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<div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span> <span class="comment">//</span></div><div class="line"><a name="l00002"></a><span class="lineno"> 2</span> <span class="comment">// Copyright 2019 Miral Shah <miralshah2211@gmail.com></span></div><div class="line"><a name="l00003"></a><span class="lineno"> 3</span> <span class="comment">//</span></div><div class="line"><a name="l00004"></a><span class="lineno"> 4</span> <span class="comment">// Use, modification and distribution are subject to the Boost Software License,</span></div><div class="line"><a name="l00005"></a><span class="lineno"> 5</span> <span class="comment">// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at</span></div><div class="line"><a name="l00006"></a><span class="lineno"> 6</span> <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> <span class="comment">//</span></div><div class="line"><a name="l00008"></a><span class="lineno"> 8</span> <span class="preprocessor">#ifndef BOOST_GIL_IMAGE_PROCESSING_THRESHOLD_HPP</span></div><div class="line"><a name="l00009"></a><span class="lineno"> 9</span> <span class="preprocessor">#define BOOST_GIL_IMAGE_PROCESSING_THRESHOLD_HPP</span></div><div class="line"><a name="l00010"></a><span class="lineno"> 10</span> </div><div class="line"><a name="l00011"></a><span class="lineno"> 11</span> <span class="preprocessor">#include <limits></span></div><div class="line"><a name="l00012"></a><span class="lineno"> 12</span> <span class="preprocessor">#include <array></span></div><div class="line"><a name="l00013"></a><span class="lineno"> 13</span> <span class="preprocessor">#include <type_traits></span></div><div class="line"><a name="l00014"></a><span class="lineno"> 14</span> <span class="preprocessor">#include <boost/gil/image.hpp></span></div><div class="line"><a name="l00015"></a><span class="lineno"> 15</span> </div><div class="line"><a name="l00016"></a><span class="lineno"> 16</span> <span class="keyword">namespace </span><a class="code" href="namespaceboost.html">boost</a> { <span class="keyword">namespace </span>gil {</div><div class="line"><a name="l00017"></a><span class="lineno"> 17</span> </div><div class="line"><a name="l00018"></a><span class="lineno"> 18</span> </div><div class="line"><a name="l00019"></a><span class="lineno"> 19</span> <span class="keyword">namespace </span>detail {</div><div class="line"><a name="l00020"></a><span class="lineno"> 20</span> </div><div class="line"><a name="l00021"></a><span class="lineno"> 21</span> <span class="keyword">template</span></div><div class="line"><a name="l00022"></a><span class="lineno"> 22</span> <</div><div class="line"><a name="l00023"></a><span class="lineno"> 23</span>  <span class="keyword">typename</span> SourceChannelT,</div><div class="line"><a name="l00024"></a><span class="lineno"> 24</span>  <span class="keyword">typename</span> ResultChannelT,</div><div class="line"><a name="l00025"></a><span class="lineno"> 25</span>  <span class="keyword">typename</span> SrcView,</div><div class="line"><a name="l00026"></a><span class="lineno"> 26</span>  <span class="keyword">typename</span> DstView,</div><div class="line"><a name="l00027"></a><span class="lineno"> 27</span>  <span class="keyword">typename</span> Operator</div><div class="line"><a name="l00028"></a><span class="lineno"> 28</span> ></div><div class="line"><a name="l00029"></a><span class="lineno"> 29</span> <span class="keywordtype">void</span> threshold_impl(SrcView <span class="keyword">const</span>& src_view, DstView <span class="keyword">const</span>& dst_view, Operator <span class="keyword">const</span>& threshold_op)</div><div class="line"><a name="l00030"></a><span class="lineno"> 30</span> {</div><div class="line"><a name="l00031"></a><span class="lineno"> 31</span>  gil_function_requires<ImageViewConcept<SrcView>>();</div><div class="line"><a name="l00032"></a><span class="lineno"> 32</span>  gil_function_requires<MutableImageViewConcept<DstView>>();</div><div class="line"><a name="l00033"></a><span class="lineno"> 33</span>  gil_function_requires<ColorSpacesCompatibleConcept</div><div class="line"><a name="l00034"></a><span class="lineno"> 34</span>  <</div><div class="line"><a name="l00035"></a><span class="lineno"> 35</span>  <span class="keyword">typename</span> color_space_type<SrcView>::type,</div><div class="line"><a name="l00036"></a><span