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<p class="navigation-index">[<a href="#anatomy">The Anatomy of the Command Line</a> • <a href="#input">Input Filename</a> • <a href="#setting">Image Setting</a> • <a href="#operator">Image Operator</a> • <a href="#sequence">Image Sequence Operator</a> • <a href="#geometry">Image Geometry</a> • <a href="#stack">Image Stack</a> • <a href="#output">Output Filename</a>]</p>
<p>The ImageMagick command line can be as simple as </p>
<div class="cmd">
convert image.jpg image.png
</div>
<p>or very complex, as in the following.</p>
<div class="cmd">
convert label.gif +matte <br/>
\( +clone -shade 110x90 -normalize -negate +clone -compose Plus -composite \) <br/>
\( -clone 0 -shade 110x50 -normalize -channel BG -fx 0 +channel -matte \) <br/>
-delete 0 +swap -compose Multiply -composite button.gif
</div> <!-- end cmd -->
<p style="padding-left: 3%; padding-right: 3%; background: #FFEEDD">[<em>A quick word about our formatting of commands:</em> The example above is long enough that the command must be written across several lines, but it is still typed as one line. In the Windows shell, a carat character (<kbd>^</kbd>) may be used as a <em>line continuation</em> character, while in Unix-like systems, a backslash (<kbd>\</kbd>) may be used. We will not show those continuation characters—unless otherwise noted, all commands should be entered on a single line. The parentheses that are <em>escaped</em> above using the backslash are not escaped in Windows. There are some other differences between Windows and Unix (involving quotation marks, for instance), but we'll forego those discussions for now.]</p>
<p>Without knowing much about the ImageMagick command line, you can probably figure out that the first command above converts an image in the JPEG format to one in the PNG format. However, very few may realize the second, more complex command, gives a flat two-dimensional label a three-dimensional look with rich textures and simulated depth:</p>
<div class="image">
<p>
<a href="../images/label.gif"><img src="../images/label.gif" width="78" height="53" alt="label" /></a>
<img style="margin:16px 0;" src="../images/right.gif" width="20" height="20" alt="==>" />
<a href="../images/button.gif">
<img src="../images/button.gif" width="78" height="53" alt="button" /></a>
</p>
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<p>In the next sections we dissect the anatomy of the ImageMagick command line. Hopefully, after carefully reading and better understanding how the command line works, you should be able to accomplish complex image-processing tasks without resorting to the sometimes daunting <a href="../www/api.html">program interfaces</a>.</p>
<p>See <a href="http://www.imagemagick.org/Usage/">Examples of ImageMagick Usage</a> for additional help when using ImageMagick from the command-line.</p>
<div style="margin: auto;">
<h2><a name="anatomy"></a>The Anatomy of the Command Line</h2>
</div>
<p>The ImageMagick command line consists of</p>
<ol>
<li>one or more required input filenames.</li>
<li>zero, one, or more image settings.</li>
<li>zero, one, or more image operators.</li>
<li>zero, one, or more image sequence operators.</li>
<li>zero, one, or more image stacks.</li>
<li>zero or one output image filenames (required by <a href="../www/convert.html">convert</a>, <a href="../www/composite.html">composite</a>, <a href="../www/montage.html">montage</a>, <a href="../www/compare.html">compare</a>, <a href="../www/import.html">import</a>, and <a href="../www/conjure.html">conjure</a>).</li>
</ol>
<p>You can find a detailed explanation of each of the constituent parts of the command line in the sections that follow.</p>
<div style="margin: auto;">
<h2><a name="input"></a>Input Filename</h2>
</div>
<p>ImageMagick extends the concept of an input filename to include: 1) filename globbing; 2) an explicit image format; 3) using built-in images and patterns; 4) reading an image from <em>standard in</em>; 5) selecting certain frames from an image; and 6) selecting a region of an image. Each of these extensions are explained in the next few paragraphs.</p>
<dl class="doc">
<dt class="doc">Filename Globbing</dt>
<dd>In Unix shells, certain characters such as the asterisk (<kbd>*</kbd>) and question mark (<kbd>?</kbd>) automatically cause lists of filenames to be generated based on pattern matches. This feature is known as globbing. ImageMagick supports filename globbing for systems, such as Windows, that does not natively support it. For example, suppose you want to convert <kbd>1.jpg</kbd>, <kbd>2.jpg</kbd>, <kbd>3.jpg</kbd>, <kbd>4.jpg</kbd>, and <kbd>5.jpg</kbd> in your current directory to a GIF animation. You can conveniently refer to all of the JPEG files with this command:
<div class="cmd">
convert *.jpg images.gif
</div> <!-- end cmd -->
</dd>
<dt class="doc">Explicit Image Format</dt>
<dd>Images are stored in a mryiad of image formats including the better known JPEG, PNG, TIFF and others. ImageMagick must know the format of the image before it can be read and processed. Most formats have a signature within the image that uniquely identifies the format. Failing that, ImageMagick leverages the filename extension to determine the format. For example, <kbd>image.jpg</kbd> tells ImageMagick it is reading an image in the JPEG format. In some cases the image may not contain a signature and/or the filename does not identify the image format. In these cases an explicit image format must be specified. For example, suppose our image is named <kbd>image</kbd> and contains raw red, green, and blue intensity values. ImageMagick has no way to automagically determine the image format so we explicitly set one:
<div class="cmd">
convert -size 640x480 -depth 8 rgb:image image.png
</div> <!-- end cmd -->
</dd>
<dt class="doc">Built-in Images and Patterns</dt>
<dd>ImageMagick has a number of built-in <a href="../www/formats.html#builtin-images">images</a> and <a href="../www/formats.html#builtin-patterns">patterns</a>. To utilize the checkerboard pattern, for example, use:
<div class="cmd">
convert -size 640x480 pattern:checkerboard checkerboard.png
</div> <!-- end cmd -->
</dd>
<dt class="doc">Standard In</dt>
<dd>Unix permits the output of one command to be piped to another. ImageMagick permits piping one command to another with a filename of <kbd>-</kbd>. In this example we pipe the output of <kbd>convert</kbd> to the <kbd>display</kbd> program:
<div class="cmd">
convert logo: gif:- • display gif:-
</div> <!-- end cmd -->
Here the explicit format is optional. The GIF image format has a unique signature within the image so ImageMagick can readily recognize the format as GIF.
