OCR-D wrapper for arbitrary coords-preserving image operations
This offers OCR-D compliant workspace processors for any image processing tools which have some (usable) CLI and do not modify/invalidate image coordinates.
It thus wraps them for OCR-D without the need to write and manage code for each of them individually (exposing/passing/documenting their parameters and usage, managing releases etc). It shifts all the burden to workflow configuration (i.e. defining a suitable parameter set on how to call what program on what data, and installing all the required tools).
It is itself written in Python, and relies heavily on the OCR-D core API. This is responsible for handling METS/PAGE, and providing the OCR-D CLI.
In addition, this aims to wrap existing Python packages for preprocessing as OCR-D processors (one at a time).
Create and activate a virtual environment as usual.
To install Python dependencies:
make deps
Which is the equivalent of:
pip install -r requirements.txt
To install this module, then do:
make install
Which is the equivalent of:
pip install .
ocrd-preprocess-imageTo be used with PAGE-XML documents in an OCR-D annotation workflow.
Usage: ocrd-preprocess-image [OPTIONS]
Convert or enhance images
> Performs coords-preserving image operations via runtime shell calls
> anywhere.
> Open and deserialize PAGE input files and their respective images,
> then iterate over the element hierarchy down to the requested
> ``level-of-operation`` in the element hierarchy.
> For each segment element, retrieve a segment image according to the
> layout annotation (from an existing AlternativeImage, or by cropping
> via coordinates into the higher-level image, and - when applicable -
> deskewing.
> If ``input_feature_selector`` and/or ``input_feature_filter`` is
> non-empty, then select/filter among the @imageFilename image and the
> available AlternativeImages the last one which contains all of the
> selected, but none of the filtered features (i.e. @comments
> classes), or raise an error.
> Then write that image into a temporary PNG file, create a new METS
> file ID for the result image (based on the segment ID and the
> operation to be run), along with a local path for it, and pass
> ``command`` to the shell after replacing: - the string ``@INFILE``
> with that input image path, and - the string ``@OUTFILE`` with that
> output image path.
> If the shell returns with a failure, skip that segment with an
> approriate error message. Otherwise, add the new image to the
> workspace along with the output fileGrp, and using a file ID with
> suffix ``.IMG-``, and further identification of the input element.
> Reference it as AlternativeImage in the element, adding
> ``output_feature_added`` to its @comments.
> Produce a new PAGE output file by serialising the resulting
> hierarchy.
Options:
-I, --input-file-grp USE File group(s) used as input
-O, --output-file-grp USE File group(s) used as output
-g, --page-id ID Physical page ID(s) to process
--overwrite Remove existing output pages/images
(with --page-id, remove only those)
-p, --parameter JSON-PATH Parameters, either verbatim JSON string
or JSON file path
-P, --param-override KEY VAL Override a single JSON object key-value pair,
taking precedence over --parameter
-m, --mets URL-PATH URL or file path of METS to process
-w, --working-dir PATH Working directory of local workspace
-l, --log-level [OFF|ERROR|WARN|INFO|DEBUG|TRACE]
Log level
-J, --dump-json Dump tool description as JSON and exit
-h, --help This help message
-V, --version Show version
Parameters:
"level-of-operation" [string - "page"]
PAGE XML hierarchy level to operate on
Possible values: ["page", "region", "line", "word", "glyph"]
"input_feature_selector" [string - ""]
comma-separated list of required image features (e.g.
binarized,despeckled)
"input_feature_filter" [string - ""]
comma-separated list of forbidden image features (e.g.
binarized,despeckled)
"output_feature_added" [string - REQUIRED]
image feature(s) to be added after this operation (if multiple,
separate by comma)
"input_mimetype" [string - "image/png"]
File format to save input images to (tool's expected input)
Possible values: ["image/bmp", "application/postscript", "image/gif",
"image/jpeg", "image/jp2", "image/png", "image/x-portable-pixmap",
"image/tiff"]
"output_mimetype" [string - "image/png"]
File format to load output images from (tool's expected output)
Possible values: ["image/bmp", "application/postscript", "image/gif",
"image/jpeg", "image/jp2", "image/png", "image/x-portable-pixmap",
"image/tiff"]
"command" [string - REQUIRED]
shell command to operate on image files, with @INFILE as place-holder
for the input file path, and @OUTFILE as place-holder for the output
file path
The following example recipes are included in the distribution:
ocrd-skimage-normalizeTo be used with PAGE-XML documents in an OCR-D annotation workflow.