class="lineno"> 36</span>  <span class="keyword">typename</span> color_space_type<DstView>::type></div><div class="line"><a name="l00037"></a><span class="lineno"> 37</span>  >();</div><div class="line"><a name="l00038"></a><span class="lineno"> 38</span>  static_assert(color_spaces_are_compatible</div><div class="line"><a name="l00039"></a><span class="lineno"> 39</span>  <</div><div class="line"><a name="l00040"></a><span class="lineno"> 40</span>  <span class="keyword">typename</span> color_space_type<SrcView>::type,</div><div class="line"><a name="l00041"></a><span class="lineno"> 41</span>  <span class="keyword">typename</span> color_space_type<DstView>::type</div><div class="line"><a name="l00042"></a><span class="lineno"> 42</span>  >::value, <span class="stringliteral">"Source and destination views must have pixels with the same color space"</span>);</div><div class="line"><a name="l00043"></a><span class="lineno"> 43</span> </div><div class="line"><a name="l00044"></a><span class="lineno"> 44</span>  <span class="comment">//iterate over the image chaecking each pixel value for the threshold</span></div><div class="line"><a name="l00045"></a><span class="lineno"> 45</span>  <span class="keywordflow">for</span> (std::ptrdiff_t y = 0; y < src_view.height(); y++)</div><div class="line"><a name="l00046"></a><span class="lineno"> 46</span>  {</div><div class="line"><a name="l00047"></a><span class="lineno"> 47</span>  <span class="keyword">typename</span> SrcView::x_iterator src_it = src_view.row_begin(y);</div><div class="line"><a name="l00048"></a><span class="lineno"> 48</span>  <span class="keyword">typename</span> DstView::x_iterator dst_it = dst_view.row_begin(y);</div><div class="line"><a name="l00049"></a><span class="lineno"> 49</span> </div><div class="line"><a name="l00050"></a><span class="lineno"> 50</span>  <span class="keywordflow">for</span> (std::ptrdiff_t x = 0; x < src_view.width(); x++)</div><div class="line"><a name="l00051"></a><span class="lineno"> 51</span>  {</div><div class="line"><a name="l00052"></a><span class="lineno"> 52</span>  static_transform(src_it[x], dst_it[x], threshold_op);</div><div class="line"><a name="l00053"></a><span class="lineno"> 53</span>  }</div><div class="line"><a name="l00054"></a><span class="lineno"> 54</span>  }</div><div class="line"><a name="l00055"></a><span class="lineno"> 55</span> }</div><div class="line"><a name="l00056"></a><span class="lineno"> 56</span> </div><div class="line"><a name="l00057"></a><span class="lineno"> 57</span> } <span class="comment">//namespace boost::gil::detail</span></div><div class="line"><a name="l00058"></a><span class="lineno"> 58</span> </div><div class="line"><a name="l00059"></a><span class="lineno"> 59</span> <span class="keyword">enum class</span> threshold_direction { regular, inverse };</div><div class="line"><a name="l00060"></a><span class="lineno"> 60</span> <span class="keyword">enum class</span> threshold_optimal_value { otsu, triangle };</div><div class="line"><a name="l00061"></a><span class="lineno"> 61</span> <span class="keyword">enum class</span> threshold_truncate_mode { threshold, zero };</div><div class="line"><a name="l00062"></a><span class="lineno"> 62</span> </div><div class="line"><a name="l00070"></a><span class="lineno"> 70</span> <span class="keyword">template</span> <<span class="keyword">typename</span> SrcView, <span class="keyword">typename</span> DstView></div><div class="line"><a name="l00071"></a><span class="lineno"> 71</span> <span class="keywordtype">void</span> threshold_binary</div><div class="line"><a name="l00072"></a><span class="lineno"> 72</span> (</div><div class="line"><a name="l00073"></a><span class="lineno"> 73</span>  SrcView <span class="keyword">const</span>& src_view,</div><div class="line"><a name="l00074"></a><span class="lineno"> 74</span>  DstView <span class="keyword">const</span>& dst_view,</div><div class="line"><a name="l00075"></a><span class="lineno"> 75</span>  <span class="keyword">typename</span> channel_type<DstView>::type threshold_value,</div><div class="line"><a name="l00076"></a><span class="lineno"> 76</span>  <span class="keyword">typename</span> channel_type<DstView>::type max_value,</div><div class="line"><a name="l00077"></a><span class="lineno"> 77</span>  threshold_direction direction = threshold_direction::regular</div><div class="line"><a name="l00078"></a><span class="lineno"> 