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Use Fx to:</p> 216 217<ul> 218 <li>create canvases, gradients, mathematical colormaps</li> 219 <li>move color values between images and channels</li> 220 <li>translate, flip, mirror, rotate, scale, shear and generally distort images</li> 221 <li>merge or composite multiple images together</li> 222 <li>convolve or merge neighboring pixels together</li> 223 <li>generate image metrics or 'fingerprints'</li> 224</ul> 225 226<p>The expression can be simple:</p> 227 228<p class='crt'><span class="crtprompt"> $magick> </span><span class='crtin'>convert -size 64x64 canvas:black -channel blue -fx "1/2" fx_navy.png</span></p> 229<p>Here, we convert a black to a navy blue image:</p> 230 231<p class="image"> 232 <a href="/images/black.png"><img src="/images/black.png" width="64" height="64" alt="black" /></a> 233 <img style="margin-top:22px; margin-bottom:22px;" src="/images/right.gif" width="20" height="20" alt="==>" /> 234 <a href="/images/navy.png"><img src="/images/navy.png" width="64" height="64" alt="navy" /></a> 235</p> 236 237<p>Or the expression can be complex:</p> 238 239<p class='crt'><span class="crtprompt"> $magick> </span><span class='crtin'>convert rose.jpg \ <br/> 240 -fx "(1.0/(1.0+exp(10.0*(0.5-u)))-0.006693)*1.0092503" \ <br/> 241 rose-sigmoidal.png</span></p> 242<p>This expression results in a high contrast version of the image:</p> 243 244<p class="image"> 245 <a href="/images/rose.jpg"><img src="/images/rose.jpg" width="70" height="46" alt="rose" /></a> 246 <img style="margin-top:13px; margin-bottom:13px;" src="/images/right.gif" width="20" height="20" alt="==>" /> 247 <a href="/images/rose-sigmoidal.png"><img src="/images/rose-sigmoidal.png" width="70" height="46" alt="rose-sigmoidal" /></a> 248</p> 249 250<p>The expression can include variable assignments. Assignments, in most cases, reduce the complexity of an expression and permit some operations that might not be possible any other way. For example, lets create a radial gradient:</p> 251 252<p class='crt'><span class="crtprompt"> $magick> </span><span class='crtin'>convert -size 70x70 canvas: \ <br/> 253 -fx "Xi=i-w/2; Yj=j-h/2; 1.2*(0.5-hypot(Xi,Yj)/70.0)+0.5" \ <br/> 254 radial-gradient.png</span></p> 255<p>The command above returns this image:</p> 256 257<p class="image"> 258 <a href="/images/radial-gradient.png"><img src="/images/radial-gradient.png" width="70" height="70" alt="radial-gradient" /></a> 259</p> 260 261<p>This FX expression adds random noise to an image:</p> 262 263<p class='crt'><span class="crtprompt"> $magick> </span><span class='crtin'>convert photo.jpg -fx 'iso=32; rone=rand(); rtwo=rand(); \<br /> 264 myn=sqrt(-2*ln(rone))*cos(2*Pi*rtwo); myntwo=sqrt(-2*ln(rtwo))* \<br /> 265 cos(2*Pi*rone); pnoise=sqrt(p)*myn*sqrt(iso)* \ <br /> 266 channel(4.28,3.86,6.68,0)/255; max(0,p+pnoise)' noisy.png</span></p> 267<p>See <a href="http://www.imagemagick.org/Usage/transform/index.html#fx">Using FX, The Special Effects Image Operator</a> for more examples.</p> 268 269<p>The next section discusses the Fx expression language.</p> 270 271</div> 272 273<h2><a id="anatomy"></a>The Anatomy of an Fx Expression</h2> 274<div class="doc-section"> 275 276<h3>The Fx Expression Language</h3> 277<div class="doc-section"> 278 279<p>The formal Fx expression language is defined here:</p> 280 281<dl class="doc"> 282 <dt class="doc"> numbers:</dt> 283 <dd> integer, floating point, or scientfic notation (+/- required, e.g. 3.81469e-06)</dd> 284 <dt class="doc"> constants: </dt> 285 <dd> e, Epsilon, QuantumRange, QuantumScale, Opaque, Pi, Transparent</dd> 286 <dt class="doc"> Fx operators (in order of precedence): </dt> 287 <dd> ^ (power), unary -, *, /, % (modulo), +, -, 288 <<, >>, <, <=, >, >=, ==, !