jpylyzer

About

Jpylyzer is a JP2 (JPEG 2000 Part 1) image validator and properties extractor. Its development was partially supported by the SCAPE Project. The SCAPE project is co-funded by the European Union under FP7 ICT-2009.4.1 (Grant Agreement number 270137).

Jpylyzer homepage

Please visit the jpylyzer homepage for links to the most recent package downloads (Debian packages and Windows binaries), and a User Manual which documents all aspects of the software:

https://jpylyzer.openpreservation.org/

CI Status

• Travis-CI

• OPF Jenkins

Using jpylyzer from the command line

Calling jpylyzer in a command window without any arguments results in the following helper message:

usage: jpylyzer [-h] [--format FMT] [--mix {1,2}] [--nopretty]
            [--nullxml] [--recurse] [--packetmarkers] [--verbose]
            [--version] jp2In [jp2In ...]

Positional arguments

Optional arguments

Output

Output is directed to the standard output device (stdout).

Examples

Validate JP2 image:

jpylyzer rubbish.jp2 > rubbish-jp2.xml`

Validate JPEG 2000 Part 1 codestream:

jpylyzer --format j2c rubbish.j2c > rubbish-j2c.xml`

Validate JPH (High Throughput) image:

jpylyzer --format jph rubbish.jph > rubbish-jph.xml`

Validate JPEG 2000 Part 15 (High Throughput) codestream:

jpylyzer --format jhc rubbish.jhc > rubbish-jhc.xml`

In the above examples, output is redirected to the output files ‘rubbish-???.xml’. By default jpylyzer’s XML is pretty-printed, so you should be able to view the file using your favourite text editor. Alternatively use a dedicated XML editor, or open the file in your web browser.

Output format

The output file contains the following top-level elements:

1. One toolInfo element, which contains information about jpylyzer (its name and version number)

2. One or more file elements, each of which contain information about about the analysed files

In turn, each file element contains the following sub-elements:

1. fileInfo: general information about the analysed file

2. statusInfo: information about the status of jpylyzer's validation attempt

3. isValid: outcome of the validation

4. tests: outcome of the individual tests that are part of the validation process (organised by box)

5. properties: image properties (organised by box)

6. propertiesExtension: wrapper element for NISO MIX output (only if the --mix option is used)

7. warnings: reported warnings

Using jpylyzer as a Python module

Instead of using jpylyzer from the command-line, you can also import it as a module in your own Python programs. To do so, install jpylyzer with pip in a virtual environment:

pip install jpylyzer

Then import jpylyzer into your code by adding:

from jpylyzer import jpylyzer

Subsequently you can call any function that is defined in jpylyzer.py. In practice you will most likely only need the checkOneFile function. The following minimal script shows how this works:

#! /usr/bin/env python3

from jpylyzer import jpylyzer

# Define JP2
myFile = "/home/johan/jpylyzer-test-files/aware.jp2"

# Analyse with jpylyzer, result to Element object
myResult = jpylyzer.checkOneFile(myFile)

# Return image height value
imageHeight = myResult.findtext('./properties/jp2HeaderBox/imageHeaderBox/height')
print(imageHeight)

Here, myResult is an Element object that can either be used directly, or converted to XML using the ElementTree module[^3].

For validation a raw JPEG 2000 codestreams, call the checkOneFile function with the additional validationFormat argument, and set it to j2c:

# Define Codestream
myFile = "/home/johan/jpylyzer-test-files/rubbish.j2c"

# Analyse with jpylyzer, result to Element object
myResult = jpylyzer.checkOneFile(myFile, 'j2c')

Validator modules and classes

As of Jpylyzer 2.3, the validator functions are spread across 6 modules, each of which contains a validator class. These validator classes are all child classes of the "Validator" base class that is defined in validator.py:

• jp2.py - Top-level JP2 / JPH validation (class JP2Validator)
• boxes.py - Validation of all defined boxes for JP2 and JPH (class BoxValidator)
• codestream.py - JPEG 2000 codestream validation (class CSValidator)
• tilepart.py - Validation of one tile part of a JPEG 2000 codestream (class TilePartValidator)
• csmarkers.py - Validation of JPEG 2000 codestream marker segments (class CSMarkerValidator)
• icc.py - Feature extraction from an ICC profile (class IccValidator)

The table below shows how each higher-level classe imports all classes that are needed for validation at the underlying level:

Steps in preparing a jpylyzer release

See instructions here