78</span> )</div><div class="line"><a name="l00079"></a><span class="lineno"> 79</span> {</div><div class="line"><a name="l00080"></a><span class="lineno"> 80</span>  <span class="comment">//deciding output channel type and creating functor</span></div><div class="line"><a name="l00081"></a><span class="lineno"> 81</span>  <span class="keyword">using</span> source_channel_t = <span class="keyword">typename</span> channel_type<SrcView>::type;</div><div class="line"><a name="l00082"></a><span class="lineno"> 82</span>  <span class="keyword">using</span> result_channel_t = <span class="keyword">typename</span> channel_type<DstView>::type;</div><div class="line"><a name="l00083"></a><span class="lineno"> 83</span> </div><div class="line"><a name="l00084"></a><span class="lineno"> 84</span>  <span class="keywordflow">if</span> (direction == threshold_direction::regular)</div><div class="line"><a name="l00085"></a><span class="lineno"> 85</span>  {</div><div class="line"><a name="l00086"></a><span class="lineno"> 86</span>  detail::threshold_impl<source_channel_t, result_channel_t>(src_view, dst_view,</div><div class="line"><a name="l00087"></a><span class="lineno"> 87</span>  [threshold_value, max_value](source_channel_t px) -> result_channel_t {</div><div class="line"><a name="l00088"></a><span class="lineno"> 88</span>  <span class="keywordflow">return</span> px > threshold_value ? max_value : 0;</div><div class="line"><a name="l00089"></a><span class="lineno"> 89</span>  });</div><div class="line"><a name="l00090"></a><span class="lineno"> 90</span>  }</div><div class="line"><a name="l00091"></a><span class="lineno"> 91</span>  <span class="keywordflow">else</span></div><div class="line"><a name="l00092"></a><span class="lineno"> 92</span>  {</div><div class="line"><a name="l00093"></a><span class="lineno"> 93</span>  detail::threshold_impl<source_channel_t, result_channel_t>(src_view, dst_view,</div><div class="line"><a name="l00094"></a><span class="lineno"> 94</span>  [threshold_value, max_value](source_channel_t px) -> result_channel_t {</div><div class="line"><a name="l00095"></a><span class="lineno"> 95</span>  <span class="keywordflow">return</span> px > threshold_value ? 0 : max_value;</div><div class="line"><a name="l00096"></a><span class="lineno"> 96</span>  });</div><div class="line"><a name="l00097"></a><span class="lineno"> 97</span>  }</div><div class="line"><a name="l00098"></a><span class="lineno"> 98</span> }</div><div class="line"><a name="l00099"></a><span class="lineno"> 99</span> </div><div class="line"><a name="l00107"></a><span class="lineno"> 107</span> <span class="keyword">template</span> <<span class="keyword">typename</span> SrcView, <span class="keyword">typename</span> DstView></div><div class="line"><a name="l00108"></a><span class="lineno"> 108</span> <span class="keywordtype">void</span> threshold_binary</div><div class="line"><a name="l00109"></a><span class="lineno"> 109</span> (</div><div class="line"><a name="l00110"></a><span class="lineno"> 110</span>  SrcView <span class="keyword">const</span>& src_view,</div><div class="line"><a name="l00111"></a><span class="lineno"> 111</span>  DstView <span class="keyword">const</span>& dst_view,</div><div class="line"><a name="l00112"></a><span class="lineno"> 112</span>  <span class="keyword">typename</span> channel_type<DstView>::type threshold_value,</div><div class="line"><a name="l00113"></a><span class="lineno"> 113</span>  threshold_direction direction = threshold_direction::regular</div><div class="line"><a name="l00114"></a><span class="lineno"> 114</span> )</div><div class="line"><a name="l00115"></a><span class="lineno"> 115</span> {</div><div class="line"><a name="l00116"></a><span class="lineno"> 116</span>  <span class="comment">//deciding output channel type and creating functor</span></div><div class="line"><a name="l00117"></a><span class="lineno"> 117</span>  <span class="keyword">using</span> result_channel_t = <span class="keyword">typename</span> channel_type<DstView>::type;</div><div class="line"><a name="l00118"></a><span class="lineno"> 118</span> </div><div class="line"><a name="l00119"></a><span class="lineno"> 119</span>  result_channel_t max_value = std::numeric_limits<result_channel_t>::max();</div><div class="line"><a name="l00120"></a><span class="lineno"> 120</span>  threshold_binary(src_view, dst_view, threshold_value, max_value, direction);</div><div