</dd>
<dt class="doc">Selecting Frames</dt>
<dd>Some images formats contain more than one image frame. Perhaps you only want the first image, or the last, or some number of images in-between. You can specify which image frames to read by appending the image filename with the frame range enclosed in brackets. Here our image contains more than one frame but we only want the first:
<div class="cmd">
convert images.gif[0] image.png
</div> <!-- end cmd -->
Unix shells generally interpret brackets so we must enclose the filename in quotes:
<div class="cmd">
convert 'images.gif[0]' image.png
</div> <!-- end cmd -->
You can read more than one image from a sequence with a frame range. For example, suppose you want the first four frames of an image sequence:
<div class="cmd">
convert 'images.gif[0-4]' images.mng
</div> <!-- end cmd -->
Finally, you can read more than one image from a sequence, out-of-order. This reads the third image in the sequence, followed by the second, and then the fourth:
<div class="cmd">
convert 'images.gif[3,2,4]' images.mng
</div> <!-- end cmd -->
</dd>
<dt class="doc">Selecting an Image Region</dt>
<dd>Raw images are a sequence of color intensities without additional meta information such as width, height, or image signature. With raw image formats, you must specify the image width and height but you can also specify a region of the image to read. In our example, the image is in the raw 8-bit RGB format and is 6000 pixels wide and 4000 pixels high. However, we only want a region of 600 by 400 near the center of the image:
<div class="cmd">
convert -size 6000x4000 -depth 8 'rgb:image[600x400+1900+2900]' image.jpg
</div> <!-- end cmd -->
You can get the same results with the <a href="../www/command-line-options.html#extract">-extract</a> option:
<div class="cmd">
convert -size 6000x4000 -depth 8 -extract 600x400+1900+2900 rgb:image image.jpg
</div> <!-- end cmd -->
</dd>
<dt class="doc">Inline Image Resize</dt>
<dd>It is sometimes convenient to resize an image as they are read. Suppose you have hundreds of large JPEG images you want to convert to a sequence of PNG thumbails:
<div class="cmd">
convert '*.jpg' -resize 120x120 thumbnail%03d.png
</div> <!-- end cmd -->
Here <em>all</em> the images are read and subsequently resized. It is faster and less resource intensive to resize each image as they are read:
<div class="cmd">
convert '*.jpg[120x120]' thumbnail%03d.png
</div> <!-- end cmd -->
</dd>
<dt class="doc">Inline Image Crop</dt>
<dd>It is sometimes convenient to crop an image as they are read. Suppose you have hundreds of large JPEG images you want to convert to a sequence of PNG thumbails:
<div class="cmd">
convert '*.jpg' -crop 120x120+10+5 thumbnail%03d.png
</div> <!-- end cmd -->
Here <em>all</em> the images are read and subsequently cropped. It is faster and less resource intensive to crop each image as they are read:
<div class="cmd">
convert '*.jpg[120x120+10+5]' thumbnail%03d.png
</div> <!-- end cmd -->
</dd>
<dt class="doc">Filename References</dt>
<dd>There are two methods to use a filename to reference other image filenames.
The first is with '<kbd>@</kbd>' which reads image filenames from the specified file. Assume <kbd>myimages.txt</kbd> contains these lines:
<pre class="code">
image-1.jpg
image-2.jpg
image-3.jpg
</pre>
Here, ImageMagick reads <kbd>image-1.jpg</kbd>, <kbd>image-2.jpg</kbd>, and <kbd>image-3.jpg</kbd>. Another method of referring to other image files is by an embedding a formatting character in the filename with a scene range. Consider the filename <kbd>image-%d.jpg[1-5]</kbd>. ImageMagick attempts to read images from these filenames:
<pre class="code">
image-1.jpg
image-2.jpg
image-3.jpg
image-4.jpg
image-5.jpg
</pre>
</dd>
</dl>
<div style="margin: auto;">
<h2><a name="setting"></a>Image Setting</h2>
</div>
<p>An image setting persists as it appears on the command line and may affect subsequent processing such as reading an image, an image operator, or when writing an image as appropriate. An image setting stays in effect until it is reset or the command line terminates. The image settings include:</p>
<p class="options">
<span class='bull'> • </span>
<a href="../www/command-line-options.html#adjoin">‑adjoin</a> <span class='bull'> • </span><a href="../www/command-line-options.html#affine">‑affine</a> <span class='bull'> • </span><a href="../www/command-line-options.html#alpha">‑alpha</a> <span class='bull'> • </span><a href="../www/command-line-options.html#antialias">‑antialias</a> <span class='bull'> • </span><a href="../www/command-line-options.html#authenticate">‑authenticate</a> <span class='bull'> • </span><a href="../www/command-line-options.html#background">‑background</a> <span class='bull'> • </span><a href="../www/command-line-options.html#bias">‑bias</a> <span class='bull'> • </span><a href="../www/command-line-options.html#black-point-compensation">‑black‑point‑compensation</a> <span class='bull'> • </span><a href="../www/command-line-options.html#blue-primary">‑blue‑primary</a> <span class='bull'> • </span><a href="../www/command-line-options.html#bordercolor">‑bordercolor</a> <span class='bull'> • </span><a href="../www/command-line-options.html#caption">‑caption</a> <span class='bull'> • </span><a href="../www/command-line-options.html#channel">‑channel</a> <span class='bull'> • </span><a href="../www/command-line-options.html#comment">‑comment</a> <span class='bull'> • </span><a href="../www/command-line-options.html#compress">‑compress</a> <span class='bull'> • </span><a href="../www/command-line-options.html#debug">‑debug</a> <span class='bull'> • </span><a href="../www/command-line-options.html#define">‑define</a> <span class='bull'> • </span><a href="../www/command-line-options.html#delay">‑delay</a> <span class='bull'> • </span><a