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223 224 (function() { 225 var po = document.createElement('script'); 226 po.type = 'text/javascript'; po.async = true; 227 po.src = 'https://apis.google.com/js/plusone.js'; 228 var script = document.getElementsByTagName('script')[0]; 229 script.parentNode.insertBefore(po, script); 230 })(); 231 var gplusone = document.getElementById("gplusone"); 232 gplusone.setAttribute("data-size","medium"); 233 gplusone.setAttribute("data-count","false"); 234 </script> 235</div> 236 237<div class="main"> 238 239 240 241 242<h1>ImageMagick Command-line Processing</h1> 243<p class="navigation-index">[<a href="command-line-processing.html#anatomy">The Anatomy of the Command Line</a> • <a href="command-line-processing.html#input">Input Filename</a> • <a href="command-line-processing.html#setting">Image Setting</a> • <a href="command-line-processing.html#operator">Image Operator</a> • <a href="command-line-processing.html#sequence">Image Sequence Operator</a> • <a href="command-line-processing.html#geometry">Image Geometry</a> • <a href="command-line-processing.html#stack">Image Stack</a> • <a href="command-line-processing.html#output">Output Filename</a>]</p> 244 245<div class="doc-section"> 246 247<p>The ImageMagick command line can be as simple as this.</p> 248 249<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert image.jpg image.png</span></p> 250<p>Or it can be very complex, as in the following.</p> 251 252<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert label.gif +matte \ <br/> 253 \( +clone -shade 110x90 -normalize -negate +clone -compose Plus -composite \) \<br/> 254 \( -clone 0 -shade 110x50 -normalize -channel BG -fx 0 +channel -matte \) \<br/> 255 -delete 0 +swap -compose Multiply -composite button.gif</span></p> 256<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> 257 258<div class="image"> 259 <a href="/images/label.gif"><img src="/images/label.gif" width="78" height="53" alt="label" /></a> 260<img style="margin-top:16px; margin-bottom:17px;" src="/images/right.gif" width="20" height="20" alt="==>" /> 261 <a href="/images/button.gif"> 262 <img src="/images/button.gif" width="78" height="53" alt="button" /></a> 263</div> 264 265<p class="warn">[ <em>A quick word about our formatting of commands:</em> The second example above is long enough that the command must be written across several lines, so we formatted it for clarity by inserting backslashes (<kbd>\</kbd>). The backslash is the Unix <em>line continuation</em> character. In the Windows shell, use a carat character (<kbd>^</kbd>) 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 <em>parentheses</em> 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 discuss some of those issues later, as they arise. ]</p> 266 267<p>Here we show percent completion of a task as a shaded cylinder:</p> 268 269<div class="image"> 270 <img src="/images/cylinder_shaded.png" width="320" height="200" alt="Shaded Cylinder" /> 271</div> 272 273<p>Given the complexity of the rendering, you might be surprised it is accomplished by a single command-line:</p> 274 275<pre class="text"> 276convert -size 320x90 canvas:none -stroke snow4 -size 1x90 -tile gradient:white-snow4 \ 277 -draw 'roundrectangle 16, 5, 304, 85 20,40' +tile -fill snow \ 278 -draw 'roundrectangle 264, 5, 304, 85 20,40' -tile gradient:chartreuse-green \ 279 -draw 'roundrectangle 16, 5, 180, 85 20,40' -tile gradient:chartreuse1-chartreuse3 \ 280 -draw 'roundrectangle 140, 5, 180, 85 20,40' +tile -fill none \ 281 -draw 'roundrectangle 264, 5, 304, 85 20,40' -strokewidth 2 \ 282 -draw 'roundrectangle 16, 5, 304, 85 20,40' \( +clone -background snow4 \ 283 -shadow 80x3+3+3 \) +swap -background none -layers merge \( +size -font Helvetica \ 284 -pointsize 90 -strokewidth 1 -fill red label:'50 %' -trim +repage \( +clone \ 285 -background firebrick3 -shadow 80x3+3+3 \) +swap -background none -layers merge \) \ 286 -insert 0 -gravity center -append -background white -gravity center -extent 320x200 \ 287 cylinder_shaded.png 288</pre> 289 290<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> 291 292<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> 293</div> 294 295<h2><a id="anatomy"></a>The Anatomy of the Command Line</h2> 296<div class="doc-section"> 297<p>The ImageMagick command line consists of</p> 298 299<ol> 300<li>one or more required input filenames.</li> 301<li>zero, one, or more image settings.</li> 302<li>zero, one, or more image operators.</li> 303<li>zero, one, or more image sequence operators.</li> 304<li>zero, one, or more image stacks.</li> 305<li>zero or one output image filenames (required by 306<a href="convert.html">convert</a>, 307<a href="composite.html">composite</a>, 308<a href="montage.html">montage</a>, 309<a href="compare.html">compare</a>, 310<a href="import.html">import</a>, 311<a href="conjure.html">conjure</a>). 312</li> 313</ol> 314 315<p>You can find a detailed explanation of each of the constituent parts of the command line in the sections that follow.</p> 316</div> 317 318<h2><a id="input"></a>Input Filename</h2> 319<div class="doc-section"> 320 321<p>ImageMagick extends the concept of an input filename to include:</p> 322<ul> 323<li>filename globbing</li> 324<li>an explicit image format</li> 325<li>using built-in images and patterns</li> 326<li>STDIN, STDOUT, and file descriptors</li> 327<li>selecting certain frames from an image</li> 328<li>selecting a region of an image</li> 329<li>forcing an inline image resize</li> 330<li>forcing an inline image crop</li> 331<li>using filename references</li> 332</ul> 333 334<p>These extensions are explained in the next few paragraphs.