropWithBBox: these transform functions perform typical image augmentation operations. Except for RandomColorAdjust, all other functions alter the bounding box labels;

  • ValidatePolygons: it filters out the bounding boxes that are outside of the image due to previous augmentations;

  • ShrinkBinaryMap and BorderMap: they make the binary map and the border map needed for dbnet training;

  • NormalizeImage: it normalizes the image by the mean and variance of the ImageNet dataset;

  • ToCHWImage: it changes HWC images to CHW images.

For validation transform pipeline, all image augmentation operations are removed, and replaced by a simple resize function:

eval:
  dataset
    transform_pipeline:
      - DecodeImage:
          img_mode: RGB
          to_float32: False
      - DetLabelEncode:
      - DetResize:
          target_size: [ 736, 1280 ]
          keep_ratio: False
          force_divisable: True
      - NormalizeImage:
          bgr_to_rgb: False
          is_hwc: True
          mean: imagenet
          std: imagenet
      - ToCHWImage:

More tutorials on transform functions can be found in the transform tutorial.

2.3 Configure the model architecture

Although different models have different architectures, MindOCR formulates them as a general three-stage architecture: [backbone]->[neck]->[head]. Take configs/det/dbnet/dbnet_r50_icdar15.yaml as an example:

model:
  type: det
  transform: null
  backbone:
    name: det_resnet50  # Only ResNet50 is supported at the moment
    pretrained: True    # Whether to use weights pretrained on ImageNet
  neck:
    name: DBFPN         # FPN part of the DBNet
    out_channels: 256
    bias: False
    use_asf: False      # Adaptive Scale Fusion module from DBNet++ (use it for DBNet++ only)
  head:
    name: DBHead
    k: 50               # amplifying factor for Differentiable Binarization
    bias: False
    adaptive: True      # True for training, False for inference

The backbone, neck, and head modules are all defined under mindocr/models/backbones, mindocr/models/necks, and mindocr/models/heads.

2.4 Configure training hyperparameters

Some training hyperparameters in configs/det/dbnet/dbnet_r50_icdar15.yaml are defined as follows:

metric:
  name: DetMetric
  main_indicator: f-score

loss:
  name: DBLoss
  eps: 1.0e-6
  l1_scale: 10
  bce_scale: 5
  bce_replace: bceloss

scheduler:
  scheduler: polynomial_decay
  lr: 0.007
  num_epochs: 1200
  decay_rate: 0.9
  warmup_epochs: 3

optimizer:
  opt: SGD
  filter_bias_and_bn: false
  momentum: 0.9
  weight_decay: 1.0e-4

It uses SGD optimizer (in mindocr/optim/optim.factory.py) and polynomial_decay (in mindocr/scheduler/scheduler_factory.py) as the learning scheduler. The loss function is DBLoss (in mindocr/losses/det_loss.py) and the evaluation metric is DetMetric ( in mindocr/metrics/det_metrics.py).

3. Model Training, Evaluation, and Inference

When all configurations have been specified, users can start training their models. MindOCR supports evaluation and inference after the model is trained.

3.1 Training

  • Standalone training

In standalone training, the model is trained on a single device (device:0 by default). Users should set system.distribute in yaml config file to be False, and the system.device_id to the target device id if users want to run this model on a device other than device:0.

Take configs/det/dbnet/db_r50_icdar15.yaml as an example, the training command is:

python tools/train.py -c=configs/det/dbnet/db_r50_icdar15.yaml
  • Distributed training

In distributed training, distribute in yaml config file should be True. On Ascend devices, users can use mpirun to launch distributed training. For example, using device:0 and device:1 to train:

# n is the number of NPUs
mpirun --allow-run-as-root -n 2 python tools/train.py --config configs/det/dbnet/db_r50_icdar15.yaml

Sometimes, users may want to specify the device ids to run distributed training, for example, device:2 and device:3.

On Ascend devices, users should create a rank_table.json like this:

Copy{
    "version": "1.0",
    "server_count": "1",
    "server_list": [
        {
            "server_id": "10.155.111.140",
            "device": [
                {"device_id": "2","device_ip": "192.3.27.6","rank_id": "2"},
                {"device_id": "3","device_ip": "192.4.27.6","rank_id": "3"}],
             "host_nic_ip": "reserve"
        }
    ],
    "status": "completed"
}

To get the device_ip of the target device, run cat /etc/hccn.conf and look for the value of address_x, which is the ip address. More details can be found in distributed training tutorial.

3.2 Evaluation

To evaluate the accuracy of the trained model, users can use tools/eval.py.

Take standalone evaluation as an example. In the yaml config file, system.distribute should be False; the eval.ckpt_load_path should be the target ckpt path; eval.dataset_root, eval.data_dir, and eval.label_file should be correctly specified. Then the evaluation can be started by running:

python tools/eval.py -c=configs/det/dbnet/db_r50_icdar15.yaml

MindOCR also supports to specify the arguments in the command line, by running:

python tools/eval.py -c=configs/det/dbnet/db_r50_icdar15.yaml \
            --opt eval.ckpt_load_path="/path/to/local_ckpt.ckpt" \
                  eval.dataset_root="/path/to/val_set/root" \
                  eval.data_dir="val_set/dir"\
                  eval.label_file="val_set/label"

3.3 Inference

MindOCR inference supports Ascend310/Ascend310P devices and adopts MindSpore Lite inference backend. Inference Tutorial gives detailed steps on how to run inference with MindOCR, which include mainly three steps: environment preparation, model conversion, and inference.

3.3.1 Environment Preparation

Please refer to the environment installation for more information.

3.3.2 Model Conversion

Before runing infernence, users need to export a MindIR file from the trained checkpoint. MindSpore IR (MindIR) is a function-style IR based on graph representation. The MindIR filew stores the model structure and weight parameters needed for inference.

Given the trained dbnet checkpoint file, user can use the following commands to export MindIR:

python tools/export.py --model_name_or_config dbnet_resnet50 --data_shape 736 1280 --local_ckpt_path /path/to/local_ckpt.ckpt
# or
python tools/export.py --model_name_or_config configs/det/dbnet/db_r50_icdar15.yaml --data_shape 736 1280 --local_ckpt_path /path/to/local_ckpt.ckpt

The data_shape is the model input shape of height and width for MindIR file. It may change when the model is changed.

Please refer to the Conversion Tutorial for more details about model conversion.

3.3.3 Inference

After model conversion, the output.mindir is obtained. Users can go to the deploy/py_infer directory, and use the following command for inference:

python infer.py \
    --input_images_dir=/your_path_to/test_images \
    --device=Ascend \
    --device_id=0 \
    --det_model_path=your_path_to/output.mindir \
    --det_model_name_or_config=../../configs/det/dbnet/db_r50_icdar15.yaml \
    --backend=lite \
    --res_save_dir=results_dir

Please refer to the Inference Tutorials chapter 4.1 Command example on more examples of inference commands.