class="line"><a name="l00121"></a><span class="lineno"> 121</span> }</div><div class="line"><a name="l00122"></a><span class="lineno"> 122</span> </div><div class="line"><a name="l00134"></a><span class="lineno"> 134</span> <span class="keyword">template</span> <<span class="keyword">typename</span> SrcView, <span class="keyword">typename</span> DstView></div><div class="line"><a name="l00135"></a><span class="lineno"> 135</span> <span class="keywordtype">void</span> threshold_truncate</div><div class="line"><a name="l00136"></a><span class="lineno"> 136</span> (</div><div class="line"><a name="l00137"></a><span class="lineno"> 137</span>  SrcView <span class="keyword">const</span>& src_view,</div><div class="line"><a name="l00138"></a><span class="lineno"> 138</span>  DstView <span class="keyword">const</span>& dst_view,</div><div class="line"><a name="l00139"></a><span class="lineno"> 139</span>  <span class="keyword">typename</span> channel_type<DstView>::type threshold_value,</div><div class="line"><a name="l00140"></a><span class="lineno"> 140</span>  threshold_truncate_mode mode = threshold_truncate_mode::threshold,</div><div class="line"><a name="l00141"></a><span class="lineno"> 141</span>  threshold_direction direction = threshold_direction::regular</div><div class="line"><a name="l00142"></a><span class="lineno"> 142</span> )</div><div class="line"><a name="l00143"></a><span class="lineno"> 143</span> {</div><div class="line"><a name="l00144"></a><span class="lineno"> 144</span>  <span class="comment">//deciding output channel type and creating functor</span></div><div class="line"><a name="l00145"></a><span class="lineno"> 145</span>  <span class="keyword">using</span> source_channel_t = <span class="keyword">typename</span> channel_type<SrcView>::type;</div><div class="line"><a name="l00146"></a><span class="lineno"> 146</span>  <span class="keyword">using</span> result_channel_t = <span class="keyword">typename</span> channel_type<DstView>::type;</div><div class="line"><a name="l00147"></a><span class="lineno"> 147</span> </div><div class="line"><a name="l00148"></a><span class="lineno"> 148</span>  std::function<result_channel_t(source_channel_t)> threshold_logic;</div><div class="line"><a name="l00149"></a><span class="lineno"> 149</span> </div><div class="line"><a name="l00150"></a><span class="lineno"> 150</span>  <span class="keywordflow">if</span> (mode == threshold_truncate_mode::threshold)</div><div class="line"><a name="l00151"></a><span class="lineno"> 151</span>  {</div><div class="line"><a name="l00152"></a><span class="lineno"> 152</span>  <span class="keywordflow">if</span> (direction == threshold_direction::regular)</div><div class="line"><a name="l00153"></a><span class="lineno"> 153</span>  {</div><div class="line"><a name="l00154"></a><span class="lineno"> 154</span>  detail::threshold_impl<source_channel_t, result_channel_t>(src_view, dst_view,</div><div class="line"><a name="l00155"></a><span class="lineno"> 155</span>  [threshold_value](source_channel_t px) -> result_channel_t {</div><div class="line"><a name="l00156"></a><span class="lineno"> 156</span>  <span class="keywordflow">return</span> px > threshold_value ? threshold_value : px;</div><div class="line"><a name="l00157"></a><span class="lineno"> 157</span>  });</div><div class="line"><a name="l00158"></a><span class="lineno"> 158</span>  }</div><div class="line"><a name="l00159"></a><span class="lineno"> 159</span>  <span class="keywordflow">else</span></div><div class="line"><a name="l00160"></a><span class="lineno"> 160</span>  {</div><div class="line"><a name="l00161"></a><span class="lineno"> 161</span>  detail::threshold_impl<source_channel_t, result_channel_t>(src_view, dst_view,</div><div class="line"><a name="l00162"></a><span class="lineno"> 162</span>  [threshold_value](source_channel_t px) -> result_channel_t {</div><div class="line"><a name="l00163"></a><span class="lineno"> 163</span>  <span class="keywordflow">return</span> px > threshold_value ? px : threshold_value;</div><div class="line"><a name="l00164"></a><span class="lineno"> 164</span>  });</div><div class="line"><a name="l00165"></a><span class="lineno"> 165</span>  }</div><div class="line"><a name="l00166"></a><span class="lineno"> 166</span>  }</div><div class="line"><a name="l00167"></a><span class="lineno"> 167</span>  <span class="keywordflow">else</span></div><div class="line"><a