Usage: ocrd-skimage-normalize [OPTIONS]
Equalize contrast/exposure of images with Scikit-image; stretches the color value/tone to the full dynamic range
> Performs contrast-enhancing equalization of segment or page images
> with scikit-image on the workspace.
> Open and deserialize PAGE input files and their respective images,
> then iterate over the element hierarchy down to the requested
> ``level-of-operation`` in the element hierarchy.
> For each segment element, retrieve a segment image according to the
> layout annotation (from an existing AlternativeImage, or by cropping
> via coordinates into the higher-level image, and - when applicable -
> deskewing), in raw (non-binarized) form.
> Next, normalize the image according to ``method`` in skimage.
> Then write the new image to the workspace along with the output
> fileGrp, and using a file ID with suffix ``.IMG-NRM`` with further
> identification of the input element.
> Produce a new PAGE output file by serialising the resulting
> hierarchy.
Options:
-I, --input-file-grp USE File group(s) used as input
-O, --output-file-grp USE File group(s) used as output
-g, --page-id ID Physical page ID(s) to process
--overwrite Remove existing output pages/images
(with --page-id, remove only those)
-p, --parameter JSON-PATH Parameters, either verbatim JSON string
or JSON file path
-P, --param-override KEY VAL Override a single JSON object key-value pair,
taking precedence over --parameter
-m, --mets URL-PATH URL or file path of METS to process
-w, --working-dir PATH Working directory of local workspace
-l, --log-level [OFF|ERROR|WARN|INFO|DEBUG|TRACE]
Log level
-J, --dump-json Dump tool description as JSON and exit
-h, --help This help message
-V, --version Show version
Parameters:
"level-of-operation" [string - "page"]
PAGE XML hierarchy level to operate on
Possible values: ["page", "region", "line", "word", "glyph"]
"dpi" [number - 0]
pixel density in dots per inch (overrides any meta-data in the
images); disabled when zero
"black-point" [number - 1.0]
black point point in percent of luminance/value/tone histogram; up to
``black-point`` darkest pixels will be clipped to black when
stretching
"white-point" [number - 7.0]
white point in percent of luminance/value/tone histogram; up to
``white-point`` brightest pixels will be clipped to white when
stretching
"method" [string - "stretch"]
contrast-enhancing transformation to use after clipping; ``stretch``
uses ``skimage.exposure.rescale_intensity`` (globally linearly
stretching to full dynamic range) and ``adapthist`` uses
``skimage.exposure.equalize_adapthist`` (applying over tiles with
context from 1/8th of the image's width)
Possible values: ["stretch", "adapthist"]
ocrd-skimage-denoise-rawTo be used with PAGE-XML documents in an OCR-D annotation workflow.
Usage: ocrd-skimage-denoise-raw [OPTIONS]
Denoise raw images with Scikit-image
> Performs raw denoising of segment or page images with scikit-image
> on the workspace.
> Open and deserialize PAGE input files and their respective images,
> then iterate over the element hierarchy down to the requested
> ``level-of-operation`` in the element hierarchy.
> For each segment element, retrieve a segment image according to the
> layout annotation (from an existing AlternativeImage, or by cropping
> via coordinates into the higher-level image, and - when applicable -
> deskewing), in raw (non-binarized) form.
> Next, denoise the image with a Wavelet transform scheme according to
> ``method`` in skimage.
> Then write the new image to the workspace along with the output
> fileGrp, and using a file ID with suffix ``.IMG-DEN`` with further
> identification of the input element.
> Produce a new PAGE output file by serialising the resulting
> hierarchy.
Options:
-I, --input-file-grp USE File group(s) used as input
-O, --output-file-grp USE File group(s) used as output
-g, --page-id ID Physical page ID(s) to process
--overwrite Remove existing output pages/images
(with --page-id, remove only those)
-p, --parameter JSON-PATH Parameters, either verbatim JSON string
or JSON file path
-P, --param-override KEY VAL Override a single JSON object key-value pair,
taking precedence over --parameter
-m, --mets URL-PATH URL or file path of METS to process
-w, --working-dir PATH Working directory of local workspace
-l, --log-level [OFF|ERROR|WARN|INFO|DEBUG|TRACE]
Log level
-J, --dump-json Dump tool description as JSON and exit
-h, --help This help message
-V, --version Show version
Parameters:
"level-of-operation" [string - "page"]
PAGE XML hierarchy level to operate on
Possible values: ["page", "region", "line", "word", "glyph"]
"dpi" [number - 0]
pixel density in dots per inch (overrides any meta-data in the
images); disabled when zero
"method" [string - "VisuShrink"]
Wavelet filtering scheme to use
Possible values: ["BayesShrink", "VisuShrink"]
ocrd-skimage-binarizeTo be used with PAGE-XML documents in an OCR-D annotation workflow.
