File: //var/chroot/usr/share/doc/ImageMagick-7/www/convex-hull.html
<!doctype html>
<html lang="en" data-bs-theme="auto">
<head>
<script src="assets/color-modes.js" ></script>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<title>ImageMagick – Convex Hull</title>
<meta name="keywords" content="convex, hull, ImageMagick, image processing, command-line tool, format conversion, photo editing" />
<meta name="description" content="Convex Hull" />
<meta name="application-name" content="ImageMagick" />
<meta name="application-url" content="https://imagemagick.org" />
<meta name="copyright" content="Copyright (c) 1999 ImageMagick Studio LLC" />
<meta itemprop='url' content='../' />
<meta itemprop='title' content='ImageMagick' />
<meta itemprop='description' content="ImageMagick is a free and open-source software suite used for editing and manipulating digital images. It provides a versatile set of tools for various image-related tasks. You can use ImageMagick to resize, convert, and apply various transformations to images. It supports a wide range of file formats, including JPEG, PNG, GIF, TIFF, and Ultra HDR." />
<meta property='og:url' content='../' />
<meta property='og:name' content='ImageMagick' />
<meta property='og:image' content='../images/logo.png' />
<meta property='og:type' content='website' />
<meta property='og:site_name' content='ImageMagick' />
<meta property='og:description' content="ImageMagick is a free and open-source software suite used for editing and manipulating digital images. It provides a versatile set of tools for various image-related tasks. You can use ImageMagick to resize, convert, and apply various transformations to images. It supports a wide range of file formats, including JPEG, PNG, GIF, TIFF, and Ultra HDR." />
<meta name="google-site-verification" content="_bMOCDpkx9ZAzBwb2kF3PRHbfUUdFj2uO8Jd1AXArz4" />
<link type="images/png" sizes="64x64" href="../images/wand.png" rel="icon" />
<link type="images/icon" sizes="16x16" href="../images/wand.ico" rel="shortcut icon" />
<link href="convex-hull.html" rel="canonical" />
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@docsearch/css@3" />
<link href="assets/magick.css" rel="stylesheet" />
<script async src="https://localhost/pagead/js/adsbygoogle.js?client=ca-pub-3129977114552745" crossorigin="anonymous"></script>
</head>
<body>
<svg xmlns="http://www.w3.org/2000/svg" class="d-none">
<symbol id="check2" viewBox="0 0 16 16">
<path d="M13.854 3.646a.5.5 0 0 1 0 .708l-7 7a.5.5 0 0 1-.708 0l-3.5-3.5a.5.5 0 1 1 .708-.708L6.5 10.293l6.646-6.647a.5.5 0 0 1 .708 0z"/>
</symbol>
<symbol id="circle-half" viewBox="0 0 16 16">
<path d="M8 15A7 7 0 1 0 8 1v14zm0 1A8 8 0 1 1 8 0a8 8 0 0 1 0 16z"/>
</symbol>
<symbol id="moon-stars-fill" viewBox="0 0 16 16">
<path d="M6 .278a.768.768 0 0 1 .08.858 7.208 7.208 0 0 0-.878 3.46c0 4.021 3.278 7.277 7.318 7.277.527 0 1.04-.055 1.533-.16a.787.787 0 0 1 .81.316.733.733 0 0 1-.031.893A8.349 8.349 0 0 1 8.344 16C3.734 16 0 12.286 0 7.71 0 4.266 2.114 1.312 5.124.06A.752.752 0 0 1 6 .278z"/>
<path d="M10.794 3.148a.217.217 0 0 1 .412 0l.387 1.162c.173.518.579.924 1.097 1.097l1.162.387a.217.217 0 0 1 0 .412l-1.162.387a1.734 1.734 0 0 0-1.097 1.097l-.387 1.162a.217.217 0 0 1-.412 0l-.387-1.162A1.734 1.734 0 0 0 9.31 6.593l-1.162-.387a.217.217 0 0 1 0-.412l1.162-.387a1.734 1.734 0 0 0 1.097-1.097l.387-1.162zM13.863.099a.145.145 0 0 1 .274 0l.258.774c.115.346.386.617.732.732l.774.258a.145.145 0 0 1 0 .274l-.774.258a1.156 1.156 0 0 0-.732.732l-.258.774a.145.145 0 0 1-.274 0l-.258-.774a1.156 1.156 0 0 0-.732-.732l-.774-.258a.145.145 0 0 1 0-.274l.774-.258c.346-.115.617-.386.732-.732L13.863.1z"/>
</symbol>
<symbol id="sun-fill" viewBox="0 0 16 16">
