command-line-processing.html revision 7ce65e7125a4e1df1a274ce373c537a9df9c16cd
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The backslash is the Unix <var>line-continuation</var> character. In the Windows shell, use a carat character (<code>^</code>) for line-continuation. We use the Unix style on these web pages, as above. Sometimes, however, the lines are wrapped by your browser if the browser window is small enough, but the command-lines, shown in white, are still intended to be typed as one line. Line continuation characters need not be entered. The <var>parentheses</var> that are <var>escaped</var> 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 discuss some of those issues later, as they arise. </p> 73 74<p>Without knowing much about the ImageMagick command-line, you can probably surmise 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> 75 76<ul> 77 <a href="/images/label.gif"><img src="/images/label.gif" width="78" height="53" alt="label" /></a> 78<img style="margin-top:16px; margin-bottom:17px;" src="/images/right.gif" width="20" height="20" alt="==>" /> 79 <a href="/images/button.gif"> 80 <img src="/images/button.gif" width="78" height="53" alt="button" /></a> 81</ul> 82 83 84<p>Here we show percent completion of a task as a shaded cylinder:</p> 85 86<ul> 87 <img src="/images/cylinder_shaded.png" width="320" height="200" alt="Shaded Cylinder" /> 88</ul> 89 90<p>Given the complexity of the rendering, you might be surprised it is accomplished by a single command-line:</p> 91 92<pre> 93convert -size 320x90 canvas:none -stroke snow4 -size 1x90 -tile gradient:white-snow4 \ 94 -draw 'roundrectangle 16, 5, 304, 85 20,40' +tile -fill snow \ 95 -draw 'roundrectangle 264, 5, 304, 85 20,40' -tile gradient:chartreuse-green \ 96 -draw 'roundrectangle 16, 5, 180, 85 20,40' -tile gradient:chartreuse1-chartreuse3 \ 97 -draw 'roundrectangle 140, 5, 180, 85 20,40' +tile -fill none \ 98 -draw 'roundrectangle 264, 5, 304, 85 20,40' -strokewidth 2 \ 99 -draw 'roundrectangle 16, 5, 304, 85 20,40' \( +clone -background snow4 \ 100 -shadow 80x3+3+3 \) +swap -background none -layers merge \( +size -font Helvetica \ 101 -pointsize 90 -strokewidth 1 -fill red label:'50 %' -trim +repage \( +clone \ 102 -background firebrick3 -shadow 80x3+3+3 \) +swap -background none -layers merge \) \ 103 -insert 0 -gravity center -append -background white -gravity center -extent 320x200 \ 104 cylinder_shaded.png 105</pre> 106 107<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="api.html">program interfaces</a>.</p> 108 109<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> 110 111<h2 class="magick-header"><a id="anatomy"></a>The Anatomy of the Command-line</h2> 112<p>The ImageMagick command-line consists of</p> 113 114<ol> 115<li>one or more required input filenames.</li> 116<li>zero, one, or more image settings.</li> 117<li>zero, one, or more image operators.</li> 118<li>zero, one, or more image sequence operators.</li> 119<li>zero, one, or more image stacks.</li> 120<li>zero or one output image filenames (required by 121<a href="convert.html">convert</a>, 122<a href="composite.html">composite</a>, 123<a href="montage.html">montage</a>, 124<a href="compare.html">compare</a>, 125<a href="import.html">import</a>, 126<a href="conjure.html">conjure</a>). 127</li> 128</ol> 129 130<p>You can find a detailed explanation of each of the constituent parts of the command-line in the sections that follow.</p> 131 132<h2 class="magick-header"><a id="input"></a>Input Filename</h2> 133 134<p>ImageMagick extends the concept of an input filename to include:</p> 135<ul> 136<li>filename globbing</li> 137<li>an explicit image format</li> 138<li>using built-in images and patterns</li> 139<li>STDIN, STDOUT, and file descriptors</li> 140<li>selecting certain frames from an image</li> 141<li>selecting a region of an image</li> 142<li>forcing an inline image resize</li> 143<li>forcing an inline image crop</li> 144<li>using filename references</li> 145</ul> 146 147<p>These extensions are explained in the next few paragraphs.</p> 148 149<h3>Filename Globbing</h3> 150<p>In Unix shells, certain characters such as the asterisk (<code>*</code>) and question mark (<code>?</code>) automagically 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 <code>1.jpg</code>, <code>2.jpg</code>, <code>3.jpg</code>, <code>4.jpg</code>, and <code>5.jpg</code> in your current directory to a GIF animation. You can conveniently refer to all of the JPEG files with this command: 151</p> 152 153<pre> 154convert *.jpg images.gif 155</pre> 156 157<h3>Explicit Image Format</h3> 158<p>Images are stored in a myriad of image formats including 159the better known JPEG, PNG, TIFF and others. ImageMagick must know the format 160of the image before it can be read and processed. Most formats have a 161signature within the image that uniquely identifies the format. Failing 162that, ImageMagick leverages the filename extension to determine the format. 