=, 289 & (bitwise AND), | (bitwise OR), 290 && (logical AND), || (logical OR), 291 ~ (logical NOT), ?: (ternary conditional)</dd> 292 <dt class="doc"> math functions: </dt> 293 <dd> abs(), acos(), airy(), alt(), asin(), atan(), atan2(), ceil(), cos(), cosh(), debug(), exp(), floor(), 294 hypot(), int(), j0(), j1(), jinc(), ln(), log(), logtwo(), max(), min(), mod(), pow(), rand(), round(), 295 sign(), sin(), sinc(), sinh(), sqrt(), tan(), tanh(), trunc()</dd> 296 <dt class="doc"> channel functions: </dt> 297 <dd> channel(r,g,b,a), channel(c,m,y,k,a)</dd> 298 <dt class="doc"> color names:</dt> 299 <dd> red, cyan, black, etc.</dd> 300 <dt class="doc"> color functions:</dt> 301 <dd> rgb(), rgba(), cmyk(), cmyka(), hsl(), hsla()</dd> 302 <dt class="doc"> color hex values:</dt> 303 <dd> #ccc, #cbfed0, #b9e1cc00</dd> 304 <dt class="doc"> symbols:</dt> 305 <dd style="white-space:pre"> 306 s = current image in sequence 307 t = scene number of current image in sequence 308 u = first image in sequence 309 v = second image in sequence 310 n = number of images in sequence 311 312 i = column offset 313 j = row offset 314 p = pixel to use (absolute or relative to current pixel) 315 316 w = width of this image 317 h = height of this image 318 z = channel depth 319 320 r = red value (from RGBA), of a specific or current pixel 321 g = green '' 322 b = blue '' 323 a = alpha '' 324 o = opacity '' 325 326 c = cyan value of CMYK color of pixel 327 y = yellow '' 328 m = magenta '' 329 k = black '' 330 331 intensity = pixel intensity 332 333 hue = pixel hue 334 saturation = pixel saturation 335 lightness = pixel lightness 336 luminance = pixel luminance 337 338 page.width = page width 339 page.height = page height 340 page.x = page x offset 341 page.y = page y offset 342 343 resolution.x = x resolution 344 resolution.y = y resolution 345 346 depth = image depth 347 minima = image minima 348 maxima = image maxima 349 mean = image mean 350 standard_deviation = image standard deviation 351 kurtosis = image kurtosis 352 skewness = image skewness 353 (add a channel specifier to compute a statistic for that channel, e.g. depth.r) 354 </dd> 355</dl> 356 357</div> 358 359<h3>The Fx Expression</h3> 360<div class="doc-section"> 361 362<p>An Fx expression may include any combination of the following:</p> 363<ul> 364<li> <em>x</em> <kbd>^</kbd> <em>y</em>: exponentiation (<em>x<sup>y</sup></em>)</li> 365<li> <kbd>(</kbd> ... <kbd>)</kbd>: grouping</li> 366<li> <em>x</em> <kbd>*</kbd> <em>y</em>: multiplication (the asterisk <kbd>*</kbd> is optional, for example, <kbd>2u</kbd> or <kbd>2(x+y)</kbd> are acceptable)</li> 367<li> <em>x</em> <kbd>/</kbd> <em>y</em>: division</li> 368<li> <em>x</em> <kbd>%</kbd> <em>y</em>: modulo</li> 369<li> <em>x</em> <kbd>+</kbd> <em>y</em>: addition</li> 370<li> <em>x</em> <kbd>-</kbd> <em>y</em>: subtraction</li> 371<li> <em>x</em> <kbd><<</kbd> <em>y</em>: left shift</li> 372<li> <em>x</em> <kbd>>></kbd> <em>y</em>: right shift</li> 373<li> <em>x</em> <kbd><</kbd> <em>y</em>: boolean relation, return value 1.0 if <em>x</em> < <em>y</em>, otherwise 0.0</li> 374<li> <em>x</em> <kbd><=</kbd> <em>y</em>: boolean relation, return value 1.0 if <em>x</em> <= <em>y</em>, otherwise 0.0</li> 375<li> <em>x</em> <kbd>></kbd> <em>y</em>: boolean relation, return value 1.0 if <em>x</em> > <em>y</em>, otherwise 0.0</li> 376<li> <em>x</em> <kbd>>=</kbd> <em>y</em>: boolean relation, return value 1.0 if <em>x</em> >= <em>y</em>, otherwise 0.0</li> 377<li> <em>x</em> <kbd>==</kbd> <em>y</em>: boolean relation, return value 1.0 if <em>x </em>==<em> y</em>, otherwise 0.0</li> 378<li> <em>x</em> <kbd>!