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<div class="section" id="image">
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<h1>Image</h1>
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<div class="contents local topic" id="contents">
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<ul class="simple">
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<li><a class="reference internal" href="#overview" id="id1">Overview</a></li>
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<li><a class="reference internal" href="#models" id="id2">Models</a></li>
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<div class="section" id="overview">
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<h2><a class="toc-backref" href="#id1">Overview</a></h2>
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<p>An image is a container that owns the pixels of a given image view
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It allocates them in its constructor and deletes them in the destructor.
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It has a deep assignment operator and copy constructor. Images are used
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rarely, just when data ownership is important. Most STL algorithms operate on
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ranges, not containers. Similarly most GIL algorithms operate on image views
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(which images provide).</p>
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<p>In the most general form images are N-dimensional and satisfy the following
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concept:</p>
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<div class="highlight-cpp"><div class="highlight"><pre><span class="n">concept</span> <span class="n">RandomAccessNDImageConcept</span><span class="o"><</span><span class="k">typename</span> <span class="n">Img</span><span class="o">></span> <span class="o">:</span> <span class="n">Regular</span><span class="o"><</span><span class="n">Img</span><span class="o">></span>
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<span class="p">{</span>
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<span class="k">typename</span> <span class="n">view_t</span><span class="p">;</span> <span class="n">where</span> <span class="n">MutableRandomAccessNDImageViewConcept</span><span class="o"><</span><span class="n">view_t</span><span class="o">></span><span class="p">;</span>
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<span class="k">typename</span> <span class="n">const_view_t</span> <span class="o">=</span> <span class="n">view_t</span><span class="o">::</span><span class="n">const_t</span><span class="p">;</span>
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<span class="k">typename</span> <span class="n">point_t</span> <span class="o">=</span> <span class="n">view_t</span><span class="o">::</span><span class="n">point_t</span><span class="p">;</span>
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<span class="k">typename</span> <span class="n">value_type</span> <span class="o">=</span> <span class="n">view_t</span><span class="o">::</span><span class="n">value_type</span><span class="p">;</span>
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<span class="k">typename</span> <span class="n">allocator_type</span><span class="p">;</span>
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<span class="n">Img</span><span class="o">::</span><span class="n">Img</span><span class="p">(</span><span class="n">point_t</span> <span class="n">dims</span><span class="p">,</span> <span class="n">std</span><span class="o">::</span><span class="kt">size_t</span> <span class="n">alignment</span><span class="o">=</span><span class="mi">0</span><span class="p">);</span>
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<span class="n">Img</span><span class="o">::</span><span class="n">Img</span><span class="p">(</span><span class="n">point_t</span> <span class="n">dims</span><span class="p">,</span> <span class="n">value_type</span> <span class="n">fill_value</span><span class="p">,</span> <span class="n">std</span><span class="o">::</span><span class="kt">size_t</span> <span class="n">alignment</span><span class="p">);</span>
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<span class="kt">void</span> <span class="n">Img</span><span class="o">::</span><span class="n">recreate</span><span class="p">(</span><span class="n">point_t</span> <span class="n">new_dims</span><span class="p">,</span> <span class="n">std</span><span class="o">::</span><span class="kt">size_t</span> <span class="n">alignment</span><span class="o">=</span><span class="mi">0</span><span class="p">);</span>
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<span class="kt">void</span> <span class="n">Img</span><span class="o">::</span><span class="n">recreate</span><span class="p">(</span><span class="n">point_t</span> <span class="n">new_dims</span><span class="p">,</span> <span class="n">value_type</span> <span class="n">fill_value</span><span class="p">,</span> <span class="n">std</span><span class="o">::</span><span class="kt">size_t</span> <span class="n">alignment</span><span class="p">);</span>
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<span class="k">const</span> <span class="n">point_t</span><span class="o">&</span> <span class="n">Img</span><span class="o">::</span><span class="n">dimensions</span><span class="p">()</span> <span class="k">const</span><span class="p">;</span>
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<span class="k">const</span> <span class="n">const_view_t</span><span class="o">&</span> <span class="n">const_view</span><span class="p">(</span><span class="k">const</span> <span class="n">Img</span><span class="o">&</span><span class="p">);</span>
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<span class="k">const</span> <span class="n">view_t</span><span class="o">&</span> <span class="n">view</span><span class="p">(</span><span class="n">Img</span><span class="o">&</span><span class="p">);</span>
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<span class="p">};</span>
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</pre></div>
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</div>
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<p>Two-dimensional images have additional requirements:</p>
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<div class="highlight-cpp"><div class="highlight"><pre><span class="n">concept</span> <span class="n">RandomAccess2DImageConcept</span><span class="o"><</span><span class="n">RandomAccessNDImageConcept</span> <span class="n">Img</span><span class="o">></span>
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<span class="p">{</span>
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<span class="k">typename</span> <span class="n">x_coord_t</span> <span class="o">=</span> <span class="n">const_view_t</span><span class="o">::</span><span class="n">x_coord_t</span><span class="p">;</span>
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<span class="k">typename</span> <span class="n">y_coord_t</span> <span class="o">=</span> <span class="n">const_view_t</span><span class="o">::</span><span class="n">y_coord_t</span><span class="p">;</span>
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<span class="n">Img</span><span class="o">::</span><span class="n">Img</span><span class="p">(</span><span class="n">x_coord_t</span> <span class="n">width</span><span class="p">,</span> <span class="n">y_coord_t</span> <span class="n">height</span><span class="p">,</span> <span class="n">std</span><span class="o">::</span><span class="kt">size_t</span> <span class="n">alignment</span><span class="o">=</span><span class="mi">0</span><span class="p">);</span>
