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  50 <div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno">    1</span>&#160;<span class="comment">//</span></div><div class="line"><a name="l00002"></a><span class="lineno">    2</span>&#160;<span class="comment">// Copyright 2014 Bill Gallafent</span></div><div class="line"><a name="l00003"></a><span class="lineno">    3</span>&#160;<span class="comment">//</span></div><div class="line"><a name="l00004"></a><span class="lineno">    4</span>&#160;<span class="comment">// Distributed under the Boost Software License, Version 1.0</span></div><div class="line"><a name="l00005"></a><span class="lineno">    5</span>&#160;<span class="comment">// See accompanying file LICENSE_1_0.txt or copy at</span></div><div class="line"><a name="l00006"></a><span class="lineno">    6</span>&#160;<span class="comment">// http://www.boost.org/LICENSE_1_0.txt</span></div><div class="line"><a name="l00007"></a><span class="lineno">    7</span>&#160;<span class="comment">//</span></div><div class="line"><a name="l00008"></a><span class="lineno">    8</span>&#160;<span class="preprocessor">#ifndef BOOST_GIL_PREMULTIPLY_HPP</span></div><div class="line"><a name="l00009"></a><span class="lineno">    9</span>&#160;<span class="preprocessor">#define BOOST_GIL_PREMULTIPLY_HPP</span></div><div class="line"><a name="l00010"></a><span class="lineno">   10</span>&#160;</div><div class="line"><a name="l00011"></a><span class="lineno">   11</span>&#160;<span class="preprocessor">#include &lt;boost/gil/rgba.hpp&gt;</span></div><div class="line"><a name="l00012"></a><span class="lineno">   12</span>&#160;<span class="preprocessor">#include &lt;boost/gil/detail/mp11.hpp&gt;</span></div><div class="line"><a name="l00013"></a><span class="lineno">   13</span>&#160;</div><div class="line"><a name="l00014"></a><span class="lineno">   14</span>&#160;<span class="preprocessor">#include &lt;boost/core/ignore_unused.hpp&gt;</span></div><div class="line"><a name="l00015"></a><span class="lineno">   15</span>&#160;</div><div class="line"><a name="l00016"></a><span class="lineno">   16</span>&#160;<span class="preprocessor">#include &lt;type_traits&gt;</span></div><div class="line"><a name="l00017"></a><span class="lineno">   17</span>&#160;</div><div class="line"><a name="l00018"></a><span class="lineno">   18</span>&#160;<span class="keyword">namespace </span>boost { <span class="keyword">namespace </span>gil {</div><div class="line"><a name="l00019"></a><span class="lineno">   19</span>&#160;</div><div class="line"><a name="l00020"></a><span class="lineno">   20</span>&#160;<span class="keyword">template</span> &lt;<span class="keyword">typename</span> SrcP, <span class="keyword">typename</span> DstP&gt;</div><div class="line"><a name="l00021"></a><span class="lineno">   21</span>&#160;<span class="keyword">struct </span>channel_premultiply</div><div class="line"><a name="l00022"></a><span class="lineno">   22</span>&#160;{</div><div class="line"><a name="l00023"></a><span class="lineno">   23</span>&#160;    channel_premultiply(SrcP <span class="keyword">const</span> &amp; src, DstP &amp; dst)</div><div class="line"><a name="l00024"></a><span class="lineno">   24</span>&#160;        : src_(src), dst_(dst)</div><div class="line"><a name="l00025"></a><span class="lineno">   25</span>&#160;    {}</div><div class="line"><a name="l00026"></a><span class="lineno">   26</span>&#160;</div><div class="line"><a name="l00027"></a><span class="lineno">   27</span>&#160;    <span class="keyword">template</span> &lt;<span class="keyword">typename</span> Channel&gt;</div><div class="line"><a name="l00028"></a><span class="lineno">   28</span>&#160;    <span class="keywordtype">void</span> operator()(Channel <span class="comment">/* channel */</span>)<span class="keyword"> const</span></div><div class="line"><a name="l00029"></a><span class="lineno">   29</span>&#160;<span class="keyword">    </span>{</div><div class="line"><a name="l00030"></a><span class="lineno">   30</span>&#160;        <span class="comment">// TODO: Explain why &#39;channel&#39; input paramater is not used, or used as tag only.</span></div><div class="line"><a name="l00031"></a><span class="lineno">   31</span>&#160;</div><div class="line"><a name="l00032"></a><span class="lineno">   32</span>&#160;        <span class="comment">// @todo: need to do a &quot;channel_convert&quot; too, in case the channel types aren&#39;t the same?