</p> 335 336<h3>Filename Globbing</h3> 337<div class="doc-section"> 338<p>In Unix shells, certain characters such as the asterisk (<kbd>*</kbd>) and question mark (<kbd>?</kbd>) 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 <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: 339</p> 340 341<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert *.jpg images.gif</span></p> 342</div> 343 344<h3>Explicit Image Format</h3> 345<div class="doc-section"> 346<p>Images are stored in a myriad of image formats including 347the better known JPEG, PNG, TIFF and others. ImageMagick must know the format 348of the image before it can be read and processed. Most formats have a 349signature within the image that uniquely identifies the format. Failing 350that, ImageMagick leverages the filename extension to determine the format. 351For example, <kbd>image.jpg</kbd> or <kbd>image.JPG</kbd> tells ImageMagick 352it is reading an image in the JPEG format. </p> 353 354 <p>In some cases the image may not contain a signature 355and/or the filename does not identify the image format. In these cases an 356explicit image format must be specified. For example, suppose our image 357is named <kbd>image</kbd> and contains raw red, green, and blue intensity 358values. ImageMagick has no way to automagically determine the image format 359so we explicitly set one: 360</p> 361 362<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert -size 640x480 -depth 8 rgb:image image.png</span></p> 363 </div> 364 365<h3>Built-in Images and Patterns</h3> 366<div class="doc-section"> 367<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: 368</p> 369 370<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert -size 640x480 pattern:checkerboard checkerboard.png</span></p> 371</div> 372 373<h3>STDIN, STDOUT, and file descriptors</h3> 374<div class="doc-section"> 375<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 (<em>standard in</em>) and STDOUT (<em>standard out</em>), respectively, using a pseudo-filename of <kbd>-</kbd>. In this example we pipe the output of 376 <a href="convert.html">convert</a> to the <a href="display.html">display</a> program: 377</p> 378 379<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert logo: gif:- | display gif:-</span></p> 380<p>The second explicit format "<kbd>gif:</kbd>" 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: 381</p> 382 383<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert rose: gif:- | convert - -resize "200%" bigrose.jpg</span></p> 384<p>Other pipes can be accessed via their <em>file descriptors</em> (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 <em>N</em>>2 can be accessed using the pseudonym <kbd>fd:</kbd><em>N</em>. (The pseudonyms <kbd>fd:0</kbd> and <kbd>fd:1</kbd> 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. 385</p> 386 387<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert fd:3 fd:4 -append fd:5</span></p> 388<p>When needed, explicit image formats can be given as mentioned earlier, as in the following. 389</p> 390 391<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert gif:fd:3 jpg:fd:4 -append tif:fd:5</span></p> 392</div> 393 394<h3>Selecting Frames</h3> 395<div class="doc-section"> 396<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: 397</p> 398 399<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert 'images.gif[0]' image.png</span></p> 400<p class="warn">[Unix shells generally interpret brackets so we enclosed the filename in quotes above. 401In 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.] 402</p> 403 404<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: 405</p> 406 407<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert 'images.gif[0-3]' images.mng</span></p> 408<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: 409</p> 410 411<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert 'images.gif[3,2,4]' images.mng</span></p> 412<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>. 413</p> 414</div> 415 416<h3>Selecting an Image Region</h3> 417<div class="doc-section"> 418<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: 419</p> 420 421<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert -size 6000x4000 -depth 8 \ <br/> 'rgb:image[600x400+1900+2900]' image.jpg</span></p> 422<p> 423 You can get the same results with the <a href="command-line-options.html#extract">‑extract</a> option: 424</p> 425 426<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert -size 6000x4000 -depth 8 \ <br/> -extract 600x400+1900+2900 rgb:image image.jpg</span></p> 427</div> 428 429<h3>Inline Image Resize</h3> 430<div class="doc-section"> 431<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: 432</p> 433 434<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert '*.jpg' -resize 120x120 thumbnail%03d.png</span></p> 435<p>Here <em>all</em> the images are read and subsequently 436resized. It is faster and less resource intensive to resize each image it 437is read: 438</p> 439 440<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert '*.jpg[120x120]' thumbnail%03d.png</span></p> 441</div> 442 443<h3>Inline Image Crop</h3> 444<div class="doc-section"> 445<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: 446</p> 447 448<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert '*.jpg' -crop 120x120+10+5 thumbnail%03d.png</span></p> 449<p>Here <em>all</em> the images are read and subsequently cropped. It is faster and less resource-intensive to crop each image as it is read: 450</p> 451 452<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert '*.jpg[120x120+10+5]' thumbnail%03d.png</span></p> 453</div> 454 455<h3>Filename References</h3> 456<div class="doc-section"> 457<p>There are two methods to use a filename to reference other image filenames. 