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RobustScanner

RobustScanner: Dynamically Enhancing Positional Clues for Robust Text Recognition

1. Introduction

RobustScanner is an encoder-decoder text recognition algorithm with attention mechanism. The authors of this paper conducted research on the mainstream encoder-decoder recognition frameworks and found that during the decoding process, text not only relies on contextual information but also utilizes positional information. However, most methods rely too much on context information during the decoding process, leading to serious attention shifting problems and thus result in poor performance for text recognition with weak context information or contextless information.

To address this issue, the authors proposed a novel position-enhancement branch and dynamically fused its output with the output of the decoder attention module. The position-enhancement branch includes a position-aware module, a position embedding layer, and an attention module. The position-aware module enhances the output feature map of the encoder to encode rich position information. The position embedding layer takes the current decoding step as input and encodes it into a vector.

Overall, the RobustScanner model consists of an encoder and a decoder. The encoder uses ResNet-31 to extract features from the image. The decoder includes a hybrid branch and a position-enhancement branch, and the outputs of the two branches are dynamically fused and used to predict the final result. Based on the special design for position information, RobustScanner achieved the state-of-the-art results on both regular and irregular text recognition benchmarks and showed robustness in both contextual and non-contextual application scenarios.

Figure 1. Overall RobustScanner architecture [1]

2. Results

Accuracy

According to our experiments, the evaluation results on public benchmark datasets (IC03, IC13, IC15, IIIT, SVT, SVTP, CUTE) is as follow:

Model	Context	Backbone	Avg Accuracy	Train T.	FPS	ms/step	Recipe	Download
RobustScanner	D910x4-MS2.0-G	ResNet-31	87.86%	22560 s/epoch	310	825	yaml	ckpt \| mindir

Note: In addition to using the MJSynth (partial) and SynthText (partial) text recognition datasets, RobustScanner is also trained with the SynthAdd dataset and some real datasets. The specific details of the data can be found in the paper or here.

Detailed accuracy results for each benchmark dataset

Model	Backbone	IIIT5k	SVT	IC13	IC15	SVTP	CUTE80	Average
RobustScanner	ResNet-31	95.50%	92.12%	94.29%	73.33%	82.33%	89.58%	87.86%

Notes:

Context: Training context denoted as {device}x{pieces}-{MS mode}, where mindspore mode can be G-graph mode or F-pynative mode with ms function. For example, D910x4-MS1.10-G is for training on 4 pieces of Ascend 910 NPU using graph mode based on Minspore version 1.10.
To reproduce the result on other contexts, please ensure the global batch size is the same.
The model uses an English character dictionary, en_dict90.txt, consisting of 90 characters including digits, common symbols, and upper and lower case English letters. More explanation on dictionary, please refer to 4. Character Dictionary.
The models are trained from scratch without any pre-training. For more dataset details of training and evaluation, please refer to Dataset Download & Dataset Usage section.
The input Shapes of MindIR of RobustScanner is (1, 3, 48, 160) and it is for Ascend only.

3. Quick Start

3.1 Preparation

3.1.1 Installation

Please refer to the installation instruction in MindOCR.

3.1.2 Dataset Download

The dataset used for training and validation in this work, was referenced from the datasets used by mmocr and PaddleOCR for reproducing the RobustScanner algorithms. We are very grateful to mmocr and PaddleOCR for improving the reproducibility efficiency of this repository.

The details of the dataset are as follows:

Training set	instance num	repeat num	type
icdar2013	848	20	real
icdar2015	4468	20	real
coco_text	42142	20	real
IIIT5K	2000	20	real
SynthText	2400000	1	synth
SynthAdd	1216889	1	synth
Syn90k	2400000	1	synth

Note: SynthText and Syn90k datasets were both randomly sampled the complete SynthText dataset and complete Syn90k dataset, consisting of 2.4 million samples each.