163For example, <code>image.jpg</code> or <code>image.JPG</code> tells ImageMagick 164it is reading an image in the JPEG format. </p> 165 166 <p>In some cases the image may not contain a signature 167and/or the filename does not identify the image format. In these cases an 168explicit image format must be specified. For example, suppose our image 169is named <code>image</code> and contains raw red, green, and blue intensity 170values. ImageMagick has no way to automagically determine the image format 171so we explicitly set one: 172</p> 173 174<pre> 175convert -size 640x480 -depth 8 rgb:image image.png 176</pre> 177 178<h3>Built-in Images and Patterns</h3> 179 180<p>ImageMagick has a number of built-in <a href="formats.html#builtin-images">images</a> and <a href="formats.html#builtin-patterns">patterns</a>. To utilize the checkerboard pattern, for example, use: 181</p> 182 183<pre> 184convert -size 640x480 pattern:checkerboard checkerboard.png 185</pre> 186 187<h3>STDIN, STDOUT, and file descriptors</h3> 188<p>Unix and Windows permit the output of one command to be piped to the input of another. ImageMagick permits image data to be read and written from the <a href="http://en.wikipedia.org/wiki/Standard_streams">standard streams</a> STDIN (<var>standard in</var>) and STDOUT (<var>standard out</var>), respectively, using a pseudo-filename of <code>-</code>. In this example we pipe the output of 189 <a href="convert.html">convert</a> to the <a href="display.html">display</a> program: 190</p> 191 192<pre> 193convert logo: gif:- | display gif:- 194</pre> 195 196<p>The second explicit format "<code>gif:</code>" is optional in the preceding example. The GIF image format has a unique signature within the image so ImageMagick's <a href="display.html">display</a> command can readily recognize the format as GIF. The <a href="convert.html">convert</a> program also accepts STDIN as input in this way: 197</p> 198 199<pre> 200convert rose: gif:- | convert - -resize "200%" bigrose.jpg' 201</pre> 202 203<p>Other pipes can be accessed via their <var>file descriptors</var> (as of version 6.4.9-3). The file descriptors 0, 1, and 2 are reserved for the standard streams STDIN, STDOUT, and STDERR, respectively, but a pipe associated with a file descriptor number <var>N</var>>2 can be accessed using the pseudonym <code>fd:</code><var>N</var>. (The pseudonyms <code>fd:0</code> and <code>fd:1</code> can be used for STDIN and STDOUT.) The next example shows how to append image data piped from files with descriptors 3 and 4 and direct the result to the file with descriptor number 5. 204</p> 205 206<pre> 207convert fd:3 fd:4 -append fd:5 208</pre> 209 210<p>When needed, explicit image formats can be given as mentioned earlier, as in the following. 211</p> 212 213<pre> 214convert gif:fd:3 jpg:fd:4 -append tif:fd:5 215</pre> 216 217<h3>Selecting Frames</h3> 218<p>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 (an animated GIF) contains more than one frame but we only want the first: 219</p> 220 221<pre> 222convert 'images.gif[0]' image.png 223</pre> 224 225<p class="bg-info">Unix shells generally interpret brackets so we enclosed the filename in quotes above. 226In a Windows command shell the brackets are not interpreted but using quotes doesn't hurt. However, in most cases the roles of single-quotes and double-quotes are reversed with respect to Unix and Windows, so Windows users should usually try double-quotes where we display single-quotes, and vice versa. 227</p> 228 229<p>You can read more than one image from a sequence with a frame range. For example, you can extract the first four frames of an image sequence: 230</p> 231 232<pre> 233convert 'images.gif[0-3]' images.mng 234</pre> 235 236<p>Finally, you can read more than one image from a sequence, out-of-order. The next command gets the third image in the sequence, followed by the second, and then the fourth: 237</p> 238 239<pre> 240convert 'images.gif[3,2,4]' images.mng 241</pre> 242 243<p>Notice that in the last two commands, a single image is written. The output in this case, where the image type is MNG, is a multi-frame file because the MNG format supports multiple frames. Had the output format been JPG, which only supports single frames, the output would have consisted of separate frames. More about that below, in the section about the <a href="command-line-processing.html#output">Output Filename</a>. 244</p> 245 246<h3>Selecting an Image Region</h3> 247<p>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: 248</p> 249 250<pre> 251convert -size 6000x4000 -depth 8 \ 252 'rgb:image[600x400+1900+2900]' image.jpg 253</pre> 254 255<p> 256 You can get the same results with the <a href="command-line-options.html#extract">‑extract</a> option: 257</p> 258 259<pre> 260convert -size 6000x4000 -depth 8 \ 261 -extract 600x400+1900+2900 rgb:image image.jpg 262</pre> 263 264<h3>Inline Image Resize</h3> 265<p>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: 266</p> 267 268<pre> 269convert '*.jpg' -resize 120x120 thumbnail%03d.png 270</pre> 271 272<p>Here <var>all</var> the images are read and subsequently 273resized. It is faster and less resource intensive to resize each image it 274is read: 275</p> 276 277<pre> 278convert '*.jpg[120x120]' thumbnail%03d.png 279</pre> 280 281<h3>Inline Image Crop</h3> 282<p>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: 283</p> 284 285<pre> 286convert '*.jpg' -crop 120x120+10+5 thumbnail%03d.png 287</pre> 288 289<p>Here <var>all</var> the images are read and subsequently cropped. It is faster and less resource-intensive to crop each image as it is read: 290</p> 291 292<pre> 293convert '*.jpg[120x120+10+5]' thumbnail%03d.png 294</pre> 295 296 297<h3>Filename References</h3> 298 299<p>There are two methods to use a filename to reference other image filenames. 