458The first is with '<kbd>@</kbd>' which reads image filenames separated by white space from the specified file. Assume the file <kbd>myimages.txt</kbd> consists of a list of filenames, like so: 459</p> 460 461<pre class="text"> 462 frame001.jpg 463 frame002.jpg 464 frame003.jpg 465</pre> 466 467<p>We then expect this command:</p> 468<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert @myimages.txt mymovie.gif</span></p><p>to read the images <kbd>frame001.jpg</kbd>, <kbd>frame002.jpg</kbd>, and <kbd>frame003.jpg</kbd> and convert them to a GIF image sequence. </p> 469<p>If the image path includes one or more spaces, enclose the path in quotes:</p> 470<pre class="text"> 471 'my title.jpg' 472</pre> 473 474 475 <p>Some ImageMagick command-line options may exceed the capabilities of 476your command line processor. Windows, for example, limits command lines 477to 8192 characters. If, for example, you have a draw option with polygon 478points that exceed the command-line length limit, put the draw option instead 479in a file and reference the file with 480the <kbd>@</kbd> (e.g. <kbd>@mypoly.txt</kbd>).</p> 481 482<p>Another method of referring to other image files is by 483embedding a formatting character in the filename with a scene range. Consider 484the filename <kbd>image-%d.jpg[1-5]</kbd>. The command</p> 485 486<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert image-%d.jpg[1-5]</span></p> 487<p>causes ImageMagick to attempt to read images with these filenames: 488</p> 489 490<pre class="text"> 491 image-1.jpg 492 image-2.jpg 493 image-3.jpg 494 image-4.jpg 495 image-5.jpg 496</pre> 497 498</div> 499</div> 500 501 502<h2><a id="setting"></a>Image Setting</h2> 503<div class="doc-section"> 504 505<p>An image setting persists as it appears on the command line and may affect 506subsequent processing such as reading an image, an image operator, or when 507writing an image as appropriate. An image setting stays in effect until it 508is reset or the command line terminates. The image settings include:</p> 509 510<p class="options"> 511<a href="command-line-options.html#adjoin">‑adjoin</a> <span class='bull'> • </span> <a href="command-line-options.html#affine">‑affine</a> <span class='bull'> • </span> <a href="command-line-options.html#alpha">‑alpha</a> <span class='bull'> • </span> <a href="command-line-options.html#antialias">‑antialias</a> <span class='bull'> • </span> <a href="command-line-options.html#authenticate">‑authenticate</a> <span class='bull'> • </span> <a href="command-line-options.html#background">‑background</a> <span class='bull'> • </span> <a href="command-line-options.html#bias">‑bias</a> <span class='bull'> • </span> <a href="command-line-options.html#black-point-compensation">‑black‑point‑compensation</a> <span class='bull'> • </span> <a href="command-line-options.html#blue-primary">‑blue‑primary</a> <span class='bull'> • </span> <a href="command-line-options.html#bordercolor">‑bordercolor</a> <span class='bull'> • </span> <a href="command-line-options.html#caption">‑caption</a> <span class='bull'> • </span> <a href="command-line-options.html#channel">‑channel</a> <span class='bull'> • </span> <a href="command-line-options.html#comment">‑comment</a> <span class='bull'> • </span> <a href="command-line-options.html#compress">‑compress</a> <span class='bull'> • </span> <a href="command-line-options.html#debug">‑debug</a> <span class='bull'> • </span> <a href="command-line-options.html#define">‑define</a> <span class='bull'> • </span> <a href="command-line-options.html#delay">‑delay</a> <span class='bull'> • </span> <a href="command-line-options.html#density">‑density</a> <span class='bull'> • </span> <a href="command-line-options.html#depth">‑depth</a> <span class='bull'> • </span> <a href="command-line-options.html#direction">‑direction</a> <span class='bull'> • </span> <a href="command-line-options.html#display">‑display</a> <span class='bull'> • </span> <a href="command-line-options.html#dispose">‑dispose</a> <span class='bull'> • </span> <a href="command-line-options.html#dither">‑dither</a> <span class='bull'> • </span> <a href="command-line-options.html#encoding">‑encoding</a> <span class='bull'> • </span> <a href="command-line-options.html#endian">‑endian</a> <span class='bull'> • </span> <a href="command-line-options.html#extract">‑extract</a> <span class='bull'> • </span> <a href="command-line-options.html#family">‑family</a> <span class='bull'> • </span> <a href="command-line-options.html#fill">‑fill</a> <span class='bull'> • </span> <a href="command-line-options.html#filter">‑filter</a> <span class='bull'> • </span> <a href="command-line-options.html#font">‑font</a> <span class='bull'> • </span> <a href="command-line-options.html#format">‑format</a> <span class='bull'> • </span> <a href="command-line-options.html#fuzz">‑fuzz</a> <span class='bull'> • </span> <a href="command-line-options.html#geometry">‑geometry</a> <span class='bull'> • </span> <a href="command-line-options.html#gravity">‑gravity</a> <span class='bull'> • </span> <a href="command-line-options.html#green-primary">‑green‑primary</a> <span class='bull'> • </span> <a href="command-line-options.html#interlace">‑interlace</a> <span class='bull'> • </span> <a