Usage: ocrd-skimage-binarize [OPTIONS]
Binarize images with Scikit-image
> Performs binarization of segment or page images with scikit-image on
> the workspace.
> Open and deserialize PAGE input files and their respective images,
> then iterate over the element hierarchy down to the requested
> ``level-of-operation`` in the element hierarchy.
> For each segment element, retrieve a segment image according to the
> layout annotation (from an existing AlternativeImage, or by cropping
> via coordinates into the higher-level image, and - when applicable -
> deskewing).
> Next, binarize the image according to ``method`` with skimage.
> Then write the new image to the workspace along with the output
> fileGrp, and using a file ID with suffix ``.IMG-BIN`` with further
> identification of the input element.
> Produce a new PAGE output file by serialising the resulting
> hierarchy.
Options:
-I, --input-file-grp USE File group(s) used as input
-O, --output-file-grp USE File group(s) used as output
-g, --page-id ID Physical page ID(s) to process
--overwrite Remove existing output pages/images
(with --page-id, remove only those)
-p, --parameter JSON-PATH Parameters, either verbatim JSON string
or JSON file path
-P, --param-override KEY VAL Override a single JSON object key-value pair,
taking precedence over --parameter
-m, --mets URL-PATH URL or file path of METS to process
-w, --working-dir PATH Working directory of local workspace
-l, --log-level [OFF|ERROR|WARN|INFO|DEBUG|TRACE]
Log level
-J, --dump-json Dump tool description as JSON and exit
-h, --help This help message
-V, --version Show version
Parameters:
"level-of-operation" [string - "page"]
PAGE XML hierarchy level to operate on
Possible values: ["page", "region", "line", "word", "glyph"]
"dpi" [number - 0]
pixel density in dots per inch (overrides any meta-data in the
images); disabled when zero
"method" [string - "sauvola"]
Thresholding algorithm to use
Possible values: ["sauvola", "niblack", "otsu", "gauss", "yen", "li"]
"window_size" [number - 0]
For Sauvola/Niblack/Gauss, the (odd) window size in pixels; when zero
(default), set to DPI
"k" [number - 0.34]
For Sauvola/Niblack, formula parameter influencing the threshold
bias; larger is lighter foreground
ocrd-skimage-denoiseTo be used with PAGE-XML documents in an OCR-D annotation workflow.
Usage: ocrd-skimage-denoise [OPTIONS]
Denoise binarized images with Scikit-image
> Performs binary denoising of segment or page images with scikit-
> image on the workspace.
> Open and deserialize PAGE input files and their respective images,
> then iterate over the element hierarchy down to the requested
> ``level-of-operation`` in the element hierarchy.
> For each segment element, retrieve a segment image according to the
> layout annotation (from an existing AlternativeImage, or by cropping
> via coordinates into the higher-level image, and - when applicable -
> deskewing), in binarized form.
> Next, denoise the image by removing too small connected components
> with skimage.
> Then write the new image to the workspace along with the output
> fileGrp, and using a file ID with suffix ``.IMG-DEN`` with further
> identification of the input element.
> Produce a new PAGE output file by serialising the resulting
> hierarchy.
Options:
-I, --input-file-grp USE File group(s) used as input
-O, --output-file-grp USE File group(s) used as output
-g, --page-id ID Physical page ID(s) to process
--overwrite Remove existing output pages/images
(with --page-id, remove only those)
-p, --parameter JSON-PATH Parameters, either verbatim JSON string
or JSON file path
-P, --param-override KEY VAL Override a single JSON object key-value pair,
taking precedence over --parameter
-m, --mets URL-PATH URL or file path of METS to process
-w, --working-dir PATH Working directory of local workspace
-l, --log-level [OFF|ERROR|WARN|INFO|DEBUG|TRACE]
Log level
-J, --dump-json Dump tool description as JSON and exit
-h, --help This help message
-V, --version Show version
Parameters:
"level-of-operation" [string - "page"]
PAGE XML hierarchy level to operate on
Possible values: ["page", "region", "line", "word", "glyph"]
"dpi" [number - 0]
pixel density in dots per inch (overrides any meta-data in the
images); disabled when zero
"maxsize" [number - 3]
maximum component size of (bg holes or fg specks) noise in pt
none yet
FAQs
OCR-D wrapper for arbitrary coords-preserving image operations
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