300The first is with '<code>@</code>' which reads image filenames separated by white space from the specified file. Assume the file <code>myimages.txt</code> consists of a list of filenames, like so: 301</p> 302 303<pre> 304frame001.jpg 305frame002.jpg 306frame003.jpg 307</pre> 308 309<p>We then expect this command:</p> 310 311<pre> 312convert @myimages.txt mymovie.gif 313</pre> 314 315<p>to read the images <code>frame001.jpg</code>, <code>frame002.jpg</code>, and <code>frame003.jpg</code> and convert them to a GIF image sequence. </p> 316<p>If the image path includes one or more spaces, enclose the path in quotes:</p> 317<pre> 318'my title.jpg' 319</pre> 320 321 322 <p>Some ImageMagick command-line <a href="command-line-options.html">options</a> may exceed the capabilities of 323your command-line processor. Windows, for example, limits command-lines 324to 8192 characters. If, for example, you have a draw option with polygon 325points that exceed the command-line length limit, put the draw option instead 326in a file and reference the file with 327the <code>@</code> (e.g. <code>@mypoly.txt</code>).</p> 328 329<p>Another method of referring to other image files is by 330embedding a formatting character in the filename with a scene range. Consider 331the filename <code>image-%d.jpg[1-5]</code>. The command</p> 332 333<pre> 334convert image-%d.jpg[1-5] 335</pre> 336 337<p>causes ImageMagick to attempt to read images with these filenames: 338</p> 339 340<pre> 341image-1.jpg 342image-2.jpg 343image-3.jpg 344image-4.jpg 345image-5.jpg 346</pre> 347 348<h3>Stream Buffering</h3> 349<p>By default, the input stream is buffered. To ensure information on the source file or terminal is read as soon as its available, set the buffer size to 0:</p> 350 351<pre> 352convert logo: gif:- | display -define stream:buffer-size=0 gif:- 353</pre> 354 355<h2 class="magick-header"><a id="setting"></a>Image Setting</h2> 356 357<p>An image setting persists as it appears on the command-line and may affect 358subsequent processing such as reading an image, an image operator, or when 359writing an image as appropriate. An image setting stays in effect until it 360is reset or the command-line terminates. The image settings include:</p> 361 362<ul> 363<a href="command-line-options.html#adjoin">‑adjoin</a> • <a href="command-line-options.html#affine">‑affine</a> • <a href="command-line-options.html#alpha">‑alpha</a> • <a href="command-line-options.html#antialias">‑antialias</a> • <a href="command-line-options.html#authenticate">‑authenticate</a> • <a href="command-line-options.html#background">‑background</a> • <a href="command-line-options.html#bias">‑bias</a> • <a href="command-line-options.html#black-point-compensation">‑black‑point‑compensation</a> • <a href="command-line-options.html#blue-primary">‑blue‑primary</a> • <a href="command-line-options.html#bordercolor">‑bordercolor</a> • <a href="command-line-options.html#caption">‑caption</a> • <a href="command-line-options.html#channel">‑channel</a> • <a href="command-line-options.html#comment">‑comment</a> • <a href="command-line-options.html#compress">‑compress</a> • <a href="command-line-options.html#debug">‑debug</a> • <a href="command-line-options.html#define">‑define</a> • <a href="command-line-options.html#delay">‑delay</a> • <a href="command-line-options.html#density">‑density</a> • <a href="command-line-options.html#depth">‑depth</a> • <a href="command-line-options.html#direction">‑direction</a> • <a href="command-line-options.html#display">‑display</a> • <a href="command-line-options.html#dispose">‑dispose</a> • <a href="command-line-options.html#dither">‑dither</a> • <a href="command-line-options.html#encoding">‑encoding</a> • <a href="command-line-options.html#endian">‑endian</a> • <a href="command-line-options.html#extract">‑extract</a> • <a href="command-line-options.html#family">‑family</a> • <a href="command-line-options.html#fill">‑fill</a> • <a href="command-line-options.html#filter">‑filter</a> • <a href="command-line-options.html#font">‑font</a> • <a href="command-line-options.html#format">‑format</a> • <a href="command-line-options.html#fuzz">‑fuzz</a> • <a href="command-line-options.html#geometry">‑geometry</a> • <a href="command-line-options.html#gravity">‑gravity</a> • <a href="command-line-options.html#green-primary">‑green‑primary</a> • <a href="command-line-options.html#interlace">‑interlace</a> • <a href="command-line-options.html#intent">‑intent</a> • <a href="command-line-options.html#interpolate">‑interpolate</a> • <a