href="command-line-options.html#intent">‑intent</a> <span class='bull'> • </span> <a href="command-line-options.html#interpolate">‑interpolate</a> <span class='bull'> • </span> <a href="command-line-options.html#label">‑label</a> <span class='bull'> • </span> <a href="command-line-options.html#limit">‑limit</a> <span class='bull'> • </span> <a href="command-line-options.html#linewidth">‑linewidth</a> <span class='bull'> • </span> <a href="command-line-options.html#log">‑log</a> <span class='bull'> • </span> <a href="command-line-options.html#loop">‑loop</a> <span class='bull'> • </span> <a href="command-line-options.html#mask">‑mask</a> <span class='bull'> • </span> <a href="command-line-options.html#mattecolor">‑mattecolor</a> <span class='bull'> • </span> <a href="command-line-options.html#monitor">‑monitor</a> <span class='bull'> • </span> <a href="command-line-options.html#orient">‑orient</a> <span class='bull'> • </span> <a href="command-line-options.html#page">‑page</a> <span class='bull'> • </span> <a href="command-line-options.html#pointsize">‑pointsize</a> <span class='bull'> • </span> <a href="command-line-options.html#preview">‑preview</a> <span class='bull'> • </span> <a href="command-line-options.html#quality">‑quality</a> <span class='bull'> • </span> <a href="command-line-options.html#quiet">‑quiet</a> <span class='bull'> • </span> <a href="command-line-options.html#red-primary">‑red‑primary</a> <span class='bull'> • </span> <a href="command-line-options.html#region">‑region</a> <span class='bull'> • </span> <a href="command-line-options.html#render">‑render</a> <span class='bull'> • </span> <a href="command-line-options.html#repage">‑repage</a> <span class='bull'> • </span> <a href="command-line-options.html#sampling-factor">‑sampling‑factor</a> <span class='bull'> • </span> <a href="command-line-options.html#scene">‑scene</a> <span class='bull'> • </span> <a href="command-line-options.html#seed">‑seed</a> <span class='bull'> • </span> <a href="command-line-options.html#size">‑size</a> <span class='bull'> • </span> <a href="command-line-options.html#stretch">‑stretch</a> <span class='bull'> • </span> <a href="command-line-options.html#stroke">‑stroke</a> <span class='bull'> • </span> <a href="command-line-options.html#strokewidth">‑strokewidth</a> <span class='bull'> • </span> <a href="command-line-options.html#style">‑style</a> <span class='bull'> • </span> <a href="command-line-options.html#texture">‑texture</a> <span class='bull'> • </span> <a href="command-line-options.html#tile">‑tile</a> <span class='bull'> • </span> <a href="command-line-options.html#transparent-color">‑transparent‑color</a> <span class='bull'> • </span> <a href="command-line-options.html#treedepth">‑treedepth</a> <span class='bull'> • </span> <a href="command-line-options.html#type">‑type</a> <span class='bull'> • </span> <a href="command-line-options.html#undercolor">‑undercolor</a> <span class='bull'> • </span> <a href="command-line-options.html#units">‑units</a> <span class='bull'> • </span> <a href="command-line-options.html#verbose">‑verbose</a> <span class='bull'> • </span> <a href="command-line-options.html#virtual-pixel">‑virtual‑pixel</a> <span class='bull'> • </span> <a href="command-line-options.html#weight">‑weight</a> </p> 512 513<p>In this example, <em class="arg">-channel</em> applies to each of the images, since, as we mentioned, settings persist: 514</p> 515 516<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert -channel RGB wand.png wizard.png images.png</span></p> 517</div> 518 519<h2><a id="operator"></a>Image Operator</h2> 520<div class="doc-section"> 521 522<p>An image operator differs from a setting in that it affects the image 523immediately as it appears on the command line. An operator is 524any <a href="command-line-options.html">command line option</a> 525not listed as a <a href="command-line-processing.html#setting">image setting</a> 526or <a href="command-line-processing.html#sequence">image sequence operator</a>. Unlike an 527image setting, which persists until the command line terminates, 528an operator is applied to an image and forgotten. The image operators 529include:</p> 530 531<p class="options"> 532<a href="command-line-options.html#annotate">‑annotate</a> <span class='bull'> • </span> <a href="command-line-options.html#black-threshold">‑black‑threshold</a> <span class='bull'> • </span> <a href="command-line-options.html#blur">‑blur</a> <span class='bull'> • </span> <a href="command-line-options.html#border">‑border</a> <span class='bull'> • </span> <a href="command-line-options.html#charcoal">‑charcoal</a> <span class='bull'> • </span> <a href="command-line-options.html#chop">‑chop</a> <span class='bull'> • </span> <a href="command-line-options.html#clip">‑clip</a> <span class='bull'> • </span> <a href="command-line-options.html#clip-path">‑clip‑path</a> <span class='bull'> • </span> <a href="command-line-options.html#clip-mask">‑clip‑mask</a> <span class='bull'> • </span> <a href="command-line-options.html#colors">‑colors</a> <span class='bull'> • </span> <a href="command-line-options.html#colorize">‑colorize</a> <span class='bull'> • </span> <a href="command-line-options.html#colorspace">‑colorspace</a> <span class='bull'> • </span> <a href="command-line-options.html#compose">‑compose</a> <span class='bull'> • </span> <a href="command-line-options.html#contrast">‑contrast</a> <span class='bull'> • </span> <a href="command-line-options.html#convolve">‑convolve</a> <span class='bull'> • </span> <a