Edit File: jpeg.txt
: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 deprecated for removal in Python 3.0. .. 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: +-----------------+---------------------------------------------+ | Option | Effect | +=================+=============================================+ | ``'forcegray'`` | Force output to be grayscale, even if input | | | is RGB. | +-----------------+---------------------------------------------+ | ``'quality'`` | Set the quality of the compressed image to | | | a value between ``0`` and ``100`` (default | | | is ``75``). This only affects compression. | +-----------------+---------------------------------------------+ | ``'optimize'`` | Perform Huffman table optimization. Takes | | | longer, but results in smaller compressed | | | image. This only affects compression. | +-----------------+---------------------------------------------+ | ``'smooth'`` | Perform inter-block smoothing on | | | uncompressed image. Only useful for low- | | | quality images. This only affects | | | decompression. | +-----------------+---------------------------------------------+ .. 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.
Back to File Manager