<path d="M8 12a4 4 0 1 0 0-8 4 4 0 0 0 0 8zM8 0a.5.5 0 0 1 .5.5v2a.5.5 0 0 1-1 0v-2A.5.5 0 0 1 8 0zm0 13a.5.5 0 0 1 .5.5v2a.5.5 0 0 1-1 0v-2A.5.5 0 0 1 8 13zm8-5a.5.5 0 0 1-.5.5h-2a.5.5 0 0 1 0-1h2a.5.5 0 0 1 .5.5zM3 8a.5.5 0 0 1-.5.5h-2a.5.5 0 0 1 0-1h2A.5.5 0 0 1 3 8zm10.657-5.657a.5.5 0 0 1 0 .707l-1.414 1.415a.5.5 0 1 1-.707-.708l1.414-1.414a.5.5 0 0 1 .707 0zm-9.193 9.193a.5.5 0 0 1 0 .707L3.05 13.657a.5.5 0 0 1-.707-.707l1.414-1.414a.5.5 0 0 1 .707 0zm9.193 2.121a.5.5 0 0 1-.707 0l-1.414-1.414a.5.5 0 0 1 .707-.707l1.414 1.414a.5.5 0 0 1 0 .707zM4.464 4.465a.5.5 0 0 1-.707 0L2.343 3.05a.5.5 0 1 1 .707-.707l1.414 1.414a.5.5 0 0 1 0 .708z"/>
</symbol>
</svg>
<div class="dropdown position-fixed bottom-0 end-0 mb-3 me-3 bd-mode-toggle">
<button class="btn btn-bd-secondary py-2 dropdown-toggle d-flex align-items-center"
id="bd-theme"
type="button"
aria-expanded="false"
data-bs-toggle="dropdown"
aria-label="Toggle theme (auto)">
<svg class="bi my-1 theme-icon-active" width="1em" height="1em"><use href="#circle-half"></use></svg>
<span class="visually-hidden" id="bd-theme-text">Toggle theme</span>
</button>
<ul class="dropdown-menu dropdown-menu-end shadow" aria-labelledby="bd-theme-text">
<li>
<button type="button" class="dropdown-item d-flex align-items-center" data-bs-theme-value="light" aria-pressed="false">
<svg class="bi me-2 opacity-50" width="1em" height="1em"><use href="#sun-fill"></use></svg>
Light
<svg class="bi ms-auto d-none" width="1em" height="1em"><use href="#check2"></use></svg>
</button>
</li>
<li>
<button type="button" class="dropdown-item d-flex align-items-center" data-bs-theme-value="dark" aria-pressed="false">
<svg class="bi me-2 opacity-50" width="1em" height="1em"><use href="#moon-stars-fill"></use></svg>
Dark
<svg class="bi ms-auto d-none" width="1em" height="1em"><use href="#check2"></use></svg>
</button>
</li>
<li>
<button type="button" class="dropdown-item d-flex align-items-center active" data-bs-theme-value="auto" aria-pressed="true">
<svg class="bi me-2 opacity-50" width="1em" height="1em"><use href="#circle-half"></use></svg>
Auto
<svg class="bi ms-auto d-none" width="1em" height="1em"><use href="#check2"></use></svg>
</button>
</li>
</ul>
</div>
<svg xmlns="http://www.w3.org/2000/svg" class="d-none">
<symbol id="arrow-right-circle" viewBox="0 0 16 16">
<path d="M8 0a8 8 0 1 1 0 16A8 8 0 0 1 8 0zM4.5 7.5a.5.5 0 0 0 0 1h5.793l-2.147 2.146a.5.5 0 0 0 .708.708l3-3a.5.5 0 0 0 0-.708l-3-3a.5.5 0 1 0-.708.708L10.293 7.5H4.5z"/>
</symbol>
<symbol id="bootstrap" viewBox="0 0 118 94">
<title>Bootstrap</title>
<path fill-rule="evenodd" clip-rule="evenodd" d="M24.509 0c-6.733 0-11.715 5.893-11.492 12.284.214 6.14-.064 14.092-2.066 20.577C8.943 39.365 5.547 43.485 0 44.014v5.972c5.547.529 8.943 4.649 10.951 11.153 2.002 6.485 2.28 14.437 2.066 20.577C12.794 88.106 17.776 94 24.51 94H93.5c6.733 0 11.714-5.893 11.491-12.284-.214-6.14.064-14.092 2.066-20.577 2.009-6.504 5.396-10.624 10.943-11.153v-5.972c-5.547-.529-8.934-4.649-10.943-11.153-2.002-6.484-2.28-14.437-2.066-20.577C105.214 5.894 100.233 0 93.5 0H24.508zM80 57.863C80 66.663 73.436 72 62.543 72H44a2 2 0 01-2-2V24a2 2 0 012-2h18.437c9.083 0 15.044 4.92 15.044 12.474 0 5.302-4.01 10.049-9.119 10.88v.277C75.317 46.394 80 51.21 80 57.863zM60.521 28.34H49.948v14.934h8.905c6.884 0 10.68-2.772 10.68-7.727 0-4.643-3.264-7.207-9.012-7.207zM49.948 49.2v16.458H60.91c7.167 0 10.964-2.876 10.964-8.281 0-5.406-3.903-8.178-11.425-8.178H49.948z"></path>
</symbol>
</svg>
<nav class="navbar navbar-expand-md navbar-dark bg-dark fixed-top">
<div class="container-fluid">
<a class="navbar-brand" href="../"><img class="d-block" id="icon" alt="ImageMagick" width="32" height="32" src="../images/wand.ico"/></a>
<button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#magick-navbars" aria-controls="magick-navbars" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="magick-navbars">