name="l00168"></a><span class="lineno"> 168</span>  {</div><div class="line"><a name="l00169"></a><span class="lineno"> 169</span>  <span class="keywordflow">if</span> (direction == threshold_direction::regular)</div><div class="line"><a name="l00170"></a><span class="lineno"> 170</span>  {</div><div class="line"><a name="l00171"></a><span class="lineno"> 171</span>  detail::threshold_impl<source_channel_t, result_channel_t>(src_view, dst_view,</div><div class="line"><a name="l00172"></a><span class="lineno"> 172</span>  [threshold_value](source_channel_t px) -> result_channel_t {</div><div class="line"><a name="l00173"></a><span class="lineno"> 173</span>  <span class="keywordflow">return</span> px > threshold_value ? px : 0;</div><div class="line"><a name="l00174"></a><span class="lineno"> 174</span>  });</div><div class="line"><a name="l00175"></a><span class="lineno"> 175</span>  }</div><div class="line"><a name="l00176"></a><span class="lineno"> 176</span>  <span class="keywordflow">else</span></div><div class="line"><a name="l00177"></a><span class="lineno"> 177</span>  {</div><div class="line"><a name="l00178"></a><span class="lineno"> 178</span>  detail::threshold_impl<source_channel_t, result_channel_t>(src_view, dst_view,</div><div class="line"><a name="l00179"></a><span class="lineno"> 179</span>  [threshold_value](source_channel_t px) -> result_channel_t {</div><div class="line"><a name="l00180"></a><span class="lineno"> 180</span>  <span class="keywordflow">return</span> px > threshold_value ? 0 : px;</div><div class="line"><a name="l00181"></a><span class="lineno"> 181</span>  });</div><div class="line"><a name="l00182"></a><span class="lineno"> 182</span>  }</div><div class="line"><a name="l00183"></a><span class="lineno"> 183</span>  }</div><div class="line"><a name="l00184"></a><span class="lineno"> 184</span> }</div><div class="line"><a name="l00185"></a><span class="lineno"> 185</span> </div><div class="line"><a name="l00186"></a><span class="lineno"> 186</span> <span class="keyword">namespace </span>detail{</div><div class="line"><a name="l00187"></a><span class="lineno"> 187</span> </div><div class="line"><a name="l00188"></a><span class="lineno"> 188</span> <span class="keyword">template</span> <<span class="keyword">typename</span> SrcView, <span class="keyword">typename</span> DstView></div><div class="line"><a name="l00189"></a><span class="lineno"> 189</span> <span class="keywordtype">void</span> otsu_impl(SrcView <span class="keyword">const</span>& src_view, DstView <span class="keyword">const</span>& dst_view, threshold_direction direction)</div><div class="line"><a name="l00190"></a><span class="lineno"> 190</span> {</div><div class="line"><a name="l00191"></a><span class="lineno"> 191</span>  <span class="comment">//deciding output channel type and creating functor</span></div><div class="line"><a name="l00192"></a><span class="lineno"> 192</span>  <span class="keyword">using</span> source_channel_t = <span class="keyword">typename</span> channel_type<SrcView>::type;</div><div class="line"><a name="l00193"></a><span class="lineno"> 193</span> </div><div class="line"><a name="l00194"></a><span class="lineno"> 194</span>  std::array<std::size_t, 256> histogram{};</div><div class="line"><a name="l00195"></a><span class="lineno"> 195</span>  <span class="comment">//initial value of min is set to maximum possible value to compare histogram data</span></div><div class="line"><a name="l00196"></a><span class="lineno"> 196</span>  <span class="comment">//initial value of max is set to minimum possible value to compare histogram data</span></div><div class="line"><a name="l00197"></a><span class="lineno"> 197</span>  <span class="keyword">auto</span> min = std::numeric_limits<source_channel_t>::max(),</div><div class="line"><a name="l00198"></a><span class="lineno"> 198</span>  max = std::numeric_limits<source_channel_t>::min();</div><div class="line"><a name="l00199"></a><span class="lineno"> 199</span> </div><div class="line"><a name="l00200"></a><span class="lineno"> 200</span>  <span class="keywordflow">if</span> (<span class="keyword">sizeof</span>(source_channel_t) > 1 || std::is_signed<source_channel_t>::value)</div><div class="line"><a name="l00201"></a><span class="lineno"> 201</span>  {</div><div class="line"><a name="l00202"></a><span class="lineno"> 202</span>  <span class="comment">//iterate over the image to find the min and max