href="command-line-options.html#label">‑label</a> • <a href="command-line-options.html#limit">‑limit</a> • <a href="command-line-options.html#linewidth">‑linewidth</a> • <a href="command-line-options.html#log">‑log</a> • <a href="command-line-options.html#loop">‑loop</a> • <a href="command-line-options.html#mask">‑mask</a> • <a href="command-line-options.html#mattecolor">‑mattecolor</a> • <a href="command-line-options.html#monitor">‑monitor</a> • <a href="command-line-options.html#orient">‑orient</a> • <a href="command-line-options.html#page">‑page</a> • <a href="command-line-options.html#pointsize">‑pointsize</a> • <a href="command-line-options.html#preview">‑preview</a> • <a href="command-line-options.html#quality">‑quality</a> • <a href="command-line-options.html#quiet">‑quiet</a> • <a href="command-line-options.html#red-primary">‑red‑primary</a> • <a href="command-line-options.html#region">‑region</a> • <a href="command-line-options.html#render">‑render</a> • <a href="command-line-options.html#repage">‑repage</a> • <a href="command-line-options.html#sampling-factor">‑sampling‑factor</a> • <a href="command-line-options.html#scene">‑scene</a> • <a href="command-line-options.html#seed">‑seed</a> • <a href="command-line-options.html#size">‑size</a> • <a href="command-line-options.html#stretch">‑stretch</a> • <a href="command-line-options.html#stroke">‑stroke</a> • <a href="command-line-options.html#strokewidth">‑strokewidth</a> • <a href="command-line-options.html#style">‑style</a> • <a href="command-line-options.html#texture">‑texture</a> • <a href="command-line-options.html#tile">‑tile</a> • <a href="command-line-options.html#transparent-color">‑transparent‑color</a> • <a href="command-line-options.html#treedepth">‑treedepth</a> • <a href="command-line-options.html#type">‑type</a> • <a href="command-line-options.html#undercolor">‑undercolor</a> • <a href="command-line-options.html#units">‑units</a> • <a href="command-line-options.html#verbose">‑verbose</a> • <a href="command-line-options.html#virtual-pixel">‑virtual‑pixel</a> • <a href="command-line-options.html#weight">‑weight</a> </ul> 364 365<p>In this example, <var>-channel</var> applies to each of the images, since, as we mentioned, settings persist: 366</p> 367 368<pre> 369convert -channel RGB wand.png wizard.png images.png 370</pre> 371 372<h2 class="magick-header"><a id="operator"></a>Image Operator</h2> 373 374<p>An image operator differs from a setting in that it affects the image 375immediately as it appears on the command-line. An operator is 376any command-line <a href="command-line-options.html">option</a> not listed as a 377<a href="command-line-processing.html#setting">image setting</a> or 378<a href="command-line-processing.html#sequence">image sequence operator</a>. Unlike an 379image setting, which persists until the command-line terminates, 380an operator is applied to an image and forgotten. The image operators 381include:</p> 382 383<ul> 384<a href="command-line-options.html#annotate">‑annotate</a> • <a href="command-line-options.html#black-threshold">‑black‑threshold</a> • <a href="command-line-options.html#blur">‑blur</a> • <a href="command-line-options.html#border">‑border</a> • <a href="command-line-options.html#charcoal">‑charcoal</a> • <a href="command-line-options.html#chop">‑chop</a> • <a href="command-line-options.html#clip">‑clip</a> • <a href="command-line-options.html#clip-path">‑clip‑path</a> • <a href="command-line-options.html#clip-mask">‑clip‑mask</a> • <a href="command-line-options.html#colors">‑colors</a> • <a href="command-line-options.html#colorize">‑colorize</a> • <a href="command-line-options.html#colorspace">‑colorspace</a> • <a href="command-line-options.html#compose">‑compose</a> • <a href="command-line-options.html#contrast">‑contrast</a> • <a href="command-line-options.html#convolve">‑convolve</a> • <a href="command-line-options.html#crop">‑crop</a> • <a href="command-line-options.html#cycle">‑cycle</a> • <a href="command-line-options.html#despeckle">‑despeckle</a> • <a href="command-line-options.html#draw">‑draw</a> • <a href="command-line-options.html#edge">‑edge</a> • <a href="command-line-options.html#emboss">‑emboss</a> • <a href="command-line-options.html#enhance">‑enhance</a> • <a href="command-line-options.html#equalize">‑equalize</a> • <a href="command-line-options.html#evaluate">‑evaluate</a> • <a href="command-line-options.html#extent">‑extent</a> • <a href="command-line-options.html#flip">‑flip</a> • <a href="command-line-options.html#flop">‑flop</a> • <a href="command-line-options.html#floodfill">‑floodfill</a> • <a href="command-line-options.html#frame">‑frame</a> • <a href="command-line-options.html#gamma">‑gamma</a> • <a href="command-line-options.html#gaussian-blur">‑gaussian‑blur</a> • <a href="command-line-options.html#implode">‑implode</a> • <a href="command-line-options.html#lat">‑lat</a> • <a href="command-line-options.html#level">‑level</a> • <a href="command-line-options.html#map">‑map</a> • <a href="command-line-options.html#median">‑median</a> • <a href="command-line-options.html#modulate">‑modulate</a> • <a