<ul class="navbar-nav me-auto mb-2 mb-md-0">
<li class="nav-item">
<a class="nav-link " href="../www/download.html">Download</a>
</li>
<li class="nav-item">
<a class="nav-link " href="../www/command-line-tools.html">Tools</a>
</li>
<li class="nav-item">
<a class="nav-link " href="../www/command-line-processing.html">CLI</a>
</li>
<li class="nav-item">
<a class="nav-link " href="../www/develop.html">Develop</a>
</li>
<li class="nav-item">
<a class="nav-link" target="_blank" href="https://github.com/ImageMagick/ImageMagick/discussions">Community</a>
</li>
<li class="nav-item">
<iframe src="https://github.com/sponsors/ImageMagick/button" title="Sponsor ImageMagick" height="35" width="107" style="border: 0;"></iframe>
</li>
</ul>
<form class="d-flex form-inline" action="search.html">
<input class="form-control me-2" type="text" name="q" placeholder="Search" aria-label="Search">
<button class="btn btn-outline-success" type="submit" name="sa">Search</button>
</form>
</div>
</div>
</nav>
<div class="col-lg-8 mx-auto p-4 py-md-5 text-body-secondary">
<header class="d-flex align-items-center pb-3 mb-5 border-bottom">
<a href="../" class="d-flex align-items-center text-decoration-none">
<h1 class="fs-4">Convex Hull</h1>
</a>
</header>
<main class="container">
<div>
<p class="text-center"><a href="convex-hull.html#about">Convex Hull</a> • <a href="convex-hull.html#box">Minimum Bounding Box</a> • <a href="convex-hull.html#unrotate">Unrotate an Image</a></p>
<p>The convex hull is the is the smallest area convex polygon containing the set of points inside it. The convex hull may be visualized as the shape enclosed by a rubber band stretched around the set of points.</p>
<p>The convex-hull string format returns a list of x,y coordinates of the vertices of the convex-hull polygon containing all the non-black pixels within it.</p>
<pre class="code">
magick [-fuzz <var>value</var>%] [-background <var>background-color</var>] -format "%[convex-hull]" info:
</pre>
<p>Use <samp>%[convex-hull:extreme-points]</samp> to only return the top, right, bottom, and left extreme points.</p>
<p>where the string format is sensitive to an optional <samp>-fuzz</samp> value and to an optional background color specified by the define. The command above will find the background color automatically according to the fuzz value unless the background color is defined. The fuzz value defaults to 0 when not specified.</p>
<p>For example, consider the following white rectangle on a black background:</p>
<ul><img class="img-fluid border rounded-3 shadow-lg mb-4" src="../images/convex-hull.png" alt="[Convex Hull]" width="250" height="250" name="convert-hull" /></ul>
<p>The convex hull set of points may be computed as:</p>
<pre class="code">magick rect.png -format "%[convex-hull]" info:
190,121 193,122 281,154 377,189 378,190 377,193 345,281 310,377 309,378 306,377 218,345 122,310 121,309 122,306 154,218 189,122 190,121
</pre>
<p>The convex hull may also be drawn as a polygon (filled or unfilled) using <samp>-draw</samp> as follows:</p>
<pre class="code">magick rect.png -set option:hull "%[convex-hull]" -fill none -stroke red -strokewidth 1 -draw "polygon %[hull]" blocks_hull.png</pre>
<p>Here is an example using a non-convex shaped image on a black background:</p>
<ul><img class="img-fluid border rounded-3 shadow-lg mb-4" src="../images/convex-hull-blocks.png" alt="[Convex Hull Blocks]" width="128" height="128" name="convert-hull-blocks" /></ul>
<pre class="code">magick blocks_black.png -set option:hull "%[convex-hull]" -fill none -stroke red -strokewidth 1 -draw "polygon %[hull]" blocks_hull.png</pre>
<ul><img class="img-fluid border rounded-3 shadow-lg mb-4" src="../images/convex-hull-blocks-closure.png" alt="[Convex Hull Blocks Closure]" width="128" height="128" name="convert-hull" /></ul>