pixel values</span></div><div class="line"><a name="l00203"></a><span class="lineno"> 203</span>  <span class="keywordflow">for</span> (std::ptrdiff_t y = 0; y < src_view.height(); y++)</div><div class="line"><a name="l00204"></a><span class="lineno"> 204</span>  {</div><div class="line"><a name="l00205"></a><span class="lineno"> 205</span>  <span class="keyword">typename</span> SrcView::x_iterator src_it = src_view.row_begin(y);</div><div class="line"><a name="l00206"></a><span class="lineno"> 206</span>  <span class="keywordflow">for</span> (std::ptrdiff_t x = 0; x < src_view.width(); x++)</div><div class="line"><a name="l00207"></a><span class="lineno"> 207</span>  {</div><div class="line"><a name="l00208"></a><span class="lineno"> 208</span>  <span class="keywordflow">if</span> (src_it[x] < min) min = src_it[x];</div><div class="line"><a name="l00209"></a><span class="lineno"> 209</span>  <span class="keywordflow">if</span> (src_it[x] > min) min = src_it[x];</div><div class="line"><a name="l00210"></a><span class="lineno"> 210</span>  }</div><div class="line"><a name="l00211"></a><span class="lineno"> 211</span>  }</div><div class="line"><a name="l00212"></a><span class="lineno"> 212</span> </div><div class="line"><a name="l00213"></a><span class="lineno"> 213</span>  <span class="comment">//making histogram</span></div><div class="line"><a name="l00214"></a><span class="lineno"> 214</span>  <span class="keywordflow">for</span> (std::ptrdiff_t y = 0; y < src_view.height(); y++)</div><div class="line"><a name="l00215"></a><span class="lineno"> 215</span>  {</div><div class="line"><a name="l00216"></a><span class="lineno"> 216</span>  <span class="keyword">typename</span> SrcView::x_iterator src_it = src_view.row_begin(y);</div><div class="line"><a name="l00217"></a><span class="lineno"> 217</span> </div><div class="line"><a name="l00218"></a><span class="lineno"> 218</span>  <span class="keywordflow">for</span> (std::ptrdiff_t x = 0; x < src_view.width(); x++)</div><div class="line"><a name="l00219"></a><span class="lineno"> 219</span>  {</div><div class="line"><a name="l00220"></a><span class="lineno"> 220</span>  histogram[((src_it[x] - min) * 255) / (max - min)]++;</div><div class="line"><a name="l00221"></a><span class="lineno"> 221</span>  }</div><div class="line"><a name="l00222"></a><span class="lineno"> 222</span>  }</div><div class="line"><a name="l00223"></a><span class="lineno"> 223</span>  }</div><div class="line"><a name="l00224"></a><span class="lineno"> 224</span>  <span class="keywordflow">else</span></div><div class="line"><a name="l00225"></a><span class="lineno"> 225</span>  {</div><div class="line"><a name="l00226"></a><span class="lineno"> 226</span>  <span class="comment">//making histogram</span></div><div class="line"><a name="l00227"></a><span class="lineno"> 227</span>  <span class="keywordflow">for</span> (std::ptrdiff_t y = 0; y < src_view.height(); y++)</div><div class="line"><a name="l00228"></a><span class="lineno"> 228</span>  {</div><div class="line"><a name="l00229"></a><span class="lineno"> 229</span>  <span class="keyword">typename</span> SrcView::x_iterator src_it = src_view.row_begin(y);</div><div class="line"><a name="l00230"></a><span class="lineno"> 230</span> </div><div class="line"><a name="l00231"></a><span class="lineno"> 231</span>  <span class="keywordflow">for</span> (std::ptrdiff_t x = 0; x < src_view.width(); x++)</div><div class="line"><a name="l00232"></a><span class="lineno"> 232</span>  {</div><div class="line"><a name="l00233"></a><span class="lineno"> 233</span>  histogram[src_it[x]]++;</div><div class="line"><a name="l00234"></a><span class="lineno"> 234</span>  }</div><div class="line"><a name="l00235"></a><span class="lineno"> 235</span>  }</div><div class="line"><a name="l00236"></a><span class="lineno"> 236</span>  }</div><div class="line"><a name="l00237"></a><span class="lineno"> 237</span> </div><div class="line"><a name="l00238"></a><span class="lineno"> 238</span>  <span class="comment">//histData = histogram data</span></div><div class="line"><a name="l00239"></a><span class="lineno"> 239</span>  <span class="comment">//sum = total (background + foreground)</span></div><div class="line"><a name="l00240"></a><span class="lineno"> 240</span>  <span class="comment">//sumB = sum background</span></div><div class="line"><a name="l00241"></a><span class="lineno"> 241</span>  <span class="comment">//wB = weight background</span></div><div class="line"><a name="l00242"></a><span class="lineno"> 242</span>  <span class="comment">//wf = weight foreground</span></div><div class="line"><a name="l00243"></a><span class="lineno"> 243</span>  <span class="comment">//varMax = tracking the maximum known value of between class variance</span></div><div class="line"><a name="l00244"></a><span class="lineno"> 244</span>  <span class="comment">//mB = mu background</span></div><div class="line"><a name="l00245"></a><span class="lineno"> 245</span>  <span class="comment">//mF = mu foreground</span></div><div class="line"><a name="l00246"></a><span class="lineno"> 246</span>  <span class="comment">//varBeetween = between class variance</span></div><div class="line"><a name="l00247"></a><span class="lineno"> 247</span>  <span class="comment">//http://www.labbookpages.co.uk/software/imgProc/otsuThreshold.html</span></div><div class="line"><a name="l00248"></a><span class="lineno"> 248</span>  <span class="comment">//https://www.ipol.im/pub/art/2016/158/</span></div><div class="line"><a name="l00249"></a><span class="lineno"> 249</span>  std::ptrdiff_t total_pixel = src_view.height() * src_view.width();</div><div class="line"><a name="l00250"></a><span class="lineno"> 250</span>  std::ptrdiff_t sum_total = 0, sum_back = 0;</div><div class="line"><a name="l00251"></a><span class="lineno"> 251</span>  std::size_t weight_back = 0, weight_fore = 0, threshold = 0;</div><div class="line"><a name="l00252"></a><span class="lineno"> 252</span>  <span class="keywordtype">double</span> var_max = 0, mean_back, mean_fore, var_intra_class;</div><div class="line"><a name="l00253"></a><span class="lineno"> 253</span> </div><div class="line"><a name="l00254"></a><span class="lineno"> 254</span>  <span class="keywordflow">for</span> (std::size_t t = 0; t < 256; t++)</div><div class="line"><a name="l00255"></a><span class="lineno"> 255</span>  {</div><div class="line"><a name="l00256"></a><span class="lineno"> 256</span>  sum_total += t * histogram[t];</div><div class="line"><a name="l00257"></a><span class="lineno"> 257</span>  }</div><div class="line"><a name="l00258"></a><span class="lineno"> 258</span> </div><div class="line"><a name="l00259"></a><span class="lineno"> 259</span>  <span class="keywordflow">for</span> (<span class="keywordtype">int</span> t = 0; t < 256; t++)</div><div class="line"><a name="l00260"></a><span class="lineno"> 260</span>  {</div><div class="line"><a name="l00261"></a><span class="lineno"> 261</span>  weight_back += histogram[t]; <span class="comment">// Weight Background</span></div><div class="line"><a name="l00262"></a><span class="lineno"> 262</span>  <span class="keywordflow">if</span> (weight_back == 0) <span class="keywordflow">continue</span>;</div><div class="line"><a name="l00263"></a><span class="lineno"> 263</span> </div><div class="line"><a name="l00264"></a><span class="lineno"> 264</span>  weight_fore = total_pixel - weight_back; <span class="comment">// Weight Foreground</span></div><div class="line"><a name="l00265"></a><span class="lineno"> 265</span>  <span class="keywordflow">if</span> (weight_fore == 0) <span class="keywordflow">break</span>;</div><div class="line"><a name="l00266"></a><span class="lineno"> 266</span> </div><div class="line"><a name="l00267"></a><span class="lineno"> 267</span>  sum_back += t * histogram[t];</div><div class="line"><a name="l00268"></a><span class="lineno"> 268</span> </div><div class="line"><a name="l00269"></a><span class="lineno"> 269</span>  mean_back = sum_back / weight_back; <span class="comment">// Mean Background</span></div><div class="line"><a name="l00270"></a><span class="lineno"> 270</span>  mean_fore = (sum_total - sum_back) / weight_fore; <span class="comment">// Mean Foreground</span></div><div class="line"><a name="l00271"></a><span class="lineno"> 271</span> </div><div class="line"><a name="l00272"></a><span class="lineno"> 272</span>  <span class="comment">// Calculate Between Class Variance</span></div><div class="line"><a name="l00273"></a><span class="lineno"> 273</span>  var_intra_class = weight_back * weight_fore * (mean_back - mean_fore) * (mean_back - mean_fore);</div><div class="line"><a name="l00274"></a><span class="lineno"> 274</span> </div><div class="line"><a name="l00275"></a><span class="lineno"> 275</span>  <span class="comment">// Check if new maximum found</span></div><div