</span></div><div class="line"><a name="l00033"></a><span class="lineno">   33</span>&#160;        <a class="code" href="group___color_base_algorithm_color.html#gab2d1dda637cb2b7c32cc87f199ea1dc0">get_color</a>(dst_, Channel()) = <a class="code" href="group___channel_multiply_algorithm.html#ga0af81efbbb77846afe2570f242d2b974">channel_multiply</a>(<a class="code" href="group___color_base_algorithm_color.html#gab2d1dda637cb2b7c32cc87f199ea1dc0">get_color</a>(src_,Channel()), alpha_or_max(src_));</div><div class="line"><a name="l00034"></a><span class="lineno">   34</span>&#160;    }</div><div class="line"><a name="l00035"></a><span class="lineno">   35</span>&#160;    SrcP <span class="keyword">const</span> &amp; src_;</div><div class="line"><a name="l00036"></a><span class="lineno">   36</span>&#160;    DstP &amp; dst_;</div><div class="line"><a name="l00037"></a><span class="lineno">   37</span>&#160;};</div><div class="line"><a name="l00038"></a><span class="lineno">   38</span>&#160;</div><div class="line"><a name="l00039"></a><span class="lineno">   39</span>&#160;<span class="keyword">namespace </span>detail</div><div class="line"><a name="l00040"></a><span class="lineno">   40</span>&#160;{</div><div class="line"><a name="l00041"></a><span class="lineno">   41</span>&#160;    <span class="keyword">template</span> &lt;<span class="keyword">typename</span> SrcP, <span class="keyword">typename</span> DstP&gt;</div><div class="line"><a name="l00042"></a><span class="lineno">   42</span>&#160;    <span class="keywordtype">void</span> assign_alpha_if(std::true_type, SrcP <span class="keyword">const</span> &amp;src, DstP &amp;dst)</div><div class="line"><a name="l00043"></a><span class="lineno">   43</span>&#160;    {</div><div class="line"><a name="l00044"></a><span class="lineno">   44</span>&#160;        <a class="code" href="group___color_base_algorithm_color.html#gab2d1dda637cb2b7c32cc87f199ea1dc0">get_color</a>(dst,alpha_t()) = alpha_or_max(src);</div><div class="line"><a name="l00045"></a><span class="lineno">   45</span>&#160;    }</div><div class="line"><a name="l00046"></a><span class="lineno">   46</span>&#160;</div><div class="line"><a name="l00047"></a><span class="lineno">   47</span>&#160;    <span class="keyword">template</span> &lt;<span class="keyword">typename</span> SrcP, <span class="keyword">typename</span> DstP&gt;</div><div class="line"><a name="l00048"></a><span class="lineno">   48</span>&#160;    <span class="keywordtype">void</span> assign_alpha_if(std::false_type, SrcP <span class="keyword">const</span>&amp; src, DstP&amp; dst)</div><div class="line"><a name="l00049"></a><span class="lineno">   49</span>&#160;    {</div><div class="line"><a name="l00050"></a><span class="lineno">   50</span>&#160;        <span class="comment">// nothing to do</span></div><div class="line"><a name="l00051"></a><span class="lineno">   51</span>&#160;        boost::ignore_unused(src);</div><div class="line"><a name="l00052"></a><span class="lineno">   52</span>&#160;        boost::ignore_unused(dst);</div><div class="line"><a name="l00053"></a><span class="lineno">   53</span>&#160;    }</div><div class="line"><a name="l00054"></a><span class="lineno">   54</span>&#160;}</div><div class="line"><a name="l00055"></a><span class="lineno">   55</span>&#160;</div><div class="line"><a name="l00056"></a><span class="lineno">   56</span>&#160;<span class="keyword">struct </span>premultiply</div><div class="line"><a name="l00057"></a><span class="lineno">   57</span>&#160;{</div><div class="line"><a name="l00058"></a><span class="lineno">   58</span>&#160;    <span class="keyword">template</span> &lt;<span class="keyword">typename</span> SrcP, <span class="keyword">typename</span> DstP&gt;</div><div class="line"><a name="l00059"></a><span class="lineno">   59</span>&#160;    <span class="keywordtype">void</span> operator()(<span class="keyword">const</span> SrcP&amp; src, DstP&amp; dst)<span class="keyword"> const</span></div><div class="line"><a name="l00060"></a><span class="lineno">   60</span>&#160;<span class="keyword">    </span>{</div><div class="line"><a name="l00061"></a><span class="lineno">   61</span>&#160;        <span class="keyword">using</span> src_colour_space_t = <span class="keyword">typename</span> color_space_type&lt;SrcP&gt;::type;</div><div class="line"><a