1 2 3 4 5<!doctype html> 6<html lang="en"> 7<head> 8 <meta charset="utf-8" /> 9 <meta name="viewport" content="width=device-width, initial-scale=1" /> 10 <title>ImageMagick - Connected Components Labeling</title> 11 <meta name="application-name" content="ImageMagick" /> 12 <meta name="description" content="Use ImageMagick® to create, edit, compose, and convert digital images. 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The labeling process scans the image, pixel-by-pixel from top-left to bottom-right, in order to identify connected pixel regions, i.e. regions of adjacent pixels which share the same set of intensity values. For example, let's find the objects in this image:</p> 96<ul> 97 <a href="../images/objects.gif"><img src="../images/objects.gif" width="256" height="171" class="image-slices" alt="purse" /></a> 98</ul> 99<p>To identify the objects in this image, use this command:</p> 100<ul><pre class="highlight"><code>magick objects.gif -connected-components 4 -auto-level -depth 8 objects.png</code></pre></ul> 101<p>The detected objects are uniquely labeled. Use auto leveling to visualize the detected objects:</p> 102<ul> 103 <a href="../images/objects.png"><img src="../images/objects.png" width="256" height="171" class="image-slices" alt="Objects" /></a> 104</ul> 105<p>Object statistics is useful to review. To display them, use this command:</p> 106<ul><pre class="highlight"><code>magick objects.gif -define connected-components:verbose=true -connected-components 4 objects.png</code></pre></ul> 107<p>Five objects were detected in the source image with these statistics:</p> 108<ul><pre class="highlight"><code>Objects (id: bounding-box centroid area mean-color): 109 0: 256x171+0+0 119.2,80.8 33117 srgb(0,0,0) 110 2: 120x135+104+18 159.5,106.5 8690 srgb(255,255,255) 111 3: 50x36+129+44 154.2,63.4 1529 srgb(0,0,0) 112 4: 21x23+0+45 8.8,55.9 409 srgb(255,255,255) 113 1: 4x10+252+0 253.9,4.1 31 srgb(255,255,255) 114</code></pre></ul> 115<p>Add <code>-define connected-components:exclude-header=true</code> to show the objects without the header-line. Add <code>-define connected-components:exclude-ids=true</code>.</p> 116<p>Use <code>-connected-components 8</code> to visit 8 neighbors rather than 4. By default, neighbor colors must be exact to be part of a unique object. Use the <a href="../www/command-line-options.html#fuzz">-fuzz</a> option to include pixels as part of an object that are <var>close</var> in color.</p> 117<p>You might want to eliminate small objects by merging them with their larger neighbors. If so, use this command:</p> 118<ul><pre class="highlight"><code>magick objects.gif -define connected-components:area-threshold=410 -connected-components 4 \ 119 -auto-level objects.jpg</code></pre></ul> 120<p>Here are the expected results. Notice, how the small objects are now merged with the background.</p> 121<ul> 122 <a href="../images/objects.jpg"><img src="../images/objects.jpg" width="256" height="171" class="image-slices" alt="Objects" /></a> 123</ul> 124<p>Notice how two of the objects were merged leaving three remaining objects:</p> 125<ul><pre class="highlight"><code>Objects (id: bounding-box centroid area mean-color): 126 0: 256x171+0+0 118.0,80.4 33557 srgb(0,0,0) 127 2: 120x135+104+18 159.5,106.5 8690 srgb(255,255,255) 128 3: 50x36+129+44 154.2,63.4 1529 srgb(0,0,0)</code></pre></ul> 129<p>By default, the labeled image is grayscale. You can instead replace the object color in the labeled image with the mean-color from the source image. Simply add this setting, <code>-define connected-components:mean-color=true</code>, to your command line.</p> 130<p>Thresholds can optionally include ranges, e.g. <code>-define connected-components:area-threshold=410-1600</code>. To keep the background object, identify it with <code>-define connected-components:background-id=<var>object-id</var></code>. The default background object is the object with the largest area.