Training workflow for Tesseract 4 as a Makefile for dependency tracking and building the required software from source.
You will need a recent version (>= 4.0.0beta1) of tesseract built with the training tools and matching leptonica bindings. Build instructions and more can be found in the Tesseract project wiki.
Alternatively, you can build leptonica and tesseract within this project and install it to a subdirectory ./usr in the repo:
make leptonica tesseractTesseract will be built from the git repository, which requires CMake, autotools (including autotools-archive) and some additional libraries for the training tools. See the installation notes in the tesseract repository.
You need a recent version of Python 3.x. For image processing the Python library Pillow is used.
If you don't have a global installation, please use the provided requirements file pip install -r requirements.txt.
Choose a name for your model. By convention, Tesseract stack models including
language-specific resources use (lowercase) three-letter codes defined in
ISO 639 with additional
information separated by underscore. E.g., chi_tra_vert for traditional
Chinese with vertical typesetting. Language-independent (i.e. script-specific)
models use the capitalized name of the script type as identifier. E.g.,
Hangul_vert for Hangul script with vertical typesetting. In the following,
the model name is referenced by MODEL_NAME.
Place ground truth consisting of line images and transcriptions in the folder
data/MODEL_NAME-ground-truth. This list of files will be split into training and
evaluation data, the ratio is defined by the RATIO_TRAIN variable.
Images must be TIFF and have the extension .tif or PNG and have the
extension .png, .bin.png or .nrm.png.
Transcriptions must be single-line plain text and have the same name as the
line image but with the image extension replaced by .gt.txt.
The repository contains a ZIP archive with sample ground truth, see
ocrd-testset.zip. Extract it to ./data/foo-ground-truth and run
make training.
NOTE: If you want to generate line images for transcription from a full page, see tips in issue 7 and in particular @Shreeshrii's shell script.
make training MODEL_NAME=name-of-the-resulting-model
which is basically a shortcut for
make unicharset lists proto-model training
Run make help to see all the possible targets and variables:
Targets
unicharset Create unicharset
lists Create lists of lstmf filenames for training and eval
training Start training
traineddata Create best and fast .traineddata files from each .checkpoint file
proto-model Build the proto model
leptonica Build leptonica
tesseract Build tesseract
tesseract-langs Download tesseract-langs
clean Clean all generated files
Variables
MODEL_NAME Name of the model to be built. Default: foo
START_MODEL Name of the model to continue from. Default: ''
PROTO_MODEL Name of the proto model. Default: OUTPUT_DIR/MODEL_NAME.traineddata
WORDLIST_FILE Optional file for dictionary DAWG. Default: OUTPUT_DIR/MODEL_NAME.wordlist
NUMBERS_FILE Optional file for number patterns DAWG. Default: OUTPUT_DIR/MODEL_NAME.numbers
PUNC_FILE Optional file for punctuation DAWG. Default: OUTPUT_DIR/MODEL_NAME.punc
DATA_DIR Data directory for output files, proto model, start model, etc. Default: data
OUTPUT_DIR Output directory for generated files. Default: DATA_DIR/MODEL_NAME
GROUND_TRUTH_DIR Ground truth directory. Default: OUTPUT_DIR-ground-truth
CORES No of cores to use for compiling leptonica/tesseract. Default: 4
LEPTONICA_VERSION Leptonica version. Default: 1.78.0
TESSERACT_VERSION Tesseract commit. Default: 4.1.1
TESSDATA_REPO Tesseract model repo to use (_fast or _best). Default: _best
TESSDATA Path to the .traineddata directory to start finetuning from. Default: ./usr/share/tessdata
MAX_ITERATIONS Max iterations. Default: 10000
EPOCHS Set max iterations based on the number of lines for training. Default: none
DEBUG_INTERVAL Debug Interval. Default: 0
LEARNING_RATE Learning rate. Default: 0.0001 with START_MODEL, otherwise 0.002
NET_SPEC Network specification. Default: [1,36,0,1 Ct3,3,16 Mp3,3 Lfys48 Lfx96 Lrx96 Lfx256 O1c\#\#\#]
FINETUNE_TYPE Finetune Training Type - Impact, Plus, Layer or blank. Default: ''
LANG_TYPE Language Type - Indic, RTL or blank. Default: ''
PSM Page segmentation mode. Default: 13
RANDOM_SEED Random seed for shuffling of the training data. Default: 0
RATIO_TRAIN Ratio of train / eval training data. Default: 0.90
TARGET_ERROR_RATE Stop training if the character error rate (CER in percent) gets below this value. Default: 0.01
To override the default path name requirements, just set the respective variables in the above list:
make training MODEL_NAME=name-of-the-resulting-model DATA_DIR=/data GROUND_TRUTH_DIR=/data/GT
If you want to use shell variables to override the make variables (for example because
you are running tesstrain from a script or other makefile), then you can use the -e flag:
MODEL_NAME=name-of-the-resulting-model DATA_DIR=/data GROUND_TRUTH_DIR=/data/GT make -e training
When the training is finished, it will write a traineddata file which can be used
for text recognition with Tesseract. Note that this file does not include a
dictionary. The tesseract executable therefore prints an warning.
It is also possible to create additional traineddata files from intermediate
training results (the so called checkpoints). This can even be done while the
training is still running. Example:
# Add MODEL_NAME and OUTPUT_DIR like for the training.
make traineddata
This will create two directories tessdata_best and tessdata_fast in OUTPUT_DIR
with a best (double based) and fast (int based) model for each checkpoint.
It is also possible to create models for selected checkpoints only. Examples:
# Make traineddata for the checkpoint files of the last three weeks.
make traineddata CHECKPOINT_FILES="$(find data/foo -name '*.checkpoint' -mtime -21)"
# Make traineddata for the last two checkpoint files.
make traineddata CHECKPOINT_FILES="$(ls -t data/foo/checkpoints/*.checkpoint | head -2)"
# Make traineddata for all checkpoint files with CER better than 1 %.
make traineddata CHECKPOINT_FILES="$(ls data/foo/checkpoints/*[^1-9]0.*.checkpoint)"
Add MODEL_NAME and OUTPUT_DIR and replace data/foo by the output directory if needed.
Training and Evaluation CER can be plotted using matplotlib. A couple of scripts are provided as a starting point for plotting of different training scenarios.
As an example, use the training data provided in ocrd-testset.zip to do training and generate the plots.
mkdir -p data
mkdir -p data/logs
unzip ocrd-testset.zip -d data/ocrd-ground-truth
nohup make training MODEL_NAME=ocrd START_MODEL=frk TESSDATA=~/tessdata_best MAX_ITERATIONS=20000 > data/logs/TESSTRAIN.LOG &
After training is completed, you can plot the CER. Use the followingcommands:
nohup make traineddata MODEL_NAME=ocrd > data/logs/TESSDATA.LOG &
nohup make traineddata LSTMevalCER plotCER MODEL_NAME=ocrd Y_MAX_CER=4 > data/logs/TESSEVAL.LOG &
In case you get the error, Makefile:369: recipe for target 'data/ocrd/reports/ocrd-lstmeval.txt' failed, just rerun the last command once more.
Software is provided under the terms of the Apache 2.0 license.
Sample training data provided by Deutsches Textarchiv is in the public domain.