href="../www/command-line-options.html#density">‑density</a> <span class='bull'> • </span><a href="../www/command-line-options.html#depth">‑depth</a> <span class='bull'> • </span><a href="../www/command-line-options.html#display">‑display</a> <span class='bull'> • </span><a href="../www/command-line-options.html#dispose">‑dispose</a> <span class='bull'> • </span><a href="../www/command-line-options.html#dither">‑dither</a> <span class='bull'> • </span><a href="../www/command-line-options.html#encoding">‑encoding</a> <span class='bull'> • </span><a href="../www/command-line-options.html#endian">‑endian</a> <span class='bull'> • </span><a href="../www/command-line-options.html#extract">‑extract</a> <span class='bull'> • </span><a href="../www/command-line-options.html#family">‑family</a> <span class='bull'> • </span><a href="../www/command-line-options.html#fill">‑fill</a> <span class='bull'> • </span><a href="../www/command-line-options.html#filter">‑filter</a> <span class='bull'> • </span><a href="../www/command-line-options.html#font">‑font</a> <span class='bull'> • </span><a href="../www/command-line-options.html#format">‑format</a> <span class='bull'> • </span><a href="../www/command-line-options.html#fuzz">‑fuzz</a> <span class='bull'> • </span><a href="../www/command-line-options.html#geometry">‑geometry</a> <span class='bull'> • </span><a href="../www/command-line-options.html#gravity">‑gravity</a> <span class='bull'> • </span><a href="../www/command-line-options.html#green-primary">‑green‑primary</a> <span class='bull'> • </span><a href="../www/command-line-options.html#interlace">‑interlace</a> <span class='bull'> • </span><a href="../www/command-line-options.html#intent">‑intent</a> <span class='bull'> • </span><a href="../www/command-line-options.html#interpolate">‑interpolate</a> <span class='bull'> • </span><a href="../www/command-line-options.html#label">‑label</a> <span class='bull'> • </span><a href="../www/command-line-options.html#limit">‑limit</a> <span class='bull'> • </span><a href="../www/command-line-options.html#linewidth">‑linewidth</a> <span class='bull'> • </span><a href="../www/command-line-options.html#log">‑log</a> <span class='bull'> • </span><a href="../www/command-line-options.html#loop">‑loop</a> <span class='bull'> • </span><a href="../www/command-line-options.html#mask">‑mask</a> <span class='bull'> • </span><a href="../www/command-line-options.html#mattecolor">‑mattecolor</a> <span class='bull'> • </span><a href="../www/command-line-options.html#monitor">‑monitor</a> <span class='bull'> • </span><a href="../www/command-line-options.html#orient">‑orient</a> <span class='bull'> • </span><a href="../www/command-line-options.html#page">‑page</a> <span class='bull'> • </span><a href="../www/command-line-options.html#pointsize">‑pointsize</a> <span class='bull'> • </span><a href="../www/command-line-options.html#preview">‑preview</a> <span class='bull'> • </span><a href="../www/command-line-options.html#quality">‑quality</a> <span class='bull'> • </span><a href="../www/command-line-options.html#quiet">‑quiet</a> <span class='bull'> • </span><a href="../www/command-line-options.html#red-primary">‑red‑primary</a> <span class='bull'> • </span><a href="../www/command-line-options.html#region">‑region</a> <span class='bull'> • </span><a href="../www/command-line-options.html#render">‑render</a> <span class='bull'> • </span><a href="../www/command-line-options.html#repage">‑repage</a> <span class='bull'> • </span><a href="../www/command-line-options.html#sampling-factor">‑sampling‑factor</a> <span class='bull'> • </span><a href="../www/command-line-options.html#scene">‑scene</a> <span class='bull'> • </span><a href="../www/command-line-options.html#seed">‑seed</a> <span class='bull'> • </span><a href="../www/command-line-options.html#size">‑size</a> <span class='bull'> • </span><a href="../www/command-line-options.html#stretch">‑stretch</a> <span class='bull'> • </span><a href="../www/command-line-options.html#stroke">‑stroke</a> <span class='bull'> • </span><a href="../www/command-line-options.html#strokewidth">‑strokewidth</a> <span class='bull'> • </span><a href="../www/command-line-options.html#style">‑style</a> <span class='bull'> • </span><a href="../www/command-line-options.html#texture">‑texture</a> <span class='bull'> • </span><a href="../www/command-line-options.html#tile">‑tile</a> <span class='bull'> • </span><a href="../www/command-line-options.html#transparent-color">‑transparent‑color</a> <span class='bull'> • </span><a href="../www/command-line-options.html#treedepth">‑treedepth</a> <span class='bull'> • </span><a href="../www/command-line-options.html#type">‑type</a> <span class='bull'> • </span><a href="../www/command-line-options.html#undercolor">‑undercolor</a> <span class='bull'> • </span><a href="../www/command-line-options.html#units">‑units</a> <span class='bull'> • </span><a href="../www/command-line-options.html#verbose">‑verbose</a> <span class='bull'> • </span><a href="../www/command-line-options.html#virtual-pixel">‑virtual‑pixel</a> <span class='bull'> • </span><a href="../www/command-line-options.html#weight">‑weight</a> <span class='bull'> • </span>
</p>
<p>In this example, <em class="arg">-channel</em> applies to each of the images, since, as we mentioned, settings persist:</p>
<div class="cmd">
convert -channel RGB wand.png wizard.png images.png
</div> <!-- end cmd -->
<div style="margin: auto;">
<h2><a name="operator"></a>Image Operator</h2>
</div>
<p>An image operator differs from a setting in that it affects the image immediately as it appears on the command line. An operator is any <a href="../www/command-line-options.html">command line option</a> not listed as a <a href="#setting">image setting</a> or <a href="#sequence">image sequence operator</a>. Unlike an image setting, which persists until the command line terminates, an operator is applied to an image and forgotten. The image operators include:</p>