href="command-line-options.html#monochrome">‑monochrome</a> • <a href="command-line-options.html#negate">‑negate</a> • <a href="command-line-options.html#noise">‑noise</a> • <a href="command-line-options.html#normalize">‑normalize</a> • <a href="command-line-options.html#opaque">‑opaque</a> • <a href="command-line-options.html#ordered-dither">‑ordered‑dither</a> • <a href="command-line-options.html#paint">‑paint</a> • <a href="command-line-options.html#posterize">‑posterize</a> • <a href="command-line-options.html#raise">‑raise</a> • <a href="command-line-options.html#profile">‑profile</a> • <a href="command-line-options.html#radial-blur">‑radial‑blur</a> • <a href="command-line-options.html#raise">‑raise</a> • <a href="command-line-options.html#random-threshold">‑random‑threshold</a> • <a href="command-line-options.html#resample">‑resample</a> • <a href="command-line-options.html#resize">‑resize</a> • <a href="command-line-options.html#roll">‑roll</a> • <a href="command-line-options.html#rotate">‑rotate</a> • <a href="command-line-options.html#sample">‑sample</a> • <a href="command-line-options.html#scale">‑scale</a> • <a href="command-line-options.html#sepia-tone">‑sepia‑tone</a> • <a href="command-line-options.html#segment">‑segment</a> • <a href="command-line-options.html#shade">‑shade</a> • <a href="command-line-options.html#shadow">‑shadow</a> • <a href="command-line-options.html#sharpen">‑sharpen</a> • <a href="command-line-options.html#shave">‑shave</a> • <a href="command-line-options.html#shear">‑shear</a> • <a href="command-line-options.html#sigmoidal-contrast">‑sigmoidal‑contrast</a> • <a href="command-line-options.html#solarize">‑solarize</a> • <a href="command-line-options.html#splice">‑splice</a> • <a href="command-line-options.html#spread">‑spread</a> • <a href="command-line-options.html#strip">‑strip</a> • <a href="command-line-options.html#swirl">‑swirl</a> • <a href="command-line-options.html#threshold">‑threshold</a> • <a href="command-line-options.html#transparent">‑transparent</a> • <a href="command-line-options.html#thumbnail">‑thumbnail</a> • <a href="command-line-options.html#tint">‑tint</a> • <a href="command-line-options.html#transform">‑transform</a> • <a href="command-line-options.html#trim">‑trim</a> • <a href="command-line-options.html#unsharp">‑unsharp</a> • <a href="command-line-options.html#version">‑version</a> • <a href="command-line-options.html#wave">‑wave</a> • <a href="command-line-options.html#white-point">‑white‑point</a> • <a href="command-line-options.html#white-threshold">‑white‑threshold</a> </ul> 385 386<p>In this example, <var>-negate</var> negates the wand image but not the wizard:</p> 387 388<pre> 389convert wand.png -negate wizard.png images.png 390</pre> 391 392<h2 class="magick-header"><a id="sequence"></a>Image Sequence Operator</h2> 393 394<p>An image sequence operator differs from a setting in that it affects an 395image sequence immediately as it appears on the command-line. Choose from 396these image sequence operators:</p> 397 398<ul> 399<a href="command-line-options.html#append">‑append</a> • <a href="command-line-options.html#affinity">‑affinity</a> • <a href="command-line-options.html#average">‑average</a> • <a href="command-line-options.html#clut">‑clut</a> • <a href="command-line-options.html#coalesce">‑coalesce</a> • <a href="command-line-options.html#combine">‑combine</a> • <a href="command-line-options.html#compare">‑compare</a> • <a href="command-line-options.html#complex">‑complex</a> • <a href="command-line-options.html#composite">‑composite</a> • <a href="command-line-options.html#copy">‑copy</a> • <a href="command-line-options.html#crop">‑crop</a> • <a href="command-line-options.html#debug">‑debug</a> • <a href="command-line-options.html#deconstruct">‑deconstruct</a> • <a href="command-line-options.html#delete">‑delete</a> • <a href="command-line-options.html#evaluate-sequence">‑evaluate‑sequence</a> • <a href="command-line-options.html#fft">‑fft</a> • <a href="command-line-options.html#flatten">‑flatten</a> • <a href="command-line-options.html#fx">‑fx</a> • <a href="command-line-options.html#hald-clut">‑hald‑clut</a> • <a href="command-line-options.html#ift">‑ift</a> • <a href="command-line-options.html#identify">‑identify</a> • <a href="command-line-options.html#insert">‑insert</a> • <a href="command-line-options.html#layers">‑layers</a> • <a href="command-line-options.html#limit">‑limit</a> • <a href="command-line-options.html#map">‑map</a> • <a href="command-line-options.html#maximum">‑maximum</a> • <a href="command-line-options.html#minimum">‑minimum</a> • <a href="command-line-options.html#morph">‑morph</a> • <a href="command-line-options.html#mosaic">‑mosaic</a> • <a href="command-line-options.html#optimize">‑optimize</a> • <a href="command-line-options.html#print">‑print</a> • <a href="command-line-options.html#process">‑process</a> • <a href="command-line-options.html#quiet">‑quiet</a> • <a href="command-line-options.html#separate">‑separate</a> • <a href="command-line-options.html#swap">‑swap</a> • <a href="command-line-options.html#write">‑write</a> </ul> 400 401<h2 class="magick-header"><a id="geometry"></a>Image Geometry</h2> 402 403<p>Many command-line <a href="command-line-options.html">options</a> take a <var>geometry</var> argument 404to specify such things as the desired width and height of an image and other 405dimensional quantities. Because users want so many variations on the resulting 406dimensions, sizes, and positions of images (and because ImageMagick wants to 407provide them), the <var>geometry</var> argument can take many 408forms. We describe many of these in this section. </p> 409 410<p>The image options and settings that take some form of 411a <var>geometry</var> argument include the following. 