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  • Committer: Dave Kuhlman
  • Date: 2017-04-15 16:24:56 UTC
  • Revision ID: dkuhlman@davekuhlman.org-20170415162456-iav9vozzg4iwqwv3
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python-2.7.11-docs-html/library/imghdr.html
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
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  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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  <head>
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    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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    <title>21.8. imghdr — Determine the type of an image &mdash; Python 2.7.11 documentation</title>
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    <link rel="stylesheet" href="../_static/classic.css" type="text/css" />
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    <link rel="stylesheet" href="../_static/pygments.css" type="text/css" />
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    <script type="text/javascript">
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      var DOCUMENTATION_OPTIONS = {
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        URL_ROOT:    '../',
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        VERSION:     '2.7.11',
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        COLLAPSE_INDEX: false,
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        FILE_SUFFIX: '.html',
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        HAS_SOURCE:  true
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      };
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    </script>
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    <script type="text/javascript" src="../_static/jquery.js"></script>
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    <script type="text/javascript" src="../_static/underscore.js"></script>
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          title="Search within Python 2.7.11 documentation"
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          href="../_static/opensearch.xml"/>
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    <link rel="author" title="About these documents" href="../about.html" />
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    <link rel="copyright" title="Copyright" href="../copyright.html" />
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    <link rel="top" title="Python 2.7.11 documentation" href="../contents.html" />
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    <link rel="up" title="21. Multimedia Services" href="mm.html" />
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    <link rel="next" title="21.9. sndhdr — Determine type of sound file" href="sndhdr.html" />
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             accesskey="I">index</a></li>
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             >modules</a> |</li>
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  <div class="section" id="module-imghdr">
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<span id="imghdr-determine-the-type-of-an-image"></span><h1>21.8. <a class="reference internal" href="#module-imghdr" title="imghdr: Determine the type of image contained in a file or byte stream."><code class="xref py py-mod docutils literal"><span class="pre">imghdr</span></code></a> &#8212; Determine the type of an image<a class="headerlink" href="#module-imghdr" title="Permalink to this headline">¶</a></h1>
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<p><strong>Source code:</strong> <a class="reference external" href="https://hg.python.org/cpython/file/2.7/Lib/imghdr.py">Lib/imghdr.py</a></p>
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<hr class="docutils" />
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<p>The <a class="reference internal" href="#module-imghdr" title="imghdr: Determine the type of image contained in a file or byte stream."><code class="xref py py-mod docutils literal"><span class="pre">imghdr</span></code></a> module determines the type of image contained in a file or
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byte stream.</p>
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<p>The <a class="reference internal" href="#module-imghdr" title="imghdr: Determine the type of image contained in a file or byte stream."><code class="xref py py-mod docutils literal"><span class="pre">imghdr</span></code></a> module defines the following function:</p>
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<dl class="function">
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<dt id="imghdr.what">
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<code class="descclassname">imghdr.</code><code class="descname">what</code><span class="sig-paren">(</span><em>filename</em><span class="optional">[</span>, <em>h</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#imghdr.what" title="Permalink to this definition">¶</a></dt>
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<dd><p>Tests the image data contained in the file named by <em>filename</em>, and returns a
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string describing the image type.  If optional <em>h</em> is provided, the <em>filename</em>
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is ignored and <em>h</em> is assumed to contain the byte stream to test.</p>
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</dd></dl>
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<p>The following image types are recognized, as listed below with the return value
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from <a class="reference internal" href="#imghdr.what" title="imghdr.what"><code class="xref py py-func docutils literal"><span class="pre">what()</span></code></a>:</p>
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<table border="1" class="docutils">
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<colgroup>
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<col width="26%" />
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<col width="74%" />
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</colgroup>
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<thead valign="bottom">
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<tr class="row-odd"><th class="head">Value</th>
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<th class="head">Image format</th>
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</tr>
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</thead>
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<tbody valign="top">