<p class="options">
<span class='bull'> • </span>
<a href="../www/command-line-options.html#annotate">‑annotate</a> <span class='bull'> • </span><a href="../www/command-line-options.html#black-threshold">‑black‑threshold</a> <span class='bull'> • </span><a href="../www/command-line-options.html#blur">‑blur</a> <span class='bull'> • </span><a href="../www/command-line-options.html#border">‑border</a> <span class='bull'> • </span><a href="../www/command-line-options.html#charcoal">‑charcoal</a> <span class='bull'> • </span><a href="../www/command-line-options.html#chop">‑chop</a> <span class='bull'> • </span><a href="../www/command-line-options.html#clip">‑clip</a> <span class='bull'> • </span><a href="../www/command-line-options.html#clip-path">‑clip‑path</a> <span class='bull'> • </span><a href="../www/command-line-options.html#clip-mask">‑clip‑mask</a> <span class='bull'> • </span><a href="../www/command-line-options.html#colors">‑colors</a> <span class='bull'> • </span><a href="../www/command-line-options.html#colorize">‑colorize</a> <span class='bull'> • </span><a href="../www/command-line-options.html#colorspace">‑colorspace</a> <span class='bull'> • </span><a href="../www/command-line-options.html#compose">‑compose</a> <span class='bull'> • </span><a href="../www/command-line-options.html#contrast">‑contrast</a> <span class='bull'> • </span><a href="../www/command-line-options.html#convolve">‑convolve</a> <span class='bull'> • </span><a href="../www/command-line-options.html#crop">‑crop</a> <span class='bull'> • </span><a href="../www/command-line-options.html#cycle">‑cycle</a> <span class='bull'> • </span><a href="../www/command-line-options.html#despeckle">‑despeckle</a> <span class='bull'> • </span><a href="../www/command-line-options.html#draw">‑draw</a> <span class='bull'> • </span><a href="../www/command-line-options.html#edge">‑edge</a> <span class='bull'> • </span><a href="../www/command-line-options.html#emboss">‑emboss</a> <span class='bull'> • </span><a href="../www/command-line-options.html#enhance">‑enhance</a> <span class='bull'> • </span><a href="../www/command-line-options.html#equalize">‑equalize</a> <span class='bull'> • </span><a href="../www/command-line-options.html#evaluate">‑evaluate</a> <span class='bull'> • </span><a href="../www/command-line-options.html#extent">‑extent</a> <span class='bull'> • </span><a href="../www/command-line-options.html#flip">‑flip</a> <span class='bull'> • </span><a href="../www/command-line-options.html#flop">‑flop</a> <span class='bull'> • </span><a href="../www/command-line-options.html#floodfill">‑floodfill</a> <span class='bull'> • </span><a href="../www/command-line-options.html#frame">‑frame</a> <span class='bull'> • </span><a href="../www/command-line-options.html#gamma">‑gamma</a> <span class='bull'> • </span><a href="../www/command-line-options.html#gaussian-blur">‑gaussian‑blur</a> <span class='bull'> • </span><a href="../www/command-line-options.html#implode">‑implode</a> <span class='bull'> • </span><a href="../www/command-line-options.html#lat">‑lat</a> <span class='bull'> • </span><a href="../www/command-line-options.html#level">‑level</a> <span class='bull'> • </span><a href="../www/command-line-options.html#map">‑map</a> <span class='bull'> • </span><a href="../www/command-line-options.html#mask">‑mask</a> <span class='bull'> • </span><a href="../www/command-line-options.html#median">‑median</a> <span class='bull'> • </span><a href="../www/command-line-options.html#modulate">‑modulate</a> <span class='bull'> • </span><a href="../www/command-line-options.html#monochrome">‑monochrome</a> <span class='bull'> • </span><a href="../www/command-line-options.html#negate">‑negate</a> <span class='bull'> • </span><a href="../www/command-line-options.html#noise">‑noise</a> <span class='bull'> • </span><a href="../www/command-line-options.html#normalize">‑normalize</a> <span class='bull'> • </span><a href="../www/command-line-options.html#opaque">‑opaque</a> <span class='bull'> • </span><a href="../www/command-line-options.html#ordered-dither">‑ordered‑dither</a> <span class='bull'> • </span><a href="../www/command-line-options.html#paint">‑paint</a> <span class='bull'> • </span><a href="../www/command-line-options.html#posterize">‑posterize</a> <span class='bull'> • </span><a href="../www/command-line-options.html#raise">‑raise</a> <span class='bull'> • </span><a href="../www/command-line-options.html#profile">‑profile</a> <span class='bull'> • </span><a href="../www/command-line-options.html#radial-blur">‑radial‑blur</a> <span class='bull'> • </span><a href="../www/command-line-options.html#raise">‑raise</a> <span class='bull'> • </span><a href="../www/command-line-options.html#random-threshold">‑random‑threshold</a> <span class='bull'> • </span><a href="../www/command-line-options.html#resample">‑resample</a> <span class='bull'> • </span><a href="../www/command-line-options.html#resize">‑resize</a> <span class='bull'> • </span><a href="../www/command-line-options.html#roll">‑roll</a> <span class='bull'> • </span><a href="../www/command-line-options.html#rotate">‑rotate</a> <span class='bull'> • </span><a href="../www/command-line-options.html#sample">‑sample</a> <span class='bull'> • </span><a href="../www/command-line-options.html#scale">‑scale</a> <span class='bull'> • </span><a href="../www/command-line-options.html#sepia-tone">‑sepia‑tone</a> <span class='bull'> • </span><a href="../www/command-line-options.html#segment">‑segment</a> <span class='bull'> • </span><a href="../www/command-line-options.html#shade">‑shade</a> <span class='bull'> • </span><a href="../www/command-line-options.html#shadow">‑shadow</a> <span