1 2 3 4 5<!DOCTYPE html> 6<html lang="en"> 7<head> 8 <title>ImageMagick: MagickCore, C API for ImageMagick: Image Features</title> 9 <meta charset="utf-8" /> 10 <meta http-equiv="X-UA-Compatible" content="IE=edge" /> 11 <meta name="viewport" content="width=device-width, initial-scale=1" /> 12 <meta http-equiv="content-type" content="text/html; charset=utf-8"/> 13 <meta name="application-name" content="ImageMagick"/> 14 <meta name="description" content="ImageMagick® is a software suite to create, edit, compose, or convert bitmap images. It can read and write images in a variety of formats (over 200) including PNG, JPEG, JPEG-2000, GIF, WebP, Postscript, PDF, and SVG. 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The features include the angular second moment, contrast, correlation, sum of squares: variance, inverse difference moment, sum average, sum varience, sum entropy, entropy, difference variance, difference entropy, information measures of correlation 1, information measures of correlation 2, and maximum correlation coefficient. You can access the red channel contrast, for example, like this:</p> 108 109<pre class="text"> 110channel_features=GetImageFeatures(image,1,exception); 111contrast=channel_features[RedPixelChannel].contrast[0]; 112</pre> 113 114<p>Use MagickRelinquishMemory() to free the features buffer.</p> 115 116<p>The format of the GetImageFeatures method is:</p> 117 118<pre class="text"> 119ChannelFeatures *GetImageFeatures(const Image *image, 120 const size_t distance,ExceptionInfo *exception) 121</pre> 122 123<p>A description of each parameter follows:</p> 124 125<dd> 126</dd> 127 128<dd> </dd> 129<dl class="dl-horizontal"> 130<dt>image</dt> 131<dd>the image. </dd> 132 133<dd> </dd> 134<dt>distance</dt> 135<dd>the distance. </dd> 136 137<dd> </dd> 138<dt>exception</dt> 139<dd>return any errors or warnings in this structure. </dd> 140 141<dd> </dd> 142</dl> 143<h2><a href="http://www.imagemagick.org/api/MagickCore/feature_8c.html" id="Use_HoughLineImage">Use HoughLineImage</a></h2> 144 145<p>Use HoughLineImage() in conjunction with any binary edge extracted image (we recommand Canny) to identify lines in the image. The algorithm accumulates counts for every white pixel for every possible orientation (for angles from 0 to 179 in 1 degree increments) and distance from the center of the image to the corner (in 1 px increments) and stores the counts in an accumulator matrix of angle vs distance. The size of the accumulator is 180x(diagonal/2). Next it searches this space for peaks in counts and converts the locations of the peaks to slope and intercept in the normal x,y input image space. Use the slope/intercepts to find the endpoints clipped to the bounds of the image. The lines are then drawn. The counts are a measure of the length of the lines</p> 146 147<p>The format of the HoughLineImage method is:</p> 148 149<pre class="text"> 150Image *HoughLineImage(const Image *image,const size_t width, 151 const size_t height,const size_t threshold,ExceptionInfo *exception) 152</pre> 153 154<p>A description of each parameter follows:</p> 155 156<dd> 157</dd> 158 159<dd> </dd> 160<dl class="dl-horizontal"> 161<dt>image</dt> 162<dd>the image. </dd> 163 164<dd> </dd> 165<dt>width, height</dt> 166<dd>find line pairs as local maxima in this neighborhood. </dd> 167 168<dd> </dd> 169<dt>threshold</dt> 170<dd>the line count threshold. </dd> 171 172<dd> </dd> 173<dt>exception</dt> 174<dd>return any errors or warnings in this structure. </dd> 175 176<dd> </dd> 177</dl> 178<h2><a href="http://www.imagemagick.org/api/MagickCore/feature_8c.html" id="MeanShiftImage">MeanShiftImage</a></h2> 179 180<p>MeanShiftImage() delineate arbitrarily shaped clusters in the image. For each pixel, it visits all the pixels in the neighborhood specified by the window centered at the pixel and excludes those that are outside the radius=(window-1)/2 surrounding the pixel. From those pixels, it finds those that are within the specified color distance from the current mean, and computes a new x,y centroid from those coordinates and a new mean. This new x,y centroid is used as the center for a new window. This process iterates until it converges and the final mean is replaces the (original window center) pixel value. It repeats this process for the next pixel, etc., until it processes all pixels in the image. Results are typically better with colorspaces other than sRGB. We recommend YIQ, YUV or YCbCr.</p> 181 182<p>The format of the MeanShiftImage method is:</p> 183 184<pre class="text"> 185Image *MeanShiftImage(const Image *image,const size_t width, 186 const size_t height,const double color_distance, 187 ExceptionInfo *exception) 188</pre> 189 190<p>A description of each parameter follows:</p> 191 192<dd> 193</dd> 194 195<dd> </dd> 196<dl class="dl-horizontal"> 197<dt>image</dt> 198<dd>the image. </dd> 199 200<dd> </dd> 201<dt>width, height</dt> 202<dd>find pixels in this neighborhood. </dd> 203 204<dd> </dd> 205<dt>color_distance</dt> 206<dd>the color distance. </dd> 207 208<dd> </dd> 209<dt>exception</dt> 210<dd>return any errors or warnings in this structure. </dd> 211 212<dd> </dd> 213</dl> 214</div> 215 <footer class="magick-footer"> 216 <p><a href="../support.html">Donate</a> • 217 <a href="../sitemap.html">Sitemap</a> • 218 <a href="../links.html">Related</a> • 219 <a href="../architecture.html">Architecture</a> 220</p> 221 <p><a href="feature.html#">Back to top</a> • 222 <a href="http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x89AB63D48277377A">Public Key</a> • 223 <a href="http://www.imagemagick.org/script/contact.php">Contact Us</a></p> 224 <p><small>© 1999-2016 ImageMagick Studio LLC</small></p> 225 </footer> 226</div><!-- /.container --> 227 228 <script src="https://localhost/ajax/libs/jquery/1.11.3/jquery.min.js"></script> 229 <script src="../js/magick.html"></script> 230</div> 231</body> 232</html> 233