The training and evaluation datasets in LMDB format shown in the table above can be downloaded from here: training set, evaluation set

The downloaded file contains several compressed files, including:

Training set
- training_lmdb_real.zip: contains four real datasets,IIIT5K, icdar2013, icdar2015 and coco_text, which are repeated 20 times during training;
- SynthAdd.zip: contains the complete SynthAdd dataset;
- synth90K_shuffle.zip: contains 2.4 million randomly sampled samples from the Synth90k dataset;
- SynthText800K_shuffle_xxx_xxx.zip: includes 5 zip files, 1_200, and a total of 2.4 million randomly sampled samples from the SynthText dataset.
Evaluation set
- testing_lmdb.zip: contains six datasets used for evaluating the model, including CUTE80, icdar2013, icdar2015, IIIT5k, SVT, and SVTP.

3.1.3 Dataset Usage

The data folder should be unzipped following the directory structure below:

data/
├── training
│   ├── real_data
│   │   ├── repeat1
│   │   │   ├── COCO_Text
│   │   │   │   ├── data.mdb
│   │   │   │   └── lock.mdb
│   │   │   ├── ICDAR2013
│   │   │   │   ├── data.mdb
│   │   │   │   └── lock.mdb
│   │   │   ├── ICDAR2015
│   │   │   │   ├── data.mdb
│   │   │   │   └── lock.mdb
│   │   │   └── IIIT5K
│   │   │       ├── data.mdb
│   │   │       └── lock.mdb
│   │   ├── repeat2
│   │   │   ├── COCO_Text
│   │   │   ├── ICDAR2013
│   │   │   ├── ICDAR2015
│   │   │   └── IIIT5K
│   │   │
│   │   ├── ...
│   │   │
│   │   └── repeat20
│   │       ├── COCO_Text
│   │       ├── ICDAR2013
│   │       ├── ICDAR2015
│   │       └── IIIT5K
│   └── synth_data
│       ├── synth90K_shuffle
│       │   ├── data.mdb
│       │   └── lock.mdb
│       ├── SynthAdd
│       │   ├── data.mdb
│       │   └── lock.mdb
│       ├── SynthText800K_shuffle_1_40
│       │   ├── data.mdb
│       │   └── lock.mdb
│       ├── SynthText800K_shuffle_41_80
│       │   ├── data.mdb
│       │   └── lock.mdb
│       └── ...
└── evaluation
    ├── CUTE80
    │   ├── data.mdb
    │   └── lock.mdb
    ├── IC13_1015
    │   ├── data.mdb
    │   └── lock.mdb
    ├── IC15_2077
    │   ├── data.mdb
    │   └── lock.mdb
    ├── IIIT5k_3000
    │   ├── data.mdb
    │   └── lock.mdb
    ├── SVT
    │   ├── data.mdb
    │   └── lock.mdb
    └── SVTP
        ├── data.mdb
        └── lock.mdb

Here, we use the datasets under the training/ folder for training and the datasets under the evaluation/ folder for model evaluation. For convenience of storage and usage, all data is in the lmdb format.

Data configuration for model training

To reproduce the training of model, it is recommended that you modify the configuration yaml as follows:

...
train:
  ...
  dataset:
    type: LMDBDataset
    dataset_root: path/to/data/                           # Root dir of training dataset
    data_dir: training/                                   # Dir of training dataset, concatenated with `dataset_root` to be the complete dir of training dataset
...
eval:
  dataset:
    type: LMDBDataset
    dataset_root: path/to/data/                           # Root dir of validation dataset
    data_dir: evaluation/                                 # Dir of validation dataset, concatenated with `dataset_root` to be the complete dir of validation dataset
  ...

Data configuration for model evaluation

We use the dataset under evaluation/ as the benchmark dataset. On each individual dataset (e.g. CUTE80, IC13_1015, etc.), we perform a full evaluation by setting the dataset's directory to the evaluation dataset. This way, we get a list of the corresponding accuracies for each dataset, and then the reported accuracies are the average of these values.

To reproduce the reported evaluation results, you can:

Option 1: Repeat the evaluation step for all individual datasets: CUTE80, IC13_1015, IC15_2077, IIIT5k_3000, SVT, and SVTP. Then take the average score.
Option 2: Put all the benchmark datasets folder under the same directory, e.g. evaluation/. And use the script tools/benchmarking/multi_dataset_eval.py.

