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SGI IRIX Specific Services</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body"> <div class="section" id="module-jpeg"> <h1>38.12. <tt class="xref docutils literal"><span class="pre">jpeg</span></tt> — Read and write JPEG files<a class="headerlink" href="#module-jpeg" title="Permalink to this headline">¶</a></h1> <p><em>Platforms: </em>IRIX</p> <p class="deprecated"> <span class="versionmodified">Deprecated since version 2.6: </span>The <tt class="xref docutils literal"><span class="pre">jpeg</span></tt> module has been deprecated for removal in Python 3.0.</p> <p id="index-407">The module <tt class="xref docutils literal"><span class="pre">jpeg</span></tt> 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.</p> <p id="index-408">A portable interface to JPEG image files is available with the Python Imaging Library (PIL) by Fredrik Lundh. Information on PIL is available at <a class="reference external" href="http://www.pythonware.com/products/pil/">http://www.pythonware.com/products/pil/</a>.</p> <p>The <tt class="xref docutils literal"><span class="pre">jpeg</span></tt> module defines an exception and some functions.</p> <dl class="exception"> <dt id="jpeg.error"> <em class="property">exception </em><tt class="descclassname">jpeg.</tt><tt class="descname">error</tt><a class="headerlink" href="#jpeg.error" title="Permalink to this definition">¶</a></dt> <dd>Exception raised by <a title="jpeg.compress" class="reference internal" href="#jpeg.compress"><tt class="xref docutils literal"><span class="pre">compress()</span></tt></a> and <a title="jpeg.decompress" class="reference internal" href="#jpeg.decompress"><tt class="xref docutils literal"><span class="pre">decompress()</span></tt></a> in case of errors.</dd></dl> <dl class="function"> <dt id="jpeg.compress"> <tt class="descclassname">jpeg.</tt><tt class="descname">compress</tt><big>(</big><em>data</em>, <em>w</em>, <em>h</em>, <em>b</em><big>)</big><a class="headerlink" href="#jpeg.compress" title="Permalink to this definition">¶</a></dt> <dd><p id="index-409">Treat data as a pixmap of width <em>w</em> and height <em>h</em>, with <em>b</em> bytes per pixel. The data is in SGI GL order, so the first pixel is in the lower-left corner. This means that <tt class="xref docutils literal"><span class="pre">gl.lrectread()</span></tt> return data can immediately be passed to <a title="jpeg.compress" class="reference internal" href="#jpeg.compress"><tt class="xref docutils literal"><span class="pre">compress()</span></tt></a>. Currently only 1 byte and 4 byte pixels are allowed, the former being treated as greyscale and the latter as RGB color. <a title="jpeg.compress" class="reference internal" href="#jpeg.compress"><tt class="xref docutils literal"><span class="pre">compress()</span></tt></a> returns a string that contains the compressed picture, in JFIF format.</p> </dd></dl> <dl class="function"> <dt id="jpeg.decompress"> <tt class="descclassname">jpeg.</tt><tt class="descname">decompress</tt><big>(</big><em>data</em><big>)</big><a class="headerlink" href="#jpeg.decompress" title="Permalink to this definition">¶</a></dt> <dd><p id="index-410">Data is a string containing a picture in JFIF format. It returns a tuple <tt class="docutils literal"><span class="pre">(data,</span> <span class="pre">width,</span> <span class="pre">height,</span> <span class="pre">bytesperpixel)</span></tt>. Again, the data is suitable to pass to <tt class="xref docutils literal"><span class="pre">gl.lrectwrite()</span></tt>.</p> </dd></dl> <dl class="function"> <dt id="jpeg.setoption"> <tt class="descclassname">jpeg.</tt><tt class="descname">setoption</tt><big>(</big><em>name</em>, <em>value</em><big>)</big><a class="headerlink" href="#jpeg.setoption" title="Permalink to this definition">¶</a></dt> <dd><p>Set various options. Subsequent <a title="jpeg.compress" class="reference internal" href="#jpeg.compress"><tt class="xref docutils literal"><span class="pre">compress()</span></tt></a> and <a title="jpeg.decompress" class="reference internal" href="#jpeg.decompress"><tt class="xref docutils literal"><span class="pre">decompress()</span></tt></a> calls will use these options. The following options are available:</p> <table border="1" class="docutils"> <colgroup> <col width="27%" /> <col width="73%" /> </colgroup> <thead valign="bottom"> <tr><th class="head">Option</th> <th class="head">Effect</th> </tr> </thead> <tbody valign="top"> <tr><td><tt class="docutils literal"><span class="pre">'forcegray'</span></tt></td> <td>Force output to be grayscale, even if input is RGB.</td> </tr> <tr><td><tt class="docutils literal"><span class="pre">'quality'</span></tt></td> <td>Set the quality of the compressed image to a value between <tt class="docutils literal"><span class="pre">0</span></tt> and <tt class="docutils literal"><span class="pre">100</span></tt> (default is <tt class="docutils literal"><span class="pre">75</span></tt>). This only affects compression.</td> </tr> <tr><td><tt class="docutils literal"><span class="pre">'optimize'</span></tt></td> <td>Perform Huffman table optimization. Takes longer, but results in smaller compressed image. This only affects compression.</td> </tr> <tr><td><tt class="docutils literal"><span class="pre">'smooth'</span></tt></td> <td>Perform inter-block smoothing on uncompressed image. Only useful for low- quality images. This only affects decompression.</td> </tr> </tbody> </table> </dd></dl> <div class="admonition-see-also admonition seealso"> <p class="first admonition-title">See also</p> <dl class="last docutils"> <dt>JPEG Still Image Data Compression Standard</dt> <dd>The canonical reference for the JPEG image format, by Pennebaker and Mitchell.</dd> <dt><a class="reference external" href="http://www.w3.org/Graphics/JPEG/itu-t81.pdf">Information Technology - Digital Compression and Coding of Continuous-tone Still Images - Requirements and Guidelines</a></dt> <dd>The ISO standard for JPEG is also published as ITU T.81. 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