2 :mod:`jpeg` --- Read and write JPEG files
3 =========================================
7 :synopsis: Read and write image files in compressed JPEG format.
11 The :mod:`jpeg` module has been deprecated for removal in Python 3.0.
15 .. index:: single: Independent JPEG Group
17 The module :mod:`jpeg` provides access to the jpeg compressor and decompressor
18 written by the Independent JPEG Group (IJG). JPEG is a standard for compressing
19 pictures; it is defined in ISO 10918. For details on JPEG or the Independent
20 JPEG Group software refer to the JPEG standard or the documentation provided
24 single: Python Imaging Library
25 single: PIL (the Python Imaging Library)
26 single: Lundh, Fredrik
28 A portable interface to JPEG image files is available with the Python Imaging
29 Library (PIL) by Fredrik Lundh. Information on PIL is available at
30 http://www.pythonware.com/products/pil/.
32 The :mod:`jpeg` module defines an exception and some functions.
37 Exception raised by :func:`compress` and :func:`decompress` in case of errors.
40 .. function:: compress(data, w, h, b)
42 .. index:: single: JFIF
44 Treat data as a pixmap of width *w* and height *h*, with *b* bytes per pixel.
45 The data is in SGI GL order, so the first pixel is in the lower-left corner.
46 This means that :func:`gl.lrectread` return data can immediately be passed to
47 :func:`compress`. Currently only 1 byte and 4 byte pixels are allowed, the
48 former being treated as greyscale and the latter as RGB color. :func:`compress`
49 returns a string that contains the compressed picture, in JFIF format.
52 .. function:: decompress(data)
54 .. index:: single: JFIF
56 Data is a string containing a picture in JFIF format. It returns a tuple
57 ``(data, width, height, bytesperpixel)``. Again, the data is suitable to pass
58 to :func:`gl.lrectwrite`.
61 .. function:: setoption(name, value)
63 Set various options. Subsequent :func:`compress` and :func:`decompress` calls
64 will use these options. The following options are available:
66 +-----------------+---------------------------------------------+
68 +=================+=============================================+
69 | ``'forcegray'`` | Force output to be grayscale, even if input |
71 +-----------------+---------------------------------------------+
72 | ``'quality'`` | Set the quality of the compressed image to |
73 | | a value between ``0`` and ``100`` (default |
74 | | is ``75``). This only affects compression. |
75 +-----------------+---------------------------------------------+
76 | ``'optimize'`` | Perform Huffman table optimization. Takes |
77 | | longer, but results in smaller compressed |
78 | | image. This only affects compression. |
79 +-----------------+---------------------------------------------+
80 | ``'smooth'`` | Perform inter-block smoothing on |
81 | | uncompressed image. Only useful for low- |
82 | | quality images. This only affects |
84 +-----------------+---------------------------------------------+
89 JPEG Still Image Data Compression Standard
90 The canonical reference for the JPEG image format, by Pennebaker and Mitchell.
92 `Information Technology - Digital Compression and Coding of Continuous-tone Still Images - Requirements and Guidelines <http://www.w3.org/Graphics/JPEG/itu-t81.pdf>`_
93 The ISO standard for JPEG is also published as ITU T.81. This is available