Training workflow for Tesseract 4 as a Makefile for dependency tracking and building the required software from source.
You will need at least GNU make (minimal version 4.2), wget, find, bash, unzip and bc.
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.
- Install the latest tesseract (e.g. from https://digi.bib.uni-mannheim.de/tesseract/) make sure that tesseract is add to your PATH.
- Install Python 3
- Install Git SCM to Windows - it provides a lot of linux utilities on Windows (e.g.
find,unzip,rm) and putC:\Program Files\Git\usr\binto the begining of your PATH variable (temporarely you can do it incmdwithset PATH=C:\Program Files\Git\usr\bin;%PATH%- unfornatelly there are several Windows tools with the same name as on linux (find,sort) with different behaviour/functionality and there is need to avoid them during training. - Install winget/Windows Package Manager and then run
winget install GnuWin32.Makeandwinget install wgetto install missing tools. - Download Bc and dc calculator in Windows and unzip bc.exe somewhere to your path (e.g. in my case
unzip -j bc-1.07.1-win32-embedeo-02.zip "bc-1.07.1-win32-embedeo-02/bin/bc.exe" -d "c:\Program Files\Tools")
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.
Tesseract expects some configuration data (a file radical-stroke.txt and *.unicharset for all scripts) in DATA_DIR.
To fetch them:
make tesseract-langdata
(This step is only needed once and already included implicitly in the training target,
but you might want to run explicitly it in advance.)
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.
Run
make training MODEL_NAME=name-of-the-resulting-model
which is basically a shortcut for
make unicharset lists proto-model tesseract-langdata training
Run make help to see all the possible targets and variables:
Targets
unicharset Create unicharset
charfreq Show character histogram
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 minimal stock models
tesseract-langdata Download stock unicharsets
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 in plot subdirectory for plotting of different training scenarios. The training
log is expected to be saved in plot/TESSTRAIN.LOG.
As an example, use the training data provided in ocrd-testset.zip to do training and generate the plots. Plotting can be done while training is running also to depict the training status till then.
unzip ocrd-testset.zip -d data/ocrd-ground-truth
nohup make training MODEL_NAME=ocrd START_MODEL=frk TESSDATA=~/tessdata_best MAX_ITERATIONS=10000 > plot/TESSTRAIN.LOG &
cd ./plot
./plot_cer.sh
tesstrain provides a utility tesstrain-extract-sets to generate pairs of text lines and corresponding line images from input data in the form of
ALTO or
PAGE-XML files that represent scanned pages (complete or partial) with existing OCR.
To install tesstrain-extract-sets, first set up a virtual environment and install the project via pip:
# create virtual environment in subfolder "venv"
python3 -m venv venv
# unix
source venv/bin/activate
# win
venv\Scripts\activate.bat
# actual install
pip install .
tesstrain-extract-sets currently supports OCR data in ALTO V3, PAGE 2013 and PAGE 2019, as well as TIFF, JPEG and PNG images.
Output is written as UTF-8 encoded plain text files and TIFF images. The image frame is produced from the textline coordinates in the OCR data, so please take care of properly annotated geometrical information. Additionally, the tool can add a fixed synthetic padding around the textline or store it binarized (--binarize).
By default, several sanitize actions are performed at image line level, like deskewing or removement of top-bottom intruders. To disable this, add flag --no-sanitze.
See tesstrain-extract-sets --help for a brief listing of all supported command line flags and options.
NOTE: The text of the lines is extracted as-is, no automatic correction takes place. It is strongly recommended to review the generated data before training Tesseract with it.
Software is provided under the terms of the Apache 2.0 license.
Sample training data provided by Deutsches Textarchiv is in the public domain.