href="command-line-options.html#crop">‑crop</a> <span class='bull'> • </span> <a href="command-line-options.html#cycle">‑cycle</a> <span class='bull'> • </span> <a href="command-line-options.html#despeckle">‑despeckle</a> <span class='bull'> • </span> <a href="command-line-options.html#draw">‑draw</a> <span class='bull'> • </span> <a href="command-line-options.html#edge">‑edge</a> <span class='bull'> • </span> <a href="command-line-options.html#emboss">‑emboss</a> <span class='bull'> • </span> <a href="command-line-options.html#enhance">‑enhance</a> <span class='bull'> • </span> <a href="command-line-options.html#equalize">‑equalize</a> <span class='bull'> • </span> <a href="command-line-options.html#evaluate">‑evaluate</a> <span class='bull'> • </span> <a href="command-line-options.html#extent">‑extent</a> <span class='bull'> • </span> <a href="command-line-options.html#flip">‑flip</a> <span class='bull'> • </span> <a href="command-line-options.html#flop">‑flop</a> <span class='bull'> • </span> <a href="command-line-options.html#floodfill">‑floodfill</a> <span class='bull'> • </span> <a href="command-line-options.html#frame">‑frame</a> <span class='bull'> • </span> <a href="command-line-options.html#gamma">‑gamma</a> <span class='bull'> • </span> <a href="command-line-options.html#gaussian-blur">‑gaussian‑blur</a> <span class='bull'> • </span> <a href="command-line-options.html#implode">‑implode</a> <span class='bull'> • </span> <a href="command-line-options.html#lat">‑lat</a> <span class='bull'> • </span> <a href="command-line-options.html#level">‑level</a> <span class='bull'> • </span> <a href="command-line-options.html#map">‑map</a> <span class='bull'> • </span> <a href="command-line-options.html#median">‑median</a> <span class='bull'> • </span> <a href="command-line-options.html#modulate">‑modulate</a> <span class='bull'> • </span> <a href="command-line-options.html#monochrome">‑monochrome</a> <span class='bull'> • </span> <a href="command-line-options.html#negate">‑negate</a> <span class='bull'> • </span> <a href="command-line-options.html#noise">‑noise</a> <span class='bull'> • </span> <a href="command-line-options.html#normalize">‑normalize</a> <span class='bull'> • </span> <a href="command-line-options.html#opaque">‑opaque</a> <span class='bull'> • </span> <a href="command-line-options.html#ordered-dither">‑ordered‑dither</a> <span class='bull'> • </span> <a href="command-line-options.html#paint">‑paint</a> <span class='bull'> • </span> <a href="command-line-options.html#posterize">‑posterize</a> <span class='bull'> • </span> <a href="command-line-options.html#raise">‑raise</a> <span class='bull'> • </span> <a href="command-line-options.html#profile">‑profile</a> <span class='bull'> • </span> <a href="command-line-options.html#radial-blur">‑radial‑blur</a> <span class='bull'> • </span> <a href="command-line-options.html#raise">‑raise</a> <span class='bull'> • </span> <a href="command-line-options.html#random-threshold">‑random‑threshold</a> <span class='bull'> • </span> <a href="command-line-options.html#resample">‑resample</a> <span class='bull'> • </span> <a href="command-line-options.html#resize">‑resize</a> <span class='bull'> • </span> <a href="command-line-options.html#roll">‑roll</a> <span class='bull'> • </span> <a href="command-line-options.html#rotate">‑rotate</a> <span class='bull'> • </span> <a href="command-line-options.html#sample">‑sample</a> <span class='bull'> • </span> <a href="command-line-options.html#scale">‑scale</a> <span class='bull'> • </span> <a href="command-line-options.html#sepia-tone">‑sepia‑tone</a> <span class='bull'> • </span> <a href="command-line-options.html#segment">‑segment</a> <span class='bull'> • </span> <a href="command-line-options.html#shade">‑shade</a> <span class='bull'> • </span> <a href="command-line-options.html#shadow">‑shadow</a> <span class='bull'> • </span> <a href="command-line-options.html#sharpen">‑sharpen</a> <span class='bull'> • </span> <a href="command-line-options.html#shave">‑shave</a> <span class='bull'> • </span> <a href="command-line-options.html#shear">‑shear</a> <span class='bull'> • </span> <a href="command-line-options.html#sigmoidal-contrast">‑sigmoidal‑contrast</a> <span class='bull'> • </span> <a href="command-line-options.html#solarize">‑solarize</a> <span class='bull'> • </span> <a href="command-line-options.html#splice">‑splice</a> <span class='bull'> • </span> <a href="command-line-options.html#spread">‑spread</a> <span class='bull'> • </span> <a href="command-line-options.html#strip">‑strip</a> <span class='bull'> • </span> <a href="command-line-options.html#swirl">‑swirl</a> <span class='bull'> • </span> <a href="command-line-options.html#threshold">‑threshold</a> <span class='bull'> • </span> <a href="command-line-options.html#transparent">‑transparent</a> <span class='bull'> • </span> <a href="command-line-options.html#thumbnail">‑thumbnail</a> <span class='bull'> • </span> <a href="command-line-options.html#tint">‑tint</a> <span class='bull'> • </span> <a href="command-line-options.html#transform">‑transform</a> <span class='bull'> • </span> <a href="command-line-options.html#trim">‑trim</a> <span class='bull'> • </span> <a href="command-line-options.html#unsharp">‑unsharp</a> <span class='bull'> • </span> <a href="command-line-options.html#version">‑version</a> <span class='bull'> • </span> <a href="command-line-options.html#wave">‑wave</a> <span class='bull'> • </span> <a href="command-line-options.html#white-point">‑white‑point</a> <span class='bull'> • </span> <a