412Keep in mind that some of these parse their arguments in slightly 413different ways. See the documentation for the individual option or 414setting for more specifics.</p> 415 416<ul> 417<a href="command-line-options.html#adaptive-resize">‑adaptive‑resize</a> • <a href="command-line-options.html#border">‑border</a> • <a href="command-line-options.html#borderwidth">‑borderwidth</a> • <a href="command-line-options.html#chop">‑chop</a> • <a href="command-line-options.html#crop">‑crop</a> • <a href="command-line-options.html#density">‑density</a> • <a href="command-line-options.html#extent">‑extent</a> • <a href="command-line-options.html#extract">‑extract</a> • <a href="command-line-options.html#frame">‑frame</a> • <a href="command-line-options.html#geometry">‑geometry</a> • <a href="command-line-options.html#iconGeometry">‑iconGeometry</a> • <a href="command-line-options.html#liquid-rescale">‑liquid‑rescale</a> • <a href="command-line-options.html#page">‑page</a> • <a href="command-line-options.html#region">‑region</a> • <a href="command-line-options.html#repage">‑repage</a> • <a href="command-line-options.html#resize">‑resize</a> • <a href="command-line-options.html#sample">‑sample</a> • <a href="command-line-options.html#scale">‑scale</a> • <a href="command-line-options.html#shave">‑shave</a> • <a href="command-line-options.html#splice">‑splice</a> • <a href="command-line-options.html#thumbnail">‑thumbnail</a> • <a href="command-line-options.html#window">‑window</a> </ul> 418 419<p>The <var>geometry</var> 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 <var>size</var>[<var>offset</var>], meaning <var>size</var> is required and <var>offset</var> is optional. Occasionally, [<var>size</var>]<var>offset</var> is possible. In no cases are spaces permitted within the <var>geometry</var> argument.</p> 420 421 422<div class="table-responsive"> 423<table class="table table-condensed table-striped"> 424 <col width="20%"/> <col width="80%"/> 425 <thead> 426 <tr> 427 <th style="text-align:center"><var>size</var></th> 428 <th>General description (actual behavior can vary for different options and settings)</th> 429 </tr> 430 </thead> 431 <tbody> 432 <tr> 433 <td><var>scale</var>%</td> 434 <td>Height and width both scaled by specified percentage.</td> 435 </tr> 436 <tr> 437 <td><var>scale-x</var>%x<var>scale-y</var>%</td> 438 <td>Height and width individually scaled by specified percentages. (Only one % symbol needed.)</td> 439 </tr> 440 <tr> 441 <td><var>width</var></td> 442 <td>Width given, height automagically selected to preserve aspect ratio.</td> 443 </tr> 444 <tr> 445 <td>x<var>height</var></td> 446 <td>Height given, width automagically selected to preserve aspect ratio.</td> 447 </tr> 448 <tr> 449 <td><var>width</var>x<var>height</var></td> 450 <td>Maximum values of height and width given, aspect ratio preserved.</td> 451 </tr> 452 <tr> 453 <td><var>width</var>x<var>height</var>^</td> 454 <td>Minimum values of width and height given, aspect ratio preserved.</td> 455 </tr> 456 <tr> 457 <td><var>width</var>x<var>height</var>!</td> 458 <td>Width and height emphatically given, original aspect ratio ignored.</td> 459 </tr> 460 <tr> 461 <td><var>width</var>x<var>height</var>></td> 462 <td>Shrinks an image with dimension(s) <b>larger</b> than the corresponding <var>width</var> and/or <var>height</var> argument(s).</td> 463 </tr> 464 <tr> 465 <td><var>width</var>x<var>height</var><</td> 466 <td>Enlarges an image with dimension(s) <b>smaller</b> than the corresponding <var>width</var> and/or <var>height</var> argument(s).</td> 467 </tr> 468 <tr> 469 <td><var>area</var>@</td> 470 <td>Resize image to have specified area in pixels. Aspect ratio is preserved.</td> 471 </tr> 472 <tr> 473 <td>{<var>size</var>}{<var>offset</var>}</td> 474 <td>Specifying the <var>offset</var> (default is <code>+0+0</code>). Below, {<var>size</var>} refers to any of the forms above.</td> 475 </tr> 476 <tr> 477 <td>{<var>size</var>}{<var>+-</var>}<var>x</var>{<var>+-</var>}<var>y</var></td> 478 <td>Horizontal and vertical offsets <var>x</var> and <var>y</var>, specified in pixels. Signs are required for both. Offsets are affected by <a href="command-line-options.html#gravity">‑gravity</a> setting. Offsets are not affected by <code>%</code> or other <var>size</var> operators.</td> 479 </tr> 480 </tbody> 481</table></div> 482 483 484<h3>Basic adjustments to width and height; the operators <code>%</code>, <code>^</code>, and <code>!