name="l00062"></a><span class="lineno">   62</span>&#160;        <span class="keyword">using</span> dst_colour_space_t = <span class="keyword">typename</span> color_space_type&lt;DstP&gt;::type;</div><div class="line"><a name="l00063"></a><span class="lineno">   63</span>&#160;        <span class="keyword">using</span> src_colour_channels = mp11::mp_remove&lt;src_colour_space_t, alpha_t&gt;;</div><div class="line"><a name="l00064"></a><span class="lineno">   64</span>&#160;</div><div class="line"><a name="l00065"></a><span class="lineno">   65</span>&#160;        <span class="keyword">using</span> has_alpha_t = std::integral_constant&lt;bool, mp11::mp_contains&lt;dst_colour_space_t, alpha_t&gt;::value&gt;;</div><div class="line"><a name="l00066"></a><span class="lineno">   66</span>&#160;        mp11::mp_for_each&lt;src_colour_channels&gt;(channel_premultiply&lt;SrcP, DstP&gt;(src, dst));</div><div class="line"><a name="l00067"></a><span class="lineno">   67</span>&#160;        detail::assign_alpha_if(has_alpha_t(), src, dst);</div><div class="line"><a name="l00068"></a><span class="lineno">   68</span>&#160;    }</div><div class="line"><a name="l00069"></a><span class="lineno">   69</span>&#160;};</div><div class="line"><a name="l00070"></a><span class="lineno">   70</span>&#160;</div><div class="line"><a name="l00071"></a><span class="lineno">   71</span>&#160;<span class="keyword">template</span> &lt;<span class="keyword">typename</span> SrcConstRefP,  <span class="comment">// const reference to the source pixel</span></div><div class="line"><a name="l00072"></a><span class="lineno">   72</span>&#160;          <span class="keyword">typename</span> DstP&gt;          <span class="comment">// Destination pixel value (models PixelValueConcept)</span></div><div class="line"><a name="l00073"></a><span class="lineno">   73</span>&#160;<span class="keyword">class </span>premultiply_deref_fn</div><div class="line"><a name="l00074"></a><span class="lineno">   74</span>&#160;{</div><div class="line"><a name="l00075"></a><span class="lineno">   75</span>&#160;<span class="keyword">public</span>:</div><div class="line"><a name="l00076"></a><span class="lineno">   76</span>&#160;    <span class="keyword">using</span> const_t = premultiply_deref_fn&lt;SrcConstRefP, DstP&gt;;</div><div class="line"><a name="l00077"></a><span class="lineno">   77</span>&#160;    <span class="keyword">using</span> value_type = DstP;</div><div class="line"><a name="l00078"></a><span class="lineno">   78</span>&#160;    <span class="keyword">using</span> reference = value_type;      <span class="comment">// read-only dereferencing</span></div><div class="line"><a name="l00079"></a><span class="lineno">   79</span>&#160;    <span class="keyword">using</span> const_reference = <span class="keyword">const</span> value_type &amp;;</div><div class="line"><a name="l00080"></a><span class="lineno">   80</span>&#160;    <span class="keyword">using</span> argument_type = SrcConstRefP;</div><div class="line"><a name="l00081"></a><span class="lineno">   81</span>&#160;    <span class="keyword">using</span> result_type = reference;</div><div class="line"><a name="l00082"></a><span class="lineno">   82</span>&#160;    <span class="keyword">static</span> constexpr <span class="keywordtype">bool</span> is_mutable = <span class="keyword">false</span>;</div><div class="line"><a name="l00083"></a><span class="lineno">   83</span>&#160;</div><div class="line"><a name="l00084"></a><span class="lineno">   84</span>&#160;    result_type operator()(argument_type srcP)<span class="keyword"> const</span></div><div class="line"><a name="l00085"></a><span class="lineno">   85</span>&#160;<span class="keyword">    </span>{</div><div class="line"><a name="l00086"></a><span class="lineno">   86</span>&#160;        result_type dstP;</div><div class="line"><a name="l00087"></a><span class="lineno">   87</span>&#160;        premultiply()(srcP,dstP);</div><div class="line"><a name="l00088"></a><span class="lineno">   88</span>&#160;        <span class="keywordflow">return</span> dstP;</div><div class="line"><a name="l00089"></a><span class="lineno">   89</span>&#160;    }</div><div class="line"><a name="l00090"></a><span class="lineno">   90</span>&#160;};</div><div class="line"><a name="l00091"></a><span class="lineno">   91</span>&#160;</div><div class="line"><a name="l00092"></a><span class="lineno">   