ocrd_imageconvert

Thin wrapper around convert(1)

Introduction

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.

Installation

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).

Usage

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.

Example

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.)

Testing

None yet