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<span class="n">Img</span><span class="o">::</span><span class="n">Img</span><span class="p">(</span><span class="n">x_coord_t</span> <span class="n">width</span><span class="p">,</span> <span class="n">y_coord_t</span> <span class="n">height</span><span class="p">,</span> <span class="n">value_type</span> <span class="n">fill_value</span><span class="p">,</span> <span class="n">std</span><span class="o">::</span><span class="kt">size_t</span> <span class="n">alignment</span><span class="p">);</span>
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<span class="n">x_coord_t</span> <span class="n">Img</span><span class="o">::</span><span class="n">width</span><span class="p">()</span> <span class="k">const</span><span class="p">;</span>
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<span class="n">y_coord_t</span> <span class="n">Img</span><span class="o">::</span><span class="n">height</span><span class="p">()</span> <span class="k">const</span><span class="p">;</span>
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<span class="kt">void</span> <span class="n">Img</span><span class="o">::</span><span class="n">recreate</span><span class="p">(</span><span class="n">x_coord_t</span> <span class="n">width</span><span class="p">,</span> <span class="n">y_coord_t</span> <span class="n">height</span><span class="p">,</span> <span class="n">std</span><span class="o">::</span><span class="kt">size_t</span> <span class="n">alignment</span><span class="o">=</span><span class="mi">1</span><span class="p">);</span>
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<span class="kt">void</span> <span class="n">Img</span><span class="o">::</span><span class="n">recreate</span><span class="p">(</span><span class="n">x_coord_t</span> <span class="n">width</span><span class="p">,</span> <span class="n">y_coord_t</span> <span class="n">height</span><span class="p">,</span> <span class="n">value_type</span> <span class="n">fill_value</span><span class="p">,</span> <span class="n">std</span><span class="o">::</span><span class="kt">size_t</span> <span class="n">alignment</span><span class="p">);</span>
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<span class="p">};</span>
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</pre></div>
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</div>
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<p>GIL images have views that model <code class="docutils literal"><span class="pre">ImageViewConcept</span></code> and operate on pixels.</p>
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<div class="highlight-cpp"><div class="highlight"><pre><span class="n">concept</span> <span class="n">ImageConcept</span><span class="o"><</span><span class="n">RandomAccess2DImageConcept</span> <span class="n">Img</span><span class="o">></span>
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<span class="p">{</span>
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<span class="n">where</span> <span class="n">MutableImageViewConcept</span><span class="o"><</span><span class="n">view_t</span><span class="o">></span><span class="p">;</span>
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<span class="k">typename</span> <span class="n">coord_t</span> <span class="o">=</span> <span class="n">view_t</span><span class="o">::</span><span class="n">coord_t</span><span class="p">;</span>
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<span class="p">};</span>
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</pre></div>
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</div>
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<p>Images, unlike locators and image views, don’t have ‘mutable’ set of concepts
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because immutable images are not very useful.</p>
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<div class="admonition seealso">
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<p class="first admonition-title">See also</p>
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<ul class="last simple">
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<li><a class="reference external" href="reference/structboost_1_1gil_1_1_random_access_n_d_image_concept.html">RandomAccessNDImageConcept<Image></a></li>
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<li><a class="reference external" href="reference/structboost_1_1gil_1_1_random_access2_d_image_concept.html">RandomAccess2DImageConcept<Image></a></li>
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<li><a class="reference external" href="reference/structboost_1_1gil_1_1_image_concept.html">ImageConcept<Image></a></li>
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</ul>
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</div>
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</div>
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<div class="section" id="models">
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<h2><a class="toc-backref" href="#id2">Models</a></h2>
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<p>GIL provides a class, <code class="docutils literal"><span class="pre">image</span></code>, which is templated over the value type
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(the pixel) and models <code class="docutils literal"><span class="pre">ImageConcept</span></code>:</p>
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<div class="highlight-cpp"><div class="highlight"><pre> <span class="k">template</span>
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<span class="o"><</span>
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<span class="k">typename</span> <span class="n">Pixel</span><span class="p">,</span> <span class="c1">// Models PixelValueConcept</span>
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<span class="kt">bool</span> <span class="n">IsPlanar</span><span class="p">,</span> <span class="c1">// planar or interleaved image</span>
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<span class="k">typename</span> <span class="n">A</span><span class="o">=</span><span class="n">std</span><span class="o">::</span><span class="n">allocator</span><span class="o"><</span><span class="kt">unsigned</span> <span class="kt">char</span><span class="o">></span>
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<span class="o">></span>
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<span class="k">class</span> <span class="nc">image</span><span class="p">;</span>
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</pre></div>
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</div>
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<p>The image constructor takes an alignment parameter which allows for
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constructing images that are word-aligned or 8-byte aligned. The alignment is
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specified in bytes. The default value for alignment is 0, which means there is
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no padding at the end of rows. Many operations are faster using such
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1D-traversable images, because <code class="docutils literal"><span class="pre">image_view::x_iterator</span></code> can be used to
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traverse the pixels, instead of the more complicated <code class="docutils literal"><span class="pre">image_view::iterator</span></code>.
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Note that when alignment is 0, packed images are aligned to the bit - i.e.
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there are no padding bits at the end of rows of packed images.</p>
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Last updated on 2021-04-13 16:04:40.
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