</code> </h3> 485<p>Here, just below, are a few simple examples of <var>geometry</var>, showing how it might be used as an argument to the <a href="command-line-options.html#resize">‑resize</a> option. We'll use the internal image <code>logo:</code> for our input image. 486<a href="/images/logo.png"> 487This fine image</a> is 640 pixels wide and 480 pixels high. We say its <var>dimensions</var> 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 <var>offsets</var> into an image, which will always be <var>x</var>–value followed by <var>y</var>. Just think of your high school algebra classes and the <var>xy</var>–plane. (Well, almost: our <var>y</var>–axis will always go downward!) 488</p> 489 490<pre> 491convert logo: -resize '200%' bigWiz.png 492convert logo: -resize '200x50%' longShortWiz.png 493convert logo: -resize '100x200' notThinWiz.png 494convert logo: -resize '100x200^' biggerNotThinWiz.png 495convert logo: -resize '100x200!' dochThinWiz.png 496</pre> 497 498<p>The first of the four commands is simple—it stretches both the width and height of the input image by <code>200%</code> 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 <code>200</code>% and squashing the height to <code>50%</code>. The resulting image (in this example) has dimensions 1280x240. Notice that the percent symbol needn't be repeated; the following are equivalent: <code>200x50%</code>, <code>200%x50</code>, <code>200%x50%</code>. 499</p> 500 501<p>By default, the width and height given in a <var>geometry</var> argument are <var>maximum</var> 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 <var>aspect ratio</var> (the ratio of its height to its width) of the image. For instance, the third command above "tries" to set the dimensions to <code>100x200</code>. 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> 502 503<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 <code>^</code> operator, as in the fourth example above. In that case, when <code>100x200^</code> 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 <var>geometry</var> argument gives <var>minimum</var> 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 <code>^</code> 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 <code>^</code> feature is new as of IM 6.3.8-2.)</p> 504 505<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 <code>100x200</code>, 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 <code>100x200!</code> the dimensions will become exactly 100x200 (giving a small, vertically elongated wizard).</p> 506 507<h3>Bounding the width, height, and area; the operators <code>></code>, <code><</code>, and <code>@</code> </h3> 508<p> 509Here are a few more examples: 510</p> 511 512<pre> 513convert logo: -resize '100' wiz1.png 514convert logo: -resize 'x200' wiz2.png 515convert logo: -resize '100x200>' wiz3.png 516convert logo: -resize '100x200<' wiz4.png 517</pre> 518 519<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> 520 521 522<p>Use <code>></code> to shrink an image <var>only</var> if its dimension(s) are <b>larger</b> than the corresponding <var>width</var> and/or <var>height</var> arguments. Use <code><</code> to enlarge an image <var>only</var> if its dimension(s) are <b>smaller</b> than the corresponding <var>width</var> and/or <var>height</var> arguments. In either case, if a change is made, the result is as if the <code>></code> or <code><</code> operator was not present. So, in the third example above, we specified <code>100x200></code> and the original image size is 640x480, so the image size is reduced as if we had specified <code>100x200</code>. However, in the fourth example above, there will be no change to its size.</p> 523 524<p>Finally, use <code>@</code> 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> 525 526<pre> 527convert logo: -resize '@10000' wiz10000.png 528</pre> 529 530<p class="bg-info">In all the examples above and below, we have enclosed the <var>geometry</var> arguments within quotation marks. Doing so is optional in many cases, but not always. We <var>must</var> enclose the geometry specifications in quotation marks when using <code><</code> or <code>></code> to prevent these characters from being interpreted by the shell as <var>file redirection</var>. On Windows systems, the carat <code>^</code> needs to be within quotes, else it is ignored. To be safe, one should probably maintain a habit of enclosing all <var>geometry</var> arguments in quotes, as we have here. 531</p> 532 533<h3>Offsets in geometry</h3> 534<p> 535Here are some examples to illustrate the use of <var>offsets</var> in <var>geometry</var> arguments. One typical use of offsets is in conjunction with the 536<a href="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 <var>offset</var> 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 <code>100x200</code> to be located at the <var>xy</var>–coordinates <var>x</var>=10, <var>y</var>=20. Let's use the usual algebraic notation (<var>x</var>,<var>y</var>)=(10,20), for convenience. 