href="command-line-options.html#white-threshold">‑white‑threshold</a> </p> 533 534<p>In this example, <em class="arg">-negate</em> negates the wand image but not the wizard:</p> 535 536<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert wand.png -negate wizard.png images.png</span></p></div> 537 538<h2><a id="sequence"></a>Image Sequence Operator</h2> 539<div class="doc-section"> 540 541<p>An image sequence operator differs from a setting in that it affects an 542image sequence immediately as it appears on the command line. Choose from 543these image sequence operators:</p> 544 545<p class="options"> 546<a href="command-line-options.html#append">‑append</a> <span class='bull'> • </span> <a href="command-line-options.html#affinity">‑affinity</a> <span class='bull'> • </span> <a href="command-line-options.html#average">‑average</a> <span class='bull'> • </span> <a href="command-line-options.html#clut">‑clut</a> <span class='bull'> • </span> <a href="command-line-options.html#coalesce">‑coalesce</a> <span class='bull'> • </span> <a href="command-line-options.html#combine">‑combine</a> <span class='bull'> • </span> <a href="command-line-options.html#composite">‑composite</a> <span class='bull'> • </span> <a href="command-line-options.html#crop">‑crop</a> <span class='bull'> • </span> <a href="command-line-options.html#debug">‑debug</a> <span class='bull'> • </span> <a href="command-line-options.html#deconstruct">‑deconstruct</a> <span class='bull'> • </span> <a href="command-line-options.html#delete">‑delete</a> <span class='bull'> • </span> <a href="command-line-options.html#evaluate-seqence">‑evaluate‑seqence</a> <span class='bull'> • </span> <a href="command-line-options.html#fft">‑fft</a> <span class='bull'> • </span> <a href="command-line-options.html#flatten">‑flatten</a> <span class='bull'> • </span> <a href="command-line-options.html#fx">‑fx</a> <span class='bull'> • </span> <a href="command-line-options.html#hald-clut">‑hald‑clut</a> <span class='bull'> • </span> <a href="command-line-options.html#ift">‑ift</a> <span class='bull'> • </span> <a href="command-line-options.html#identify">‑identify</a> <span class='bull'> • </span> <a href="command-line-options.html#insert">‑insert</a> <span class='bull'> • </span> <a href="command-line-options.html#layers">‑layers</a> <span class='bull'> • </span> <a href="command-line-options.html#limit">‑limit</a> <span class='bull'> • </span> <a href="command-line-options.html#map">‑map</a> <span class='bull'> • </span> <a href="command-line-options.html#maximum">‑maximum</a> <span class='bull'> • </span> <a href="command-line-options.html#minimum">‑minimum</a> <span class='bull'> • </span> <a href="command-line-options.html#morph">‑morph</a> <span class='bull'> • </span> <a href="command-line-options.html#mosaic">‑mosaic</a> <span class='bull'> • </span> <a href="command-line-options.html#optimize">‑optimize</a> <span class='bull'> • </span> <a href="command-line-options.html#print">‑print</a> <span class='bull'> • </span> <a href="command-line-options.html#process">‑process</a> <span class='bull'> • </span> <a href="command-line-options.html#quiet">‑quiet</a> <span class='bull'> • </span> <a href="command-line-options.html#separate">‑separate</a> <span class='bull'> • </span> <a href="command-line-options.html#swap">‑swap</a> <span class='bull'> • </span> <a href="command-line-options.html#write">‑write</a> </p> 547</div> 548 549<h2><a id="geometry"></a>Image Geometry</h2> 550<div class="doc-section"> 551 552<p>Many command-line options take a <em class="arg">geometry</em> argument 553to specify such things as the desired width and height of an image and other 554dimensional quantities. Because users want so many variations on the resulting 555dimensions, sizes, and positions of images (and because ImageMagick wants to 556provide them), the <em class="arg">geometry</em> argument can take many 557forms. We describe many of these in this section. </p> 558 559<p>The image options and settings that take some form of 560a <em class="arg">geometry</em> argument include the following. 561Keep in mind that some of these parse their arguments in slightly 562different ways. See the documentation for the individual option or 563setting for more specifics.</p> 564 565<p class="options" style="text-align:justify"> 566<a href="command-line-options.html#adaptive-resize">‑adaptive‑resize</a> <span class='bull'> • </span> <a href="command-line-options.html#border">‑border</a> <span class='bull'> • </span> <a href="command-line-options.html#borderwidth">‑borderwidth</a> <span class='bull'> • </span> <a href="command-line-options.html#chop">‑chop</a> <span class='bull'> • </span> <a href="command-line-options.html#crop">‑crop</a> <span class='bull'> • </span> <a href="command-line-options.html#density">‑density</a> <span class='bull'> • </span> <a href="command-line-options.html#extent">‑extent</a> <span class='bull'> • </span> <a href="command-line-options.html#extract">‑extract</a> <span class='bull'> • </span> <a href="command-line-options.html#frame">‑frame</a> <span class='bull'> • </span> <a href="command-line-options.html#geometry">‑geometry</a> <span class='bull'> • </span> <a href="command-line-options.html#iconGeometry">‑iconGeometry</a> <span class='bull'> • </span> <a href="command-line-options.html#liquid-rescale">‑liquid‑rescale</a> <span class='bull'> • </span> <a href="command-line-options.html#page">‑page</a> <span class='bull'> • </span> <a href="command-line-options.html#region">‑region</a> <span class='bull'> • </span> <a