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<tr class="row-even"><td><code class="docutils literal"><span class="pre">'rgb'</span></code></td>
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<td>SGI ImgLib Files</td>
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</tr>
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<tr class="row-odd"><td><code class="docutils literal"><span class="pre">'gif'</span></code></td>
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<td>GIF 87a and 89a Files</td>
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</tr>
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<tr class="row-even"><td><code class="docutils literal"><span class="pre">'pbm'</span></code></td>
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<td>Portable Bitmap Files</td>
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</tr>
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<tr class="row-odd"><td><code class="docutils literal"><span class="pre">'pgm'</span></code></td>
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<td>Portable Graymap Files</td>
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</tr>
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<tr class="row-even"><td><code class="docutils literal"><span class="pre">'ppm'</span></code></td>
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<td>Portable Pixmap Files</td>
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</tr>
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<tr class="row-odd"><td><code class="docutils literal"><span class="pre">'tiff'</span></code></td>
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<td>TIFF Files</td>
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</tr>
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<tr class="row-even"><td><code class="docutils literal"><span class="pre">'rast'</span></code></td>
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<td>Sun Raster Files</td>
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</tr>
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<tr class="row-odd"><td><code class="docutils literal"><span class="pre">'xbm'</span></code></td>
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<td>X Bitmap Files</td>
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</tr>
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<tr class="row-even"><td><code class="docutils literal"><span class="pre">'jpeg'</span></code></td>
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<td>JPEG data in JFIF or Exif formats</td>
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</tr>
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<tr class="row-odd"><td><code class="docutils literal"><span class="pre">'bmp'</span></code></td>
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<td>BMP files</td>
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</tr>
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<tr class="row-even"><td><code class="docutils literal"><span class="pre">'png'</span></code></td>
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<td>Portable Network Graphics</td>
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</tr>
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</tbody>
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</table>
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<div class="versionadded">
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<p><span class="versionmodified">New in version 2.5: </span>Exif detection.</p>
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</div>
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<p>You can extend the list of file types <a class="reference internal" href="#module-imghdr" title="imghdr: Determine the type of image contained in a file or byte stream."><code class="xref py py-mod docutils literal"><span class="pre">imghdr</span></code></a> can recognize by appending
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to this variable:</p>
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<dl class="data">
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<dt id="imghdr.tests">
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<code class="descclassname">imghdr.</code><code class="descname">tests</code><a class="headerlink" href="#imghdr.tests" title="Permalink to this definition">¶</a></dt>
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<dd><p>A list of functions performing the individual tests.  Each function takes two
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arguments: the byte-stream and an open file-like object. When <a class="reference internal" href="#imghdr.what" title="imghdr.what"><code class="xref py py-func docutils literal"><span class="pre">what()</span></code></a> is
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called with a byte-stream, the file-like object will be <code class="docutils literal"><span class="pre">None</span></code>.</p>
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<p>The test function should return a string describing the image type if the test
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succeeded, or <code class="docutils literal"><span class="pre">None</span></code> if it failed.</p>
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</dd></dl>
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<p>Example:</p>
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<div class="highlight-python"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span> <span class="nn">imghdr</span>
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<span class="gp">&gt;&gt;&gt; </span><span class="n">imghdr</span><span class="o">.</span><span class="n">what</span><span class="p">(</span><span class="s1">&#39;bass.gif&#39;</span><span class="p">)</span>
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<span class="go">&#39;gif&#39;</span>
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</pre></div>
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</div>
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</div>
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  <p class="topless"><a href="colorsys.html"
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                        title="previous chapter">21.7. <code class="docutils literal"><span class="pre">colorsys</span></code> &#8212; Conversions between color systems</a></p>
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  <h4>Next topic</h4>
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                        title="next chapter">21.9. <code class="docutils literal"><span class="pre">sndhdr</span></code> &#8212; Determine type of sound file</a></p>
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