class='bull'> • </span><a href="../www/command-line-options.html#sharpen">‑sharpen</a> <span class='bull'> • </span><a href="../www/command-line-options.html#shave">‑shave</a> <span class='bull'> • </span><a href="../www/command-line-options.html#shear">‑shear</a> <span class='bull'> • </span><a href="../www/command-line-options.html#sigmoidal-contrast">‑sigmoidal‑contrast</a> <span class='bull'> • </span><a href="../www/command-line-options.html#solarize">‑solarize</a> <span class='bull'> • </span><a href="../www/command-line-options.html#splice">‑splice</a> <span class='bull'> • </span><a href="../www/command-line-options.html#spread">‑spread</a> <span class='bull'> • </span><a href="../www/command-line-options.html#strip">‑strip</a> <span class='bull'> • </span><a href="../www/command-line-options.html#swirl">‑swirl</a> <span class='bull'> • </span><a href="../www/command-line-options.html#threshold">‑threshold</a> <span class='bull'> • </span><a href="../www/command-line-options.html#transparent">‑transparent</a> <span class='bull'> • </span><a href="../www/command-line-options.html#thumbnail">‑thumbnail</a> <span class='bull'> • </span><a href="../www/command-line-options.html#tint">‑tint</a> <span class='bull'> • </span><a href="../www/command-line-options.html#transform">‑transform</a> <span class='bull'> • </span><a href="../www/command-line-options.html#trim">‑trim</a> <span class='bull'> • </span><a href="../www/command-line-options.html#unsharp">‑unsharp</a> <span class='bull'> • </span><a href="../www/command-line-options.html#version">‑version</a> <span class='bull'> • </span><a href="../www/command-line-options.html#wave">‑wave</a> <span class='bull'> • </span><a href="../www/command-line-options.html#white-point">‑white‑point</a> <span class='bull'> • </span><a href="../www/command-line-options.html#white-threshold">‑white‑threshold</a> <span class='bull'> • </span>
</p>
<p>In this example, <em class="arg">-negate</em> negates the wand image but not the wizard:</p>
<div class="cmd">
convert wand.png -negate wizard.png images.png
</div> <!-- end cmd -->
<div style="margin: auto;">
<h2><a name="sequence"></a>Image Sequence Operator</h2>
</div>
<p>An image sequence operator differs from a setting in that it affects an image sequence immediately as it appears on the command line. Choose from these image sequence operators:</p>
<p class="options">
<span class='bull'> • </span>
<a href="../www/command-line-options.html#append">‑append</a> <span class='bull'> • </span><a href="../www/command-line-options.html#average">‑average</a> <span class='bull'> • </span><a href="../www/command-line-options.html#clut">‑clut</a> <span class='bull'> • </span><a href="../www/command-line-options.html#coalesce">‑coalesce</a> <span class='bull'> • </span><a href="../www/command-line-options.html#combine">‑combine</a> <span class='bull'> • </span><a href="../www/command-line-options.html#composite">‑composite</a> <span class='bull'> • </span><a href="../www/command-line-options.html#crop">‑crop</a> <span class='bull'> • </span><a href="../www/command-line-options.html#deconstruct">‑deconstruct</a> <span class='bull'> • </span><a href="../www/command-line-options.html#delete">‑delete</a> <span class='bull'> • </span><a href="../www/command-line-options.html#flatten">‑flatten</a> <span class='bull'> • </span><a href="../www/command-line-options.html#fx">‑fx</a> <span class='bull'> • </span><a href="../www/command-line-options.html#identify">‑identify</a> <span class='bull'> • </span><a href="../www/command-line-options.html#insert">‑insert</a> <span class='bull'> • </span><a href="../www/command-line-options.html#map">‑map</a> <span class='bull'> • </span><a href="../www/command-line-options.html#morph">‑morph</a> <span class='bull'> • </span><a href="../www/command-line-options.html#mosaic">‑mosaic</a> <span class='bull'> • </span><a href="../www/command-line-options.html#process">‑process</a> <span class='bull'> • </span><a href="../www/command-line-options.html#reverse">‑reverse</a> <span class='bull'> • </span><a href="../www/command-line-options.html#separate">‑separate</a> <span class='bull'> • </span><a href="../www/command-line-options.html#swap">‑swap</a> <span class='bull'> • </span><a href="../www/command-line-options.html#write">‑write</a> <span class='bull'> • </span>
</p>
<div style="margin: auto;">
<h2><a name="geometry"></a>Image Geometry</h2>
</div>
<p>Many command-line options take a <em class="arg">geometry</em> argument to specify such things as the desired width and height of an image and other dimensional quantities. Because users want so many variations on the resulting dimensions, sizes, and positions of images (and because ImageMagick wants to provide them), the <em class="arg">geometry</em> argument can take many forms. We describe many of these in this section. </p>
<p>The image options and settings that take some form of a <em class="arg">geometry</em> argument include the following. Keep in mind that some of these parse their arguments in slightly different ways. See the documentation for the individual option or setting for more specifics.</p>
<p class="options">
<span class='bull'> • </span>
