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<section id="point">
<h1>Point<a class="headerlink" href="#point" title="Link to this heading"></a></h1>
<nav class="contents local" id="contents">
<ul class="simple">
<li><p><a class="reference internal" href="#overview" id="id1">Overview</a></p></li>
<li><p><a class="reference internal" href="#models" id="id2">Models</a></p></li>
</ul>
</nav>
<section id="overview">
<h2><a class="toc-backref" href="#id1" role="doc-backlink">Overview</a><a class="headerlink" href="#overview" title="Link to this heading"></a></h2>
<p>A point defines the location of a pixel inside an image. It can also be used
to describe the dimensions of an image. In most general terms, points are
N-dimensional and model the following concept:</p>
<div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span><span class="k">concept</span><span class="w"> </span><span class="nc">PointNDConcept</span><span class="o">&lt;</span><span class="k">typename</span><span class="w"> </span><span class="nc">T</span><span class="o">&gt;</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">Regular</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span>
<span class="p">{</span>
<span class="w"> </span><span class="c1">// the type of a coordinate along each axis</span>
<span class="w"> </span><span class="k">template</span><span class="w"> </span><span class="o">&lt;</span><span class="kt">size_t</span><span class="w"> </span><span class="n">K</span><span class="o">&gt;</span><span class="w"> </span><span class="k">struct</span><span class="w"> </span><span class="nc">axis</span><span class="p">;</span><span class="w"> </span><span class="n">where</span><span class="w"> </span><span class="n">Metafunction</span><span class="o">&lt;</span><span class="n">axis</span><span class="o">&gt;</span><span class="p">;</span>
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="kt">size_t</span><span class="w"> </span><span class="n">num_dimensions</span><span class="p">;</span>
<span class="w"> </span><span class="c1">// accessor/modifier of the value of each axis.</span>
<span class="w"> </span><span class="k">template</span><span class="w"> </span><span class="o">&lt;</span><span class="kt">size_t</span><span class="w"> </span><span class="n">K</span><span class="o">&gt;</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="k">typename</span><span class="w"> </span><span class="nc">axis</span><span class="o">&lt;</span><span class="n">K</span><span class="o">&gt;::</span><span class="n">type</span><span class="o">&amp;</span><span class="w"> </span><span class="n">T</span><span class="o">::</span><span class="n">axis_value</span><span class="p">()</span><span class="w"> </span><span class="k">const</span><span class="p">;</span>
<span class="w"> </span><span class="k">template</span><span class="w"> </span><span class="o">&lt;</span><span class="kt">size_t</span><span class="w"> </span><span class="n">K</span><span class="o">&gt;</span><span class="w"> </span><span class="k">typename</span><span class="w"> </span><span class="nc">axis</span><span class="o">&lt;</span><span class="n">K</span><span class="o">&gt;::</span><span class="n">type</span><span class="o">&amp;</span><span class="w"> </span><span class="n">T</span><span class="o">::</span><span class="n">axis_value</span><span class="p">();</span>
<span class="p">};</span>
</pre></div>
</div>
<p>GIL uses a two-dimensional point, which is a refinement of <code class="docutils literal notranslate"><span class="pre">PointNDConcept</span></code>
in which both dimensions are of the same type:</p>
<div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span><span class="k">concept</span><span class="w"> </span><span class="nc">Point2DConcept</span><span class="o">&lt;</span><span class="k">typename</span><span class="w"> </span><span class="nc">T</span><span class="o">&gt;</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">PointNDConcept</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span>
<span class="p">{</span>
<span class="w"> </span><span class="n">where</span><span class="w"> </span><span class="n">num_dimensions</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">2</span><span class="p">;</span>
<span class="w"> </span><span class="n">where</span><span class="w"> </span><span class="n">SameType</span><span class="o">&lt;</span><span class="n">axis</span><span class="o">&lt;</span><span class="mi">0</span><span class="o">&gt;::</span><span class="n">type</span><span class="p">,</span><span class="w"> </span><span class="n">axis</span><span class="o">&lt;</span><span class="mi">1</span><span class="o">&gt;::</span><span class="n">type</span><span class="o">&gt;</span><span class="p">;</span>
<span class="w"> </span><span class="k">typename</span><span class="w"> </span><span class="nc">value_type</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">axis</span><span class="o">&lt;</span><span class="mi">0</span><span class="o">&gt;::</span><span class="n">type</span><span class="p">;</span>
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">value_type</span><span class="o">&amp;</span><span class="w"> </span><span class="k">operator</span><span class="p">[](</span><span class="k">const</span><span class="w"> </span><span class="n">T</span><span class="o">&amp;</span><span class="p">,</span><span class="w"> </span><span class="kt">size_t</span><span class="w"> </span><span class="n">i</span><span class="p">);</span>
<span class="w"> </span><span class="n">value_type</span><span class="o">&amp;</span><span class="w"> </span><span class="k">operator</span><span class="p">[](</span><span class="w"> </span><span class="n">T</span><span class="o">&amp;</span><span class="p">,</span><span class="w"> </span><span class="kt">size_t</span><span class="w"> </span><span class="n">i</span><span class="p">);</span>
<span class="w"> </span><span class="n">value_type</span><span class="w"> </span><span class="n">x</span><span class="p">,</span><span class="n">y</span><span class="p">;</span>
<span class="p">};</span>
</pre></div>
</div>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<ul class="simple">
<li><p><a class="reference external" href="../reference/structboost_1_1gil_1_1_point_n_d_concept.html">PointNDConcept</a></p></li>
<li><p><a class="reference external" href="../reference/structboost_1_1gil_1_1_point2_d_concept.html">Point2DConcept</a></p></li>
</ul>
</div>
</section>
<section id="models">
<h2><a class="toc-backref" href="#id2" role="doc-backlink">Models</a><a class="headerlink" href="#models" title="Link to this heading"></a></h2>
<p>GIL provides a model of <code class="docutils literal notranslate"><span class="pre">Point2DConcept</span></code>, <code class="docutils literal notranslate"><span class="pre">point&lt;T&gt;</span></code> where <code class="docutils literal notranslate"><span class="pre">T</span></code> is the
coordinate type.</p>
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