Evaluate on one specific dataset

For example, you can evaluate the model on dataset CUTE80 by modifying the config yaml as follows:

...
train:
  # NO NEED TO CHANGE ANYTHING IN TRAIN SINCE IT IS NOT USED
...
eval:
  dataset:
    type: LMDBDataset
    dataset_root: path/to/data/                           # Root dir of evaluation dataset
    data_dir: evaluation/CUTE80/                          # Dir of evaluation dataset, concatenated with `dataset_root` to be the complete dir of evaluation dataset
  ...

By running tools/eval.py as noted in section Model Evaluation with the above config yaml, you can get the accuracy performance on dataset CUTE80.

Evaluate on multiple datasets under the same folder

Assume you have put all benckmark datasets under evaluation/ as shown below:

data/
├── evaluation
│   ├── CUTE80
│   │   ├── data.mdb
│   │   └── lock.mdb
│   ├── IC03_860
│   │   ├── data.mdb
│   │   └── lock.mdb
│   ├── IC03_867
│   │   ├── data.mdb
│   │   └── lock.mdb
│   ├── IC13_1015
│   │   ├── data.mdb
│   │   └── lock.mdb
│   ├── ...

then you can evaluate on each dataset by modifying the config yaml as follows, and execute the script tools/benchmarking/multi_dataset_eval.py.

...
train:
  # NO NEED TO CHANGE ANYTHING IN TRAIN SINCE IT IS NOT USED
...
eval:
  dataset:
    type: LMDBDataset
    dataset_root: path/to/data/                           # Root dir of evaluation dataset
    data_dir: evaluation/                                 # Dir of evaluation dataset, concatenated with `dataset_root` to be the complete dir of evaluation dataset
  ...

3.1.4 Check YAML Config Files

Apart from the dataset setting, please also check the following important args: system.distribute, system.val_while_train, common.batch_size, train.ckpt_save_dir, train.dataset.dataset_root, train.dataset.data_dir, eval.ckpt_load_path, eval.dataset.dataset_root, eval.dataset.data_dir, eval.loader.batch_size. Explanations of these important args:

system:
  distribute: True                                                    # `True` for distributed training, `False` for standalone training
  amp_level: 'O0'
  seed: 42
  val_while_train: True                                               # Validate while training
  drop_overflow_update: False
common:
  ...
  batch_size: &batch_size 64                                          # Batch size for training
  ...
train:
  ckpt_save_dir: './tmp_rec'                                          # The training result (including checkpoints, per-epoch performance and curves) saving directory
  dataset_sink_mode: False
  dataset:
    type: LMDBDataset
    dataset_root: path/to/data/                                       # Root dir of training dataset
    data_dir: training/                                               # Dir of training dataset, concatenated with `dataset_root` to be the complete dir of training dataset
...
eval:
  ckpt_load_path: './tmp_rec/best.ckpt'                               # checkpoint file path
  dataset_sink_mode: False
  dataset:
    type: LMDBDataset
    dataset_root: path/to/data/                                       # Root dir of validation/evaluation dataset
    data_dir: evaluation/                                             # Dir of validation/evaluation dataset, concatenated with `dataset_root` to be the complete dir of validation/evaluation dataset
  ...
  loader:
      shuffle: False
      batch_size: 64                                                  # Batch size for validation/evaluation
...

Notes:

As the global batch size (batch_size x num_devices) is important for reproducing the result, please adjust batch_size accordingly to keep the global batch size unchanged for a different number of GPUs/NPUs, or adjust the learning rate linearly to a new global batch size.

3.2 Model Training

Distributed Training

It is easy to reproduce the reported results with the pre-defined training recipe. For distributed training on multiple Ascend 910 devices, please modify the configuration parameter distribute as True and run

# distributed training on multiple GPU/Ascend devices
mpirun --allow-run-as-root -n 4 python tools/train.py --config configs/rec/robustscanner/robustscanner_resnet31.yaml

Standalone Training

If you want to train or finetune the model on a smaller dataset without distributed training, please modify the configuration parameterdistribute as False and run:

# standalone training on a CPU/GPU/Ascend device
python tools/train.py --config configs/rec/robustscanner/robustscanner_resnet31.yaml

The training result (including checkpoints, per-epoch performance and curves) will be saved in the directory parsed by the arg ckpt_save_dir. The default directory is ./tmp_rec.