href="command-line-options.html#repage">‑repage</a> <span class='bull'> • </span> <a href="command-line-options.html#resize">‑resize</a> <span class='bull'> • </span> <a href="command-line-options.html#sample">‑sample</a> <span class='bull'> • </span> <a href="command-line-options.html#scale">‑scale</a> <span class='bull'> • </span> <a href="command-line-options.html#shave">‑shave</a> <span class='bull'> • </span> <a href="command-line-options.html#splice">‑splice</a> <span class='bull'> • </span> <a href="command-line-options.html#thumbnail">‑thumbnail</a> <span class='bull'> • </span> <a href="command-line-options.html#window">‑window</a> </p> 567 568<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> 569 570 571<table id="geometryTable" class="doc"> 572 <col width="20%"/> <col width="80%"/> 573 <thead> 574 <tr valign="top"> 575 <th style="text-align:center"><em class="arg">size</em></th> 576 <th>General description (actual behavior can vary for different options and settings)</th> 577 </tr> 578 </thead> 579 <tbody> 580 <tr valign="top"> 581 <td><em class="arg">scale</em>%</td> 582 <td>Height and width both scaled by specified percentage.</td> 583 </tr> 584 <tr valign="top"> 585 <td><em class="arg">scale-x</em>%x<em class="arg">scale-y</em>%</td> 586 <td>Height and width individually scaled by specified percentages. (Only one % symbol needed.)</td> 587 </tr> 588 <tr valign="top"> 589 <td><em class="arg">width</em></td> 590 <td>Width given, height automagically selected to preserve aspect ratio.</td> 591 </tr> 592 <tr valign="top"> 593 <td>x<em class="arg">height</em></td> 594 <td>Height given, width automagically selected to preserve aspect ratio.</td> 595 </tr> 596 <tr valign="top"> 597 <td><em class="arg">width</em>x<em class="arg">height</em></td> 598 <td>Maximum values of height and width given, aspect ratio preserved.</td> 599 </tr> 600 <tr valign="top"> 601 <td><em class="arg">width</em>x<em class="arg">height</em>^</td> 602 <td>Minimum values of width and height given, aspect ratio preserved.</td> 603 </tr> 604 <tr valign="top"> 605 <td><em class="arg">width</em>x<em class="arg">height</em>!</td> 606 <td>Width and height emphatically given, original aspect ratio ignored.</td> 607 </tr> 608 <tr valign="top"> 609 <td><em class="arg">width</em>x<em class="arg">height</em>></td> 610 <td>Shrinks images with dimension(s) larger than the corresponding <em class="arg">width</em> and/or <em class="arg">height</em> dimension(s).</td> 611 </tr> 612 <tr valign="top"> 613 <td><em class="arg">width</em>x<em class="arg">height</em><</td> 614 <td>Enlarges images with dimension(s) smaller than the corresponding <em class="arg">width</em> and/or <em class="arg">height</em> dimension(s).</td> 615 </tr> 616 <tr valign="top"> 617 <td><em class="arg">area</em>@</td> 618 <td>Resize image to have specified area in pixels. Aspect ratio is preserved.</td> 619 </tr> 620 </tbody> 621 </table> 622 <table class="doc"> 623 <col width="20%"/> <col width="80%"/> 624 <thead> 625 <tr valign="top"> 626 <th style="text-align:center">{<em class="arg">size</em>}{<em class="arg">offset</em>}</th> 627 <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> 628 </tr> 629 </thead> 630 631 <tbody> 632 <tr valign="top"> 633 <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> 634 <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="command-line-options.html#gravity">‑gravity</a> setting. Offsets are not affected by <kbd>%</kbd> or other <em class="arg">size</em> operators.</td> 635 </tr> 636 </tbody> 637</table> 638 639 640<h3>Basic adjustments to width and height; the operators <kbd>%</kbd>, <kbd>^</kbd>, and <kbd>!</kbd> </h3> 641<div class="doc-section"> 642<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="command-line-options.html#resize">‑resize</a> option. We'll use the internal image <kbd>logo:</kbd> for our input image. 643<a href="/images/logo.png"> 644This 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!) 645</p> 646 647<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert logo: -resize '200%' bigWiz.png</span></p> 648<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert logo: -resize '200x50%' longShortWiz.png</span></p> 649<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert logo: -resize '100x200' notThinWiz.png</span></p> 650<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert logo: -resize '100x200^' biggerNotThinWiz.png</span></p> 651<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert logo: -resize '100x200!' dochThinWiz.png</span></p> 652 653<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>. 654</p> 655 656<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> 657 658<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> 659 660<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> 661</div> 662 663<h3>Bounding the width, height, and area; the operators <kbd>></kbd>, <kbd><</kbd>, and <kbd>@</kbd> </h3> 664<div class="doc-section"> 665<p> 666Here are a few more examples: 667</p> 668 669<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert logo: -resize '100' wiz1.png</span></p> 670<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert logo: -resize 'x200' wiz2.png</span></p> 671<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert logo: -resize '100x200>' wiz3.png</span></p> 672<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert logo: -resize '100x200<' wiz4.png</span></p> 673<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> 674 675 676<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 the original dimensions are more 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> 677 678<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> 679 680<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert logo: -resize '@10000' wiz10000.png</span></p> 681<p class="warn">Another word about the quotation marks: 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. 