537</p> 538 539<pre> 540convert logo: -region '100x200+10+20' -negate wizNeg1.png 541convert logo: -region '100x200-10+20' -negate wizNeg2.png 542convert logo: -gravity center -region '100x200-10+20' \ 543 -negate wizNeg3.png 544</pre> 545 546<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 <var>current location</var>. 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 <code>100x200</code> rectangle's own upper-left corner at (10,20). </p> 547 548<p>A negative offset can make sense in many cases. In the second example above, the offset is (-10,20), specified by <code>-10+20</code>. 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 <code>90x200+0+20</code>.</p> 549 550<p>In the third example above, the <a href="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 <code>100x200</code> region itself is affected by the <a href="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 <code>100x200</code> rectangle is moved to (310,260). The negated rectangle's upper-left corner is now at (310-50,260-100)=(260,160). 551</p> 552 553 554<h2 class="magick-header"><a id="stack"></a>Image Stack</h2> 555 556<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> 557 558<pre> 559convert wand.gif \( wizard.gif -rotate 30 \) +append images.gif 560</pre> 561 562 563<p class="bg-info">Notice again that the parentheses are <var>escaped</var> by preceding them with 564backslashes. This is required under Unix, where parentheses are special 565<var>shell</var> characters. The backslash tells the shell not to interpret 566these characters, but to pass them directly to the command being executed. Do 567not escape the parentheses under Windows. Each parenthesis (or escaped 568parenthesis) must have spaces on either side, as in the example shown 569above.</p> 570 571<p>In addition to the image operators already discussed, the following image operators are most useful when processing images in an image stack:</p> 572 573<ul> 574<a href="command-line-options.html#clone">‑clone</a> • <a href="command-line-options.html#delete">‑delete</a> • <a href="command-line-options.html#insert">‑insert</a> • <a href="command-line-options.html#swap">‑swap</a> </ul> 575 576<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> 577 578<h2 class="magick-header"><a id="output"></a>Output Filename</h2> 579 580<p>ImageMagick extends the concept of an output filename to include:</p> 581 582<ol> 583<li>an explicit image format</li> 584<li>write to <var>standard out</var></li> 585<li>filename references</li> 586</ol> 587 588<p>Each of these extensions are explained in the next few paragraphs.</p> 589 590<h3>Explicit Image Format</h3> 591 <p>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, <code>image.jpg</code> 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 <code>image</code> in the raw red, green, and blue intensity format: 592 </p> 593 594<pre> 595convert image.jpg rgb:image 596</pre> 597 598 599<h3>Standard Out</h3> 600 <p>Unix permits the output of one command to be piped to another. ImageMagick permits piping one command to another with a filename of <code>-</code>. In this example we pipe the output of <a href="convert.html">convert</a> to the <a href="display.html">display</a> program: 601 </p> 602 603<pre> 604convert logo: gif:- | display gif:- 605</pre> 606 607<p>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.</p> 608 609<h3>Filename References</h3> 610<p>Optionally, use an embedded formatting character to write a sequential image list. Suppose our output filename is <code>image-%d.jpg</code> and our image list includes 3 images. You can expect these images files to be written: 611</p> 612 613<pre> 614image-0.jpg 615image-1.jpg 616image-2.jpg 617</pre> 618 619<p>Or retrieve image properties to modify the image filename. For example, the command 620</p> 621 622<pre> 623convert rose: -set filename:area '%wx%h' 'rose-%[filename:area].png' 624</pre> 625 626<p>writes an image with this filename: 627</p> 628 629<pre> 630 rose-70x46.png 631</pre> 632 633<p>Finally to convert multiple JPEG images to individual PDF pages, use:</p> 634 635<pre> 636 convert *.jpg +adjoin page-%d.pdf 637</pre> 638 639<h3>Stream Buffering</h3> 640 641<p>By default, the output stream is buffered. To ensure information appears on the destination file or terminal as soon as written, set the buffer size to 0:</p> 642 643<pre> 644convert -define stream:buffer-size=0 logo: gif:- | display gif:- 645</pre> 646</div> 647 <footer class="magick-footer"> 648 <p><a href="support.html">Donate</a> • 649 <a href="sitemap.html">Sitemap</a> • 650 <a href="links.html">Related</a> • 651 <a href="architecture.html">Architecture</a> 652</p> 653 <p><a href="command-line-processing.html#">Back to top</a> • 654 <a href="http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x89AB63D48277377A">Public Key</a> • 655 <a href="http://nextgen.imagemagick.org/script/contact.php">Contact Us</a></p> 656 <p><small>© 1999-2016 ImageMagick Studio LLC</small></p> 657 </footer> 658</div><!-- /.container --> 659 660 <script src="https://localhost/ajax/libs/jquery/1.11.3/jquery.min.js"></script> 661 <script src="http://nextgen.imagemagick.org/js/magick.html"></script> 662</div> 663</body> 664</html> 665
