Thin wrapper around convert(1)
ImageMagick's convert CLI contains a treasure trove of image operations. This wrapper aims to provide much of that as an OCR-D compliant processor.
This module requires GNU make (for installation) and the ImageMagick command line tools (at runtime). On Ubuntu 18.04 (or similar), you can install them by running:
sudo apt-get install make
sudo make deps-ubuntu # or: apt-get install imagemagick
Moreover, an installation of OCR-D core is needed:
make deps # or: pip install ocrd
This will install the Python package ocrd in your current environment. (Setting up a venv is strongly recommended.)
Lastly, the provided shell script ocrd-im6convert works best when copied into your PATH, referencing its ocrd-tool.json under a known path. This can be done by running:
make install
This will copy the binary and JSON file under $PREFIX, which variable you can override to your needs. The default value is to use PREFIX=$VIRTUAL_ENV if you have already activated a venv, or PREFIX=$PWD/.local (i.e. under the current working directory).
This package provides ocrd-im6convert as a OCR-D processor (command line interface). It uses the following parameters:
"ocrd-im6convert": {
"executable": "ocrd-im6convert",
"categories": ["Image preprocessing"],
"steps": ["preprocessing/optimization"],
"description": "Convert and transform images",
"input_file_grp": [
"OCR-D-IMG"
],
"output_file_grp": [
"OCR-D-IMG"
],
"parameters": {
"input-options": {
"type": "string",
"description": "e.g. -density 600x600 -wavelet-denoise 1%x0.1",
"default": ""
},
"output-format": {
"type": "string",
"description": "Desired media type of output",
"required": true,
"enum": ["image/tiff", "image/jp2", "image/png"]
},
"output-options": {
"type": "string",
"description": "e.g. -resample 300x300 -alpha deactivate -normalize -despeckle -noise 2 -negate -morphology close diamond",
"default": ""
}
}
}Cf. IM documentation or man-page convert(1) for formats and options.
ocrd-im6convert -I OCR-D-IMG -O OCR-D-IMG-SMALL -p '{ "output-format": "image/png", "output-options": "-resize 24%" }'
(This downscales the images in the input file group OCR-D-IMG to 24% and stores them as PNG files under the output file group OCR-D-IMG-SMALL.)
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