<a href="../www/command-line-options.html#adaptive-resize">‑adaptive‑resize</a> <span class='bull'> • </span><a href="../www/command-line-options.html#border">‑border</a> <span class='bull'> • </span><a href="../www/command-line-options.html#borderwidth">‑borderwidth</a> <span class='bull'> • </span><a href="../www/command-line-options.html#chop">‑chop</a> <span class='bull'> • </span><a href="../www/command-line-options.html#crop">‑crop</a> <span class='bull'> • </span><a href="../www/command-line-options.html#density">‑density</a> <span class='bull'> • </span><a href="../www/command-line-options.html#extent">‑extent</a> <span class='bull'> • </span><a href="../www/command-line-options.html#extract">‑extract</a> <span class='bull'> • </span><a href="../www/command-line-options.html#frame">‑frame</a> <span class='bull'> • </span><a href="../www/command-line-options.html#geometry">‑geometry</a> <span class='bull'> • </span><a href="../www/command-line-options.html#iconGeometry">‑iconGeometry</a> <span class='bull'> • </span><a href="../www/command-line-options.html#liquid-rescale">‑liquid‑rescale</a> <span class='bull'> • </span><a href="../www/command-line-options.html#page">‑page</a> <span class='bull'> • </span><a href="../www/command-line-options.html#region">‑region</a> <span class='bull'> • </span><a href="../www/command-line-options.html#repage">‑repage</a> <span class='bull'> • </span><a href="../www/command-line-options.html#resize">‑resize</a> <span class='bull'> • </span><a href="../www/command-line-options.html#sample">‑sample</a> <span class='bull'> • </span><a href="../www/command-line-options.html#scale">‑scale</a> <span class='bull'> • </span><a href="../www/command-line-options.html#shave">‑shave</a> <span class='bull'> • </span><a href="../www/command-line-options.html#splice">‑splice</a> <span class='bull'> • </span><a href="../www/command-line-options.html#extent">‑extent</a> <span class='bull'> • </span><a href="../www/command-line-options.html#thumbnail">‑thumbnail</a> <span class='bull'> • </span><a href="../www/command-line-options.html#window">‑window</a> <span class='bull'> • </span>
</p>
<p>The <em class="arg">geometry</em> argument might take any of the forms listed in the table below. These will described in more detail in the subsections following the table. The usual form is <em class="arg">size</em>[<em class="arg">offset</em>], meaning <em class="arg">size</em> is required and <em class="arg">offset</em> is optional. Occasionally, [<em class="arg">size</em>]<em class="arg">offset</em> is possible. In no cases are spaces permitted within the <em class="arg">geometry</em> argument.</p>
<table id="geometryTable" class="doc">
<col width="20%"/> <col width="80%"/>
<thead>
<tr valign="top">
<th style="text-align:center"><em class="arg">size</em></th>
<th>General description (actual behavior can vary for different options and settings)</th>
</tr>
</thead>
<tbody>
<tr valign="top">
<td><em class="arg">scale</em>%</td>
<td>Height and width both scaled by specified percentage.</td>
</tr>
<tr valign="top">
<td><em class="arg">scale-x</em>%x<em class="arg">scale-y</em>%</td>
<td>Height and width individually scaled by specified percentages. (Only one % symbol needed.)</td>
</tr>
<tr valign="top">
<td><em class="arg">width</em></td>
<td>Width given, height automatically selected to preserve aspect ratio.</td>
</tr>
<tr valign="top">
<td>x<em class="arg">height</em></td>
<td>Height given, width automatically selected to preserve aspect ratio.</td>
</tr>
<tr valign="top">
<td><em class="arg">width</em>x<em class="arg">height</em></td>
<td>Maximum values of height and width given, aspect ratio preserved.</td>
</tr>
<tr valign="top">
<td><em class="arg">width</em>x<em class="arg">height</em>^</td>
<td>Minimum values of width and height given, aspect ratio preserved.</td>
</tr>
<tr valign="top">
<td><em class="arg">width</em>x<em class="arg">height</em>!</td>
<td>Width and height emphatically given, original aspect ratio ignored.</td>
</tr>
<tr valign="top">
<td><em class="arg">width</em>x<em class="arg">height</em>></td>
<td>Change as per <em class="arg">width</em>x<em class="arg">height</em> but only if an image dimension is exceeded by a specified dimension.</td>
</tr>
<tr valign="top">
<td><em class="arg">width</em>x<em class="arg">height</em><</td>
<td>Change dimensions only if both specified dimensions exceed image dimensions.</td>
</tr>
<tr valign="top">
<td><em class="arg">area</em>@</td>
<td>Resize image to have specified area in pixels. Aspect ratio is preserved.</td>
</tr>
</tbody>
</table>
<table class="doc">
<col width="20%"/> <col width="80%"/>
<thead>
<tr valign="top">
<th style="text-align:center">{<em class="arg">size</em>}{<em class="arg">offset</em>}</th>
<th>Specifying the <em class="arg">offset</em> (default is <kbd>+0+0</kbd>). Below, {<em class="arg">size</em>} refers to any of the forms above.</th>
</tr>
</thead>
<tbody>
<tr valign="top">
<td>{<em class="arg">size</em>}{<em class="arg">+-</em>}<em class="arg">x</em>{<em class="arg">+-</em>}<em class="arg">y</em></td>
<td>Horizontal and vertical offsets <em class="arg">x</em> and <em class="arg">y</em>, specified in pixels. Signs are required for both. Offsets are affected by <a href="../www/command-line-options.html#gravity">‑gravity</a> setting. Offsets are not affected by <kbd>%</kbd> or other <em class="arg">size</em> operators.</td>
</tr>
</tbody>
</table>
<dl class="doc">
<dt class="doc"> Basic adjustments to width and height; the operators <kbd>%</kbd>, <kbd>^</kbd>, and <kbd>!</kbd> </dt>
<dd>
<p>Here, just below, are a few simple examples of <em class="arg">geometry</em>, showing how it might be used as an argument to the <a href="../www/command-line-options.html#resize">‑resize</a> option. We'll use the internal image <kbd>logo:</kbd> for our input image.
<a href="../images/logo-fullsize.png">
This fine image</a> is 640 pixels wide and 480 pixels high. We say its <em>dimensions</em> are 640x480. When we give dimensions of an image, the width (the horizontal dimension) always precedes the height (the vertical dimension). This will be true when we speak of coordinates or <em>offsets</em> into an image, which will always be <em>x</em>–value followed by <em>y</em>. Just think of your high school algebra classes and the <em>xy</em>–plane. (Well, almost: our <em>y</em>–axis will always go downward!)