</p> 131<p>In addition to area, there is support for these thresholding metrics:</p> 132<ul> 133<li>connected-components:angle-threshold (from equivalent ellipse)</li> 134<li>connected-components:circularity-threshold (4*pi*area/perimeter^2)</li> 135<li>connected-components:diameter-threshold (sqrt(4*area/pi))</li> 136<li>connected-components:eccentricity-threshold (from equivalent ellipse)</li> 137<li>connected-components:major-axis-threshold (diameter from equivalent ellipse)</li> 138<li>connected-components:minor-axis-threshold (diameter from equivalent ellipse)</li> 139<li>connected-components:perimeter-threshold</li> 140</ul> 141<p>You may want to remove certain objects. Use <code>-define connected-components:remove-ids=<em>list-of-ids</em></code> (e.g. -define connected-components:remove-ids=2,4-5). Or use <code>-define connected-components:keep-ids=<em>list-of-ids</em></code> to keep these objects and merge all others. For convenience, you can keep the top objects with this option: <code>-define connected-components:keep-top=<em>number-of-objects</em></code>. Rather than object ids, you can instead remove or keep objects identified by there color, e.g. <code>-define connected-components:keep-colors=<em>red;green;blue</em></code>.</p> 142<p>Objects in your image may look homogeneous but have slightly different color values. By default, only pixels that match exactly are considered as part of a particular object. For slight variations of color in an object, use <code>-fuzz</code>. For example,</p> 143<ul><pre class="highlight"><code>magick star-map.png -fuzz 5% -define connected-components:verbose=true \ 144 -define connected-components:mean-color=true -connected-components 4 stars.gif</code></pre></ul> 145</div> 146 </div> 147 </main><!-- /.container --> 148 <footer class="magick-footer"> 149 <div class="container-fluid"> 150 <a href="../www/security-policy.html">Security</a> • 151 <a href="../www/news.html">News</a> 152 153 <a href="connected-components.html#"><img class="d-inline" id="wand" alt="And Now a Touch of Magick" width="16" height="16" src="../images/wand.ico"/></a> 154 155 <a href="../www/links.html">Related</a> • 156 <a href="../www/sitemap.html">Sitemap</a> 157 <br/> 158 <a href="../www/support.html">Sponsor</a> • 159 <a href="../www/cite.html">Cite</a> • 160 <a href="http://pgp.mit.edu/pks/lookup?op=get&search=0x89AB63D48277377A">Public Key</a> • 161 <a href="../www/https://imagemagick.org/script/contact.php">Contact Us</a> 162 <br/> 163 <a href="https://github.com/imagemagick/imagemagick" target="_blank" rel="noopener" aria-label="GitHub"><svg xmlns="http://www.w3.org/2000/svg" class="navbar-nav-svg" viewBox="0 0 512 499.36" width="2%" height="2%" role="img" focusable="false"><title>GitHub</title><path fill="currentColor" fill-rule="evenodd" d="M256 0C114.64 0 0 114.61 0 256c0 113.09 73.34 209 175.08 242.9 12.8 2.35 17.47-5.56 17.47-12.34 0-6.08-.22-22.18-.35-43.54-71.2 15.49-86.2-34.34-86.2-34.34-11.64-29.57-28.42-37.45-28.42-37.45-23.27-15.84 1.73-15.55 1.73-15.55 25.69 1.81 39.21 26.38 39.21 26.38 22.84 39.12 59.92 27.82 74.5 21.27 2.33-16.54 8.94-27.82 16.25-34.22-56.84-6.43-116.6-28.43-116.6-126.49 0-27.95 10-50.8 26.35-68.69-2.63-6.48-11.42-32.5 2.51-67.75 0 0 21.49-6.88 70.4 26.24a242.65 242.65 0 0 1 128.18 0c48.87-33.13 70.33-26.24 70.33-26.24 14 35.25 5.18 61.27 2.55 67.75 16.41 17.9 26.31 40.75 26.31 68.69 0 98.35-59.85 120-116.88 126.32 9.19 7.9 17.38 23.53 17.38 47.41 0 34.22-.31 61.83-.31 70.23 0 6.85 4.61 14.81 17.6 12.31C438.72 464.97 512 369.08 512 256.02 512 114.62 397.37 0 256 0z"/></svg></a> • 164 <a href="https://twitter.com/imagemagick" target="_blank" rel="noopener" aria-label="Twitter"><svg xmlns="http://www.w3.org/2000/svg" class="navbar-nav-svg" viewBox="0 0 512 416.32" width="2%" height="2%" role="img" focusable="false"><title>Twitter</title><path fill="currentColor" d="M160.83 416.32c193.2 0 298.92-160.22 298.92-298.92 0-4.51 0-9-.2-13.52A214 214 0 0 0 512 49.38a212.93 212.93 0 0 1-60.44 16.6 105.7 105.7 0 0 0 46.3-58.19 209 209 0 0 1-66.79 25.37 105.09 105.09 0 0 0-181.73 71.91 116.12 116.12 0 0 0 2.66 24c-87.28-4.3-164.73-46.3-216.56-109.82A105.48 105.48 0 0 0 68 159.6a106.27 106.27 0 0 1-47.53-13.11v1.43a105.28 105.28 0 0 0 84.21 103.06 105.67 105.67 0 0 1-47.33 1.84 105.06 105.06 0 0 0 98.14 72.94A210.72 210.72 0 0 1 25 370.84a202.17 202.17 0 0 1-25-1.43 298.85 298.85 0 0 0 160.83 46.92"/></svg></a> 165 <br/> 166 <small>© 1999-2021 ImageMagick Studio LLC</small> 167 </div> 168 </footer> 169 170 <!-- Javascript assets --> 171 <script src="assets/magick.js" ></script> 172 </body> 173</html> 174<!-- Magick Cache 13th February 2021 13:13 -->