3.3 Model Evaluation

To evaluate the accuracy of the trained model, you can use eval.py. Please set the checkpoint path to the arg ckpt_load_path in the eval section of yaml config file, set distribute to be False, and then run:

python tools/eval.py --config configs/rec/robustscanner/robustscanner_resnet31.yaml

4. Character Dictionary

Default Setting

To transform the groud-truth text into label ids, we have to provide the character dictionary where keys are characters and values are IDs. By default, the dictionary is "0123456789abcdefghijklmnopqrstuvwxyz", which means id=0 will correspond to the character "0". In this case, the dictionary only considers numbers and lowercase English characters, excluding spaces.

Built-in Dictionaries

There are some built-in dictionaries, which are placed in mindocr/utils/dict/, and you can choose the appropriate dictionary to use.

en_dict90.txt is an English dictionary containing 90 characters, including numbers, common symbols, and uppercase and lowercase English letters.
en_dict.txt is an English dictionary containing 94 characters, including numbers, common symbols, and uppercase and lowercase English letters.
ch_dict.txt is a Chinese dictionary containing 6623 characters, including commonly used simplified and traditional Chinese, numbers, common symbols, uppercase and lowercase English letters.

Customized Dictionary

You can also customize a dictionary file (***.txt) and place it under mindocr/utils/dict/, the format of the dictionary file should be a .txt file with one character per line.

To use a specific dictionary, change the parameter model->head->out_channels to the corresponding number, which is the number of characters in the dictionary + 3, change model->head->start_idxto the number of characters in the dictionary + 1, change model->head->padding_idxto the number of characters in the dictionary + 2, and lastly change loss->ignore_index to the number of characters in the dictionary + 2

...
model:
  type: rec
  transform: null
  backbone:
    name: rec_resnet31
    pretrained: False
  head:
    name: RobustScannerHead
    out_channels: 93                 # modify to the number of characters in the dictionary + 3
    enc_outchannles: 128
    hybrid_dec_rnn_layers: 2
    hybrid_dec_dropout: 0.
    position_dec_rnn_layers: 2
    start_idx: 91                    # modify to the number of characters in the dictionary + 1
    mask: True
    padding_idx: 92                  # modify to the number of characters in the dictionary + 2
    encode_value: False
    max_text_len: *max_text_len
...

loss:
  name: SARLoss
  ignore_index: 92                   # modify to the number of characters in the dictionary + 2

...

Notes:

You can include the space character by setting the parameter use_space_char in configuration yaml to True.
Remember to check the value of dataset->transform_pipeline->SARLabelEncode->lower in the configuration yaml. Set it to False if you prefer case-sensitive encoding.

References

[1] Xiaoyu Yue, Zhanghui Kuang, Chenhao Lin, Hongbin Sun, Wayne Zhang. RobustScanner: Dynamically Enhancing Positional Clues for Robust Text Recognition. arXiv:2007.07542, ECCV'2020

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README.md

README.md

RobustScanner

1. Introduction

2. Results

Accuracy

3. Quick Start

3.1 Preparation

3.1.1 Installation

3.1.2 Dataset Download

3.1.3 Dataset Usage

3.1.4 Check YAML Config Files

3.2 Model Training

3.3 Model Evaluation

4. Character Dictionary

Default Setting

Built-in Dictionaries

Customized Dictionary

References

Files

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README.md

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RobustScanner

1. Introduction

2. Results

Accuracy

3. Quick Start

3.1 Preparation

3.1.1 Installation

3.1.2 Dataset Download

3.1.3 Dataset Usage

3.1.4 Check YAML Config Files

3.2 Model Training

3.3 Model Evaluation

4. Character Dictionary

Default Setting

Built-in Dictionaries

Customized Dictionary

References