</p>
<div class="cmd">
convert logo: -resize "200%" bigWiz.png
</div> <!-- end cmd -->
<div class="cmd">
convert logo: -resize "200x50%" longShortWiz.png
</div> <!-- end cmd -->
<div class="cmd">
convert logo: -resize "100x200" notThinWiz.png
</div> <!-- end cmd -->
<div class="cmd">
convert logo: -resize "100x200^" biggerNotThinWiz.png
</div> <!-- end cmd -->
<div class="cmd">
convert logo: -resize "100x200!" dochThinWiz.png
</div> <!-- end cmd -->
<p>The first of the four commands is simple—it stretches both the width and height of the input image by <kbd>200%</kbd> in each direction; it magnifies the whole thing by a factor of two. The second command specifies different percentages for each direction, stretching the width to <kbd>200</kbd>% and squashing the height to <kbd>50%</kbd>. The resulting image (in this example) has dimensions 1280x240. Notice that the percent symbol needn't be repeated; the following are equivalent: <kbd>200x50%</kbd>, <kbd>200%x50</kbd>, <kbd>200%x50%</kbd>.
</p>
<p>By default, the width and height given in a <em class="arg">geometry</em> argument are <em>maximum</em> values unless a percentage is specified. That is, the image is expanded or contracted to fit the specified width and height value while maintaining the <em>aspect ratio</em> (the ratio of its height to its width) of the image. For instance, the third command above "tries" to set the dimensions to <kbd>100x200</kbd>. Imagine gradually shrinking the original image (which is 640x480), keeping is aspect ratio constant, until it just fits into a 100x200 rectangle. Since the image is longer than it is tall, it will fit when its width shrinks to 100 pixels. To preserve the aspect ratio, the height will therefore have to be (480/640)×100 pixels=75 pixels, so the final dimensions will be 100x75.</p>
<p> Notice that in the previous example, at least one of the specified dimensions will be attained (in this case, the width, 100 pixels). The resulting image fits snugly within the original. One can do just the opposite of this by invoking the <kbd>^</kbd> operator, as in the fourth example above. In that case, when <kbd>100x200^</kbd> is given as the argument, again at least one of the dimensions will be attained, but in this case the resulting image can snugly contain the original. Here the <em class="arg">geometry</em> argument gives <em>minimum</em> values. In our example, the height will become 200 and the width will be scaled to preserve the aspect ratio, becoming (640/480)×200 pixels=267 pixels. With the <kbd>^</kbd> operator, one of those dimensions will match the requested size, but the image will likely overflow the dimensions requested to preserve its aspect ratio. (The <kbd>^</kbd> feature is new as of IM 6.3.8-2.)</p>
<p>We see that ImageMagick is very good about preserving aspect ratios of images, to prevent distortion of your favorite photos and images. But you might really want the dimensions to be <kbd>100x200</kbd>, thereby stretching the image. In this case just tell ImageMagick you really mean it (!) by appending an exclamation operator to the geometry. This will force the image size to exactly what you specify. So, for example, if you specify <kbd>100x200!</kbd> the dimensions will become exactly 100x200 (giving a small, vertically elongated wizard).</p>
</dd>
<dt class="doc"> Bounding the width, height, and area; the operators <kbd>></kbd>, <kbd><</kbd>, and <kbd>@</kbd> </dt>
<dd>
Here are a few more examples:
<div class="cmd">
convert logo: -resize "100" wiz1.png
</div> <!-- end cmd -->
<div class="cmd">
convert logo: -resize "x200" wiz2.png
</div> <!-- end cmd -->
<div class="cmd">
convert logo: -resize "100x200>" wiz3.png
</div> <!-- end cmd -->
<div class="cmd">
convert logo: -resize "100x200<" wiz4.png
</div> <!-- end cmd -->
<p>If only one dimension is given it is taken to be the width. When only the width is specified, as in the first example above, the width is accepted as given and the height is chosen to maintain the aspect ratio of the input image. Similarly, if only the height is specified, as in the second example above, the height is accepted and the width is chosen to maintain the aspect ratio.</p>
<p>Use <kbd>></kbd> to change the dimensions of the image <em>only</em> if the original width or height is exeeded by one of the <em class="arg">geometry</em> specifications. Use <kbd><</kbd> to resize the image <em>only</em> if both of the original dimensions are less than the <em class="arg">geometry</em> specifications. In either case, if a change is made, the result is as if the <kbd>></kbd> or <kbd>></kbd> operator was not present. So, in the third example above, we specified <kbd>100x200></kbd> and the original image size is 640x480, so the image size is reduced as if we had specified <kbd>100x200</kbd>. However, in the fourth example above, there will be no change to its size.</p>
<p>Finally, Use <kbd>@</kbd> to specify the maximum area in pixels of an image, again while attempting to preserve aspect ratio. (Pixels take only integer values, so some approximation is always at work.) In the following example, an area of 10000 pixels is requested. The resulting file has dimensions 115x86, which has 9890 pixels. </p>
<div class="cmd">
convert logo: -resize "@10000" wiz10000.png
</div> <!-- end cmd -->
</dd>
<dt class="doc">A word about the quotation marks</dt>
<dd>
<p>In all the examples above and below, we have enclosed the <em class="arg">geometry</em> arguments within quotation marks. Doing so is optional in many cases, but not always. We <em>must</em> enclose the geometry specifications in quotation marks when using <kbd><</kbd> or <kbd>></kbd> to prevent these characters from being interpreted by the shell as <em>file redirection</em>. On Windows systems, the carat <kbd>^</kbd> needs to be within quotes, else it is ignored. To be safe, one should probably maintain a habit of enclosing all <em class="arg">geometry</em> arguments in quotes, as we have here.</p>
</dd>
<dt class="doc">Offsets in geometry</dt>
<dd>
<p>
Here are some examples to illustrate the use of <em>offsets</em> in <em class="arg">geometry</em> arguments. One typical use of offsets is in conjunction with the
<a href="../www/command-line-options.html#region">‑region</a> option. This option allows many other options to modify the pixels within a specified rectangular subregion of an image. As such, it needs to be given the width and height of that region, and also an <em>offset</em> into the image, which is a pair of coordinates that indicate the location of the region within the larger image. Below, in the first example, we specify a region of size <kbd>100x200</kbd> to be located at the <em>xy</em>–coordinates <em>x</em>=10, <em>y</em>=20. Let's use the usual algebraic notation (<em>x</em>,<em>y</em>)=(10,20), for convenience.
