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:mod:`jpeg` --- Read and write JPEG files
=========================================

.. module:: jpeg
   :platform: IRIX
   :synopsis: Read and write image files in compressed JPEG format.
   :deprecated:

.. deprecated:: 2.6
   The :mod:`jpeg` module has been removed in Python 3.

.. index:: single: Independent JPEG Group

The module :mod:`jpeg` provides access to the jpeg compressor and decompressor
written by the Independent JPEG Group (IJG). JPEG is a standard for compressing
pictures; it is defined in ISO 10918.  For details on JPEG or the Independent
JPEG Group software refer to the JPEG standard or the documentation provided
with the software.

.. index::
   single: Python Imaging Library
   single: PIL (the Python Imaging Library)
   single: Lundh, Fredrik

A portable interface to JPEG image files is available with the Python Imaging
Library (PIL) by Fredrik Lundh.  Information on PIL is available at
http://www.pythonware.com/products/pil/.

The :mod:`jpeg` module defines an exception and some functions.

.. exception:: error

Exception raised by :func:`compress` and :func:`decompress` in case of errors.

.. function:: compress(data, w, h, b)

.. index:: single: JFIF

Treat data as a pixmap of width *w* and height *h*, with *b* bytes per pixel.
   The data is in SGI GL order, so the first pixel is in the lower-left corner.
   This means that :func:`gl.lrectread` return data can immediately be passed to
   :func:`compress`. Currently only 1 byte and 4 byte pixels are allowed, the
   former being treated as greyscale and the latter as RGB color. :func:`compress`
   returns a string that contains the compressed picture, in JFIF format.

.. function:: decompress(data)

.. index:: single: JFIF

Data is a string containing a picture in JFIF format. It returns a tuple
   ``(data, width, height, bytesperpixel)``.  Again, the data is suitable to pass
   to :func:`gl.lrectwrite`.

.. function:: setoption(name, value)

Set various options.  Subsequent :func:`compress` and :func:`decompress` calls
   will use these options.  The following options are available:

.. seealso::

JPEG Still Image Data Compression Standard
      The canonical reference for the JPEG image format, by Pennebaker and Mitchell.

`Information Technology - Digital Compression and Coding of Continuous-tone Still Images - Requirements and Guidelines <http://www.w3.org/Graphics/JPEG/itu-t81.pdf>`_
      The ISO standard for JPEG is also published as ITU T.81.  This is available
      online in PDF form.