Introduction

vicar is a Python module that supports reading and writing of JPL's VICAR file format. It supports the definition of the VICAR file format as found here: https://www-mipl.jpl.nasa.gov/external/VICAR_file_fmt.pdf

Installation

The vicar module is available via the rms-vicar package on PyPI and can be installed with:

pip install rms-vicar

Getting Started

The vicar module provides these classes:

• VicarLabel: Class for reading, writing, and parsing of VICAR labels.
• VicarImage: Class for handling VICAR image (and other) data files.
• VicarError: Extension of class ValueError to contain exceptions.

Details of each class are available in the module documentation.

To read a VICAR image file:

import vicar
vic = vicar.VicarImage("path/to/file")

The resulting object contains:

• vic.array: The 3-D data array converted to native format.
• vic.array2d: Same as above, but with leading dimension (typically, bands) stripped.
• vic.prefix: The array prefix bytes as a 3-D array of unsigned bytes.
• vic.prefix2d: Same as above, but with the leading dimension stripped.
• vic.binheader: The binary header as a bytes object; use vic.binheader_array() to extract information.
• vic.label: The internal VicarLabel object that manages the VICAR label information, if direct access is needed.

VICAR parameter values can be extracted from the label using dictionary-like syntax:

• len(vic): The number of parameters in the VICAR label.
• vic['LBLSIZE']: The value of the LBLSIZE parameter (an integer).
• vic[0]: The value of the first parameter.
• vic[-1]: The value of the last parameter.
• vic['LBLSIZE',-1]: The value of the last occurrence of the LBLSIZE parameter.
• vic.get(('LBLSIZE',2), 99): The value of the third occurrence of the LBLSIZE parameter, or 99 if there are fewer than 3 occurrences.
• vic.arg('LBLSIZE'): The numeric index of "LBLSIZE" among the VICAR parameters.

You can also use dictionary-like syntax to modify and insert header values:

• vic['SOLDIST'] = 1.e9: Set SOLDICT to this value.
• del vic['SOLDIST',0]: Remove the first occurrence of SOLDIST from the label.
• vic['LBLSIZE+'] = 2000: Insert a new LBLSIZE parameter instead of modifying an existing one.

Note that certain required VICAR parameters contain structural information about the file; these cannot generally be modified directly.

Numerous methods are available to iterate over the VICAR label parameters:

for (name,value) in vic.items(): ...
for key in vic.keys(): ...
for name in vic.names(): ...
for value in vic.values(): ...

Iterators can take a regular expression as input to restrict the items returned:

for value in vic.values(r'LAB\d\d'): ...

Use str(vic) to get the VICAR label content represented as a string.

Here are the steps to create and write a VICAR image file:

import vicar
vic = vicar.VicarImage()
vic.array = array
vic.prefix = prefix
vic.binheader = binheader
vic['NOTES'] = ['add as many more VICAR parameters', 'as you wish']
vic.write_file("path/to/file")

Contributing

Information on contributing to this package can be found in the Contributing Guide.

Links

• Documentation
• Repository
• Issue tracker
• PyPi

Licensing

This code is licensed under the Apache License v2.0.