class="line"><a name="l00276"></a><span class="lineno"> 276</span>  <span class="keywordflow">if</span> (var_intra_class > var_max) {</div><div class="line"><a name="l00277"></a><span class="lineno"> 277</span>  var_max = var_intra_class;</div><div class="line"><a name="l00278"></a><span class="lineno"> 278</span>  threshold = t;</div><div class="line"><a name="l00279"></a><span class="lineno"> 279</span>  }</div><div class="line"><a name="l00280"></a><span class="lineno"> 280</span>  }</div><div class="line"><a name="l00281"></a><span class="lineno"> 281</span>  <span class="keywordflow">if</span> (<span class="keyword">sizeof</span>(source_channel_t) > 1 && std::is_unsigned<source_channel_t>::value)</div><div class="line"><a name="l00282"></a><span class="lineno"> 282</span>  {</div><div class="line"><a name="l00283"></a><span class="lineno"> 283</span>  threshold_binary(src_view, dst_view, (threshold * (max - min) / 255) + min, direction);</div><div class="line"><a name="l00284"></a><span class="lineno"> 284</span>  }</div><div class="line"><a name="l00285"></a><span class="lineno"> 285</span>  <span class="keywordflow">else</span> {</div><div class="line"><a name="l00286"></a><span class="lineno"> 286</span>  threshold_binary(src_view, dst_view, threshold, direction);</div><div class="line"><a name="l00287"></a><span class="lineno"> 287</span>  }</div><div class="line"><a name="l00288"></a><span class="lineno"> 288</span> }</div><div class="line"><a name="l00289"></a><span class="lineno"> 289</span> } <span class="comment">//namespace detail</span></div><div class="line"><a name="l00290"></a><span class="lineno"> 290</span> </div><div class="line"><a name="l00291"></a><span class="lineno"> 291</span> <span class="keyword">template</span> <<span class="keyword">typename</span> SrcView, <span class="keyword">typename</span> DstView></div><div class="line"><a name="l00292"></a><span class="lineno"> 292</span> <span class="keywordtype">void</span> threshold_optimal</div><div class="line"><a name="l00293"></a><span class="lineno"> 293</span> (</div><div class="line"><a name="l00294"></a><span class="lineno"> 294</span>  SrcView <span class="keyword">const</span>& src_view,</div><div class="line"><a name="l00295"></a><span class="lineno"> 295</span>  DstView <span class="keyword">const</span>& dst_view,</div><div class="line"><a name="l00296"></a><span class="lineno"> 296</span>  threshold_optimal_value mode = threshold_optimal_value::otsu,</div><div class="line"><a name="l00297"></a><span class="lineno"> 297</span>  threshold_direction direction = threshold_direction::regular</div><div class="line"><a name="l00298"></a><span class="lineno"> 298</span> )</div><div class="line"><a name="l00299"></a><span class="lineno"> 299</span> {</div><div class="line"><a name="l00300"></a><span class="lineno"> 300</span>  <span class="keywordflow">if</span> (mode == threshold_optimal_value::otsu)</div><div class="line"><a name="l00301"></a><span class="lineno"> 301</span>  {</div><div class="line"><a name="l00302"></a><span class="lineno"> 302</span>  <span class="keywordflow">for</span> (std::size_t i = 0; i < src_view.num_channels(); i++)</div><div class="line"><a name="l00303"></a><span class="lineno"> 303</span>  {</div><div class="line"><a name="l00304"></a><span class="lineno"> 304</span>  detail::otsu_impl</div><div class="line"><a name="l00305"></a><span class="lineno"> 305</span>  (nth_channel_view(src_view, i), nth_channel_view(dst_view, i), direction);</div><div class="line"><a name="l00306"></a><span class="lineno"> 306</span>  }</div><div class="line"><a name="l00307"></a><span class="lineno"> 307</span>  }</div><div class="line"><a name="l00308"></a><span class="lineno"> 308</span> }</div><div class="line"><a name="l00309"></a><span class="lineno"> 309</span> </div><div class="line"><a name="l00310"></a><span class="lineno"> 310</span> }} <span class="comment">//namespace boost::gil</span></div><div class="line"><a name="l00311"></a><span class="lineno"> 311</span> </div><div class="line"><a name="l00312"></a><span class="lineno"> 312</span> <span class="preprocessor">#endif //BOOST_GIL_IMAGE_PROCESSING_THRESHOLD_HPP</span></div><div class="ttc" id="namespaceboost_html"><div class="ttname"><a href="namespaceboost.html">boost</a></div><div class="ttdef"><b>Definition:</b> algorithm.hpp:30</div></div>
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