<p>Finally, here is an example with a non-constant, non-black background using -fuzz to determine the background color:</p>
<ul><img class="img-fluid border rounded-3 shadow-lg mb-4" src="../images/convex-hull-barn.jpg" alt="[Convex Hull Barn]" width="250" height="250" name="convert-hull-barn" /></ul>
<p>Now let's highlight the convex hull of the image foreground object:</p>
<pre class="code">magick barn_rot20.png -fuzz 10% -set hull "%[convex-hull]" -fill none -stroke red -strokewidth 1 -draw "polygon %[hull]" barn_rot20_hull.png</pre>
<ul><img class="img-fluid border rounded-3 shadow-lg mb-4" src="../images/convex-hull-barn-closure.jpg" alt="[Convex Hull Barn Closure]" width="250" height="250" name="convert-hull-barn-closure" /></ul>
<h2><a class="anchor" id="box"></a>Minimum Bounding Box</h2>
<p>Similar to the convex hull of the image foreground object(s), is the minimum bounding box. Use <samp>%[minimum-bounding-box]</samp> to return the points that make up the bounding box. In addition, these properties are set: <samp>minimum-bounding-box:area</samp>, <samp>minimum-bounding-box:width</samp>, <samp>minimum-bounding-box:height</samp>, and <samp>minimum-bounding-box:angle</samp>.
<pre class="code">magick barn_rot20.png -fuzz 10% -background gray25 -set MBR "%[minimum-bounding-box]" -fill none -stroke red -strokewidth 1 -draw "polygon %[MBR]" barn-mbr.png</pre>
<h2><a class="anchor" id="unrotate"></a>Unrotate an Image</h2>
<p>Use <samp>%[minimum-bounding-box:unrotate]</samp> to correct for any rotation the image may exhibit. Unless you specify the image orientation, the unrotate angle should properly align the image to the correct coordinate axis for angles <= 45. For angles > 45, the image will align with the wrong coordinate axis. Set the correct image orientation to ensure the proper unrotate angle is returned. Use <samp>-define minimum-bounding-box:orientation=<em>{landscape,portrait}</em></samp> to set the image orientation. Note, that like convex-hull, the string format is sensitive to an optional <a href="../www/command-line-options.html#fuzz">-fuzz</a> value and an optional <a href="../www/command-line-options.html#background">-background</a> color.</p>
<p>The barn image above is rotated by 20 degrees. Here is how we can automatically correct for the rotation and return it to its original landscape orientation:
<pre class="code">magick barn_rotate20.jpg -fuzz 15% -set option:angle "%[minimum-bounding-box:unrotate]" -background gray -rotate "%[angle]" -trim barn_unrotate.jpg</pre>
</p>
</div>
</div>
</main><!-- /.container -->
<footer class="py-5 text-center text-body-secondary bg-body-tertiary">
<div class="container-fluid">
<a href="../www/security-policy.html">Security</a> •
<a href="../www/news.html">News</a>
<a href="convex-hull.html#"><img class="d-inline" id="wand" alt="And Now a Touch of Magick" width="16" height="16" src="../images/wand.ico"/></a>
<a href="../www/links.html">Related</a> •
<a href="../www/sitemap.html">Sitemap</a>
<br/>
<a href="../www/support.html">Sponsor</a> •
<a href="../www/cite.html">Cite</a> •
<a href="http://pgp.mit.edu/pks/lookup?op=get&search=0x89AB63D48277377A">Public Key</a> •
<a href="../www/https://imagemagick.org/script/contact.php">Contact Us</a>
<br/>
<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> •
<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 0 300 300" width="2%" height="2%" role="img" focusable="false"><title>Twitter</title><path d="M178.57 127.15 290.27 0h-26.46l-97.03 110.38L89.34 0H0l117.13 166.93L0 300.25h26.46l102.4-116.59 81.8 116.59h89.34M36.01 19.54H76.66l187.13 262.13h-40.66"/></svg></a>
<br/>
<small>Copyright © 1999 ImageMagick Studio LLC</small>
</div>
</footer>
</div>
<!-- Javascript assets -->
<script src="assets/magick.js" ></script>
</body>
</html>
<!-- Magick Cache 19th April 2024 10:40 -->