</p>
<div class="cmd">
convert logo: -region "100x200+10+20" -negate wizNeg1.png
</div> <!-- end cmd -->
<div class="cmd">
convert logo: -region "100x200-10+20" -negate wizNeg2.png
</div> <!-- end cmd -->
<div class="cmd">
convert logo: -gravity center -region "100x200-10+20" -negate wizNeg3.png
</div> <!-- end cmd -->
<p>Note that offsets always require +/− signs. The offset is not actually a true location within the image; its coordinates must be added to some other location. Let's refer to that as the <em>current location</em>. In the first two examples above, though, that location is the upper-left hand corner of the image, which has coordinates (0,0). (That is the default situation when there are no other directives given to change it.) The first example above puts the <kbd>100x200</kbd> rectangle's own upper-left corner at (10,20). </p>
<p>A negative offset can make sense in many cases. In the second example above, the offset is (-10,20), specified by <kbd>-10+20</kbd>. In that case, only the portion of the (virtual) rectangle obtained that lies within the image can be negated; here it is equivalent to specifying the geometry as <kbd>90x200+0+20</kbd>.</p>
<p>In the third example above, the <a href="../www/command-line-options.html#gravity">‑gravity</a> setting precedes the others and sets the current location within the image at the very center of the image. In this case that is at pixel (320,240), since the size of the image is 640x480. This means that the offsets apply to that location, which thereby gets moved, in this case, to (320-10,240+20)=(310,260). But the <kbd>100x200</kbd> region itself is affected by the <a href="../www/command-line-options.html#gravity">‑gravity</a> setting, so instead of affecting its upper-left corner, the region's own center (at (+50,+100) within it) is determined. Therefore the center of the <kbd>100x200</kbd> rectangle is moved to (310,260). The negated rectangle's upper-left corner is now at (310-50,260-100)=(260,160).
</p>
</dd>
</dl>
<div style="margin: auto;">
<h2><a name="stack"></a>Image Stack</h2>
</div>
<p>In school, your teacher probably permitted you to work on problems on a scrap of paper and then copy the results to your test paper. An image stack is similar. It permits you to work on an image or image sequence in isolation and subsequently introduce the results back into the command line. The image stack is delineated with parenthesis. Image operators only affect images in the current stack. For example, we can limit the image rotation to just the wizard image like this:</p>
<div class="cmd">
convert wand.gif \( wizard.gif -rotate 30 \) +append images.gif
</div> <!-- end cmd -->
<p>Notice that the parentheses are <em>escaped</em> by preceding them with
backslashes. This is required under Unix, where parentheses are special
<em>shell</em> characters. The backslash tells the shell not to interpret
these characters, but to pass them directly to the command being executed. Do
not escape the parentheses under Windows. Each parenthesis (or escaped
parenthesis) must have spaces on either side, as in the example shown
above.</p>
<p>In addition to the image operators already discussed, the following image operators are most useful when processing images in an image stack:</p>
<p class="options">
<span class='bull'> • </span>
<a href="../www/command-line-options.html#clone">‑clone</a> <span class='bull'> • </span><a href="../www/command-line-options.html#delete">‑delete</a> <span class='bull'> • </span><a href="../www/command-line-options.html#insert">‑insert</a> <span class='bull'> • </span><a href="../www/command-line-options.html#swap">‑swap</a> <span class='bull'> • </span>
</p>
<p>The arguments to these operators are indexes into the image sequence by number, starting with zero, for the first image, and so on. However if you give a negative index, the images are indexed from the end (last image added). That is, an index of -1 is the last image in the current image sequence, -2 gives the second-to-last, and so on.</p>
<div style="margin: auto;">
<h2><a name="output"></a>Output Filename</h2>
</div>
<p>ImageMagick extends the concept of an output filename to include:</p>
<ol>
<li>an explicit image format</li>
<li>write to <em>standard out</em></li>
<li>filename references</li>
</ol>
<p>Each of these extensions are explained in the next few paragraphs.</p>
<dl class="doc">
<dt class="doc">Explicit Image Format</dt>
<dd>Images can be stored in a mryiad of image formats including the better known JPEG, PNG, TIFF and others. ImageMagick must know the desired format of the image before it is written. ImageMagick leverages the filename extension to determine the format. For example, <kbd>image.jpg</kbd> tells ImageMagick to write the image in the JPEG format. In some cases the filename does not identify the image format. In these cases, the image is written in the format it was originally read unless an explicit image format is specified. For example, suppose we want to write our image to a filename of <kbd>image</kbd> in the raw red, green, and blue intensity format:
<div class="cmd">
convert image.jpg rgb:image
</div> <!-- end cmd -->
</dd>
<dt class="doc">Standard Out</dt>
<dd>Unix permits the output of one command to be piped to another. ImageMagick permits piping one command to another with a filename of <kbd>-</kbd>. In this example we pipe the output of <a href="../www/convert.html">convert</a> to the <a href="../www/display.html">display</a> program:
<div class="cmd">
convert logo: gif:- | display gif:-
</div> <!-- end cmd -->
Here the explicit format is optional. The GIF image format has a signature that uniquely identifies it so ImageMagick can readily recognize the format as GIF.
</dd>
<dt class="doc">Filename References</dt>
<dd>Optionally, use an embedded formatting character to write a sequential image list. Suppose our output filename is <kbd>image-%d.jpg</kbd> and our image list includes 3 images. You can expect these images files to be written:
<div class="cmdout">
image-0.jpg <br/>
image-1.jpg <br/>
image-2.jpg <br/>
</div> <!-- end cmd -->
Or retrieve image properties to modify the image filename. For example,
<div class="cmd">
convert rose: -set filename:area "%wx%h" 'rose-%[filename:area].png'
</div>
writes this filename:
<div class="cmd">
rose-70x46.png
</div> <!-- end cmd -->
</dd>
</dl>
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