682</p> 683</div> 684 685<h3>Offsets in geometry</h3> 686<div class="doc-section"> 687<p> 688Here 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 689<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 <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. 690</p> 691 692<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert logo: -region '100x200+10+20' -negate wizNeg1.png</span></p> 693<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert logo: -region '100x200-10+20' -negate wizNeg2.png</span></p> 694<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert logo: -gravity center -region '100x200-10+20' \ <br/> -negate wizNeg3.png</span></p> 695 696<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> 697 698<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> 699 700<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 <kbd>100x200</kbd> 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 <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). 701</p> 702</div> 703</div> 704 705 706<h2><a id="stack"></a>Image Stack</h2> 707<div class="doc-section"> 708 709<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> 710 711<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert wand.gif \( wizard.gif -rotate 30 \) +append images.gif</span></p> 712 713<p class="warn">Notice again that the parentheses are <em>escaped</em> by preceding them with 714backslashes. This is required under Unix, where parentheses are special 715<em>shell</em> characters. The backslash tells the shell not to interpret 716these characters, but to pass them directly to the command being executed. Do 717not escape the parentheses under Windows. Each parenthesis (or escaped 718parenthesis) must have spaces on either side, as in the example shown 719above.</p> 720 721<p>In addition to the image operators already discussed, the following image operators are most useful when processing images in an image stack:</p> 722 723<p class="options"> 724<span class='bull'> • </span> 725<a href="command-line-options.html#clone">‑clone</a> <span class='bull'> • </span> <a href="command-line-options.html#delete">‑delete</a> <span class='bull'> • </span> <a href="command-line-options.html#insert">‑insert</a> <span class='bull'> • </span> <a href="command-line-options.html#swap">‑swap</a> <span class='bull'> • </span> 726</p> 727 728<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> 729 730</div> <!-- end Image Stack section --> 731 732<h2><a id="output"></a>Output Filename</h2> 733<div class="doc-section"> 734 735<p>ImageMagick extends the concept of an output filename to include:</p> 736 737<ol> 738<li>an explicit image format</li> 739<li>write to <em>standard out</em></li> 740<li>filename references</li> 741</ol> 742 743<p>Each of these extensions are explained in the next few paragraphs.</p> 744 745<h3>Explicit Image Format</h3> 746<div class="doc-section"> 747 <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, <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: 748 </p> 749 750<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert image.jpg rgb:image</span></p> 751</div> 752 753<h3>Standard Out</h3> 754<div class="doc-section"> 755 <p>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="convert.html">convert</a> to the <a href="display.html">display</a> program: 756 </p> 757 758<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert logo: gif:- | display gif:-</span></p> 759<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. 760</p> 761</div> 762 763<h3>Filename References</h3> 764<div class="doc-section"> 765<p>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: 766</p> 767 768<pre class="text"> 769 image-0.jpg 770 image-1.jpg 771 image-2.jpg 772</pre> 773 774<p>Or retrieve image properties to modify the image filename. For example, the command 775</p> 776 777<p class='crt'><span class="crtprompt"> $ </span><span class='crtin'>convert rose: -set filename:area '%wx%h' \ <br/> 'rose-%[filename:area].png'</span></p> 778<p>writes an image with this filename: 779</p> 780 781<pre class="text"> 782 rose-70x46.png 783</pre> 784 785<p>Finally to convert multiple JPEG images to individual PDF pages, use:</p> 786 787<pre class="text"> 788 convert *.jpg +adjoin page-%d.pdf 789</pre> 790 791</div> 792 793</div> <!-- end Output Filename section --> 794 795</div> 796 797<div id="linkbar"> 798 <span id="linkbar-west"> </span> 799 <span id="linkbar-center"> 800 <a href="/discourse-server">Discourse Server</a> • 801 <a href="http://www.imagemagick.org/MagickStudio/scripts/MagickStudio.cgi">Studio</a> 802 </span> 803 <span id="linkbar-east"> </span> 804 </div> 805 <div class="footer"> 806 <span id="footer-west">© 1999-2012 ImageMagick Studio LLC</span> 807 <span id="footer-east"> <a href="contact.html">Contact the Wizards</a></span> 808 </div> 809 <div style="clear: both; margin: 0; width: 100%; "></div> 810 <script type="text/javascript"> 811 var _gaq = _gaq || []; 812 _gaq.push(['_setAccount', 'UA-17690367-1']); 813 _gaq.push(['_trackPageview']); 814 815 (function() { 816 var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; 817 ga.src = ('https:' == document.location.protocol ? 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