92</span>&#160;<span class="keyword">template</span> &lt;<span class="keyword">typename</span> SrcView, <span class="keyword">typename</span> DstP&gt;</div><div class="line"><a name="l00093"></a><span class="lineno">   93</span>&#160;<span class="keyword">struct </span>premultiplied_view_type</div><div class="line"><a name="l00094"></a><span class="lineno">   94</span>&#160;{</div><div class="line"><a name="l00095"></a><span class="lineno">   95</span>&#160;<span class="keyword">private</span>:</div><div class="line"><a name="l00096"></a><span class="lineno">   96</span>&#160;    <span class="keyword">using</span> src_pix_ref = <span class="keyword">typename</span> SrcView::const_t::reference;  <span class="comment">// const reference to pixel in SrcView</span></div><div class="line"><a name="l00097"></a><span class="lineno">   97</span>&#160;    <span class="keyword">using</span> deref_t = premultiply_deref_fn&lt;src_pix_ref, DstP&gt;; <span class="comment">// the dereference adaptor that performs color conversion</span></div><div class="line"><a name="l00098"></a><span class="lineno">   98</span>&#160;    <span class="keyword">using</span> add_ref_t = <span class="keyword">typename</span> SrcView::template add_deref&lt;deref_t&gt;;</div><div class="line"><a name="l00099"></a><span class="lineno">   99</span>&#160;<span class="keyword">public</span>:</div><div class="line"><a name="l00100"></a><span class="lineno">  100</span>&#160;    <span class="keyword">using</span> type = <span class="keyword">typename</span> add_ref_t::type; <span class="comment">// the color converted view type</span></div><div class="line"><a name="l00101"></a><span class="lineno">  101</span>&#160;    <span class="keyword">static</span> type make(<span class="keyword">const</span> SrcView&amp; sv) { <span class="keywordflow">return</span> add_ref_t::make(sv, deref_t()); }</div><div class="line"><a name="l00102"></a><span class="lineno">  102</span>&#160;};</div><div class="line"><a name="l00103"></a><span class="lineno">  103</span>&#160;</div><div class="line"><a name="l00104"></a><span class="lineno">  104</span>&#160;<span class="keyword">template</span> &lt;<span class="keyword">typename</span> DstP, <span class="keyword">typename</span> View&gt; <span class="keyword">inline</span></div><div class="line"><a name="l00105"></a><span class="lineno">  105</span>&#160;<span class="keyword">typename</span> premultiplied_view_type&lt;View,DstP&gt;::type premultiply_view(<span class="keyword">const</span> View&amp; src)</div><div class="line"><a name="l00106"></a><span class="lineno">  106</span>&#160;{</div><div class="line"><a name="l00107"></a><span class="lineno">  107</span>&#160;    <span class="keywordflow">return</span> premultiplied_view_type&lt;View,DstP&gt;::make(src);</div><div class="line"><a name="l00108"></a><span class="lineno">  108</span>&#160;}</div><div class="line"><a name="l00109"></a><span class="lineno">  109</span>&#160;</div><div class="line"><a name="l00110"></a><span class="lineno">  110</span>&#160;}} <span class="comment">// namespace boost::gil</span></div><div class="line"><a name="l00111"></a><span class="lineno">  111</span>&#160;</div><div class="line"><a name="l00112"></a><span class="lineno">  112</span>&#160;<span class="preprocessor">#endif</span></div><div class="ttc" id="group___channel_multiply_algorithm_html_ga0af81efbbb77846afe2570f242d2b974"><div class="ttname"><a href="group___channel_multiply_algorithm.html#ga0af81efbbb77846afe2570f242d2b974">boost::gil::channel_multiply</a></div><div class="ttdeci">channel_traits&lt; Channel &gt;::value_type channel_multiply(Channel a, Channel b)</div><div class="ttdoc">A function multiplying two channels. result = a * b / max_value.</div><div class="ttdef"><b>Definition:</b> channel_algorithm.hpp:539</div></div>
  51 <div class="ttc" id="group___color_base_algorithm_color_html_gab2d1dda637cb2b7c32cc87f199ea1dc0"><div class="ttname"><a href="group___color_base_algorithm_color.html#gab2d1dda637cb2b7c32cc87f199ea1dc0">boost::gil::get_color</a></div><div class="ttdeci">color_element_reference_type&lt; ColorBase, Color &gt;::type get_color(ColorBase &amp;cb, Color=Color())</div><div class="ttdoc">Mutable accessor to the element associated with a given color name.</div><div class="ttdef"><b>Definition:</b> color_base_algorithm.hpp:190</div></div>
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