=</kbd> <em>y</em>: boolean relation, return value 1.0 if <em>x </em>!=<em> y</em>, otherwise 0.0</li> 379<li> <em>x</em> <kbd>&</kbd> <em>y</em>: binary AND</li> 380<li> <em>x</em> <kbd>|</kbd> <em>y</em>: binary OR</li> 381<li> <em>x</em> <kbd>&&</kbd> <em>y</em>: logical AND connective, return value 1.0 if <em>x</em> > 0 and <em>y</em> > 0, otherwise 0.0</li> 382<li> <em>x</em> <kbd>||</kbd> <em>y</em>: logical OR connective (inclusive), return value 1.0 if <em>x</em> > 0 or <em>y</em> > 0 (or both), otherwise 0.0</li> 383<li> <kbd>~</kbd><em>x</em>: logical NOT operator, return value 1.0 if <em>not</em> <em>x</em> > 0, otherwise 0.0</li> 384<li> <kbd>+</kbd><em>x</em>: unary plus, return 1.0*value</li> 385<li> <kbd>-</kbd><em>x</em>: unary minus, return -1.0*value</li> 386<li> <em>x</em> <kbd>?</kbd> <em>y</em> : <em>z</em>: ternary conditional expression, return value <em>y</em> if <em>x</em> != 0, otherwise <em>z</em>; only one ternary conditional permitted per statement</li> 387<li> <em>x</em> <kbd>=</kbd> <em>y</em>: assignment; assignment variables are restricted to letter combinations only (e.g. Xi not X1)</li> 388<li> <em>x</em> <kbd>;</kbd> <em>y</em>: statement separator </li> 389<li> <kbd>pi</kbd>: constant (3.141659...)</li> 390<li> <kbd>e</kbd>: constant (2.71828...)</li> 391<li> <kbd>QuantumRange</kbd>: constant maximum pixel value (255 for Q8, 65535 for Q16)</li> 392<li> <kbd>QuantumScale</kbd>: constant 1.0/<kbd>QuantumRange</kbd></li> 393<li> <kbd>intensity</kbd>: pixel intensity; equivalent to 0.299*red+0.587*green+0.114*blue</li> 394<li> <kbd>hue</kbd>: pixel hue</li> 395<li> <kbd>saturation</kbd>: pixel saturation</li> 396<li> <kbd>lightness</kbd>: pixel lightness; equivalent to 0.5*max(red,green,blue) + 0.5*min(red,green,blue)</li> 397<li> <kbd>luminance</kbd>: pixel luminance; equivalent to 0.2126*red + 0.7152*green + 0.0722*blue</li> 398<li> <kbd>red, green, blue</kbd>, etc.: color names</li> 399<li> <kbd>#ccc, #cbfed0, #b9e1cc00</kbd>, etc.: color hex values</li> 400<li> <kbd>rgb(), rgba(), cmyk(), cmyka(), hsl(), hsla()</kbd>: color functions</li> 401<li> <kbd>s, t, u, v, n, i, j, w, h, z, r, g, b, a, o, c, y, m, k</kbd>: symbols</li> 402<li> <kbd>abs(</kbd><em>x</em><kbd>)</kbd>: absolute value function</li> 403<li> <kbd>acos(</kbd><em>x</em><kbd>)</kbd>: arc cosine function</li> 404<li> <kbd>airy(</kbd><em>x</em><kbd>)</kbd>: Airy function (max=1, min=0); <kbd>airy(</kbd><em>x</em><kbd>)</kbd>=<kbd>[jinc(</kbd><em>x</em><kbd>)]<sup>2</sup></kbd>=<kbd>[2*j1(</kbd><em>pi*x</em><kbd>)/(</kbd><em>pi*x</em><kbd>)]<sup>2</sup></kbd></li> 405<li> <kbd>alt(</kbd><em>x</em><kbd>)</kbd>: sign alternation function (return 1.0 if <kbd>int(</kbd><em>x</em><kbd>)</kbd> is even, -1.0 if <kbd>int(</kbd><em>x</em><kbd>)</kbd> is odd)</li> 406<li> <kbd>asin(</kbd><em>x</em><kbd>)</kbd>: arc sine function</li> 407<li> <kbd>atan(</kbd><em>x</em><kbd>)</kbd>: arc tangent function</li> 408<li> <kbd>atan2(</kbd><em>y</em>,<em>x</em><kbd>)</kbd>: arc tangent function of two variables</li> 409<li> <kbd>ceil(</kbd><em>x</em><kbd>)</kbd>: smallest integral value not less than argument</li> 410<li> <kbd>channel(</kbd><em>r</em>,<em>g</em>,<em>b</em>,<em>a</em><kbd>)</kbd>: select numeric argument based on current channel</li> 411<li> <kbd>channel(</kbd><em>c</em>,<em>m</em>,<em>y</em>,<em>k</em>,<em>a</em><kbd>)</kbd>: select numeric argument based on current channel</li> 412<li> <kbd>cos(</kbd><em>x</em><kbd>)</kbd>: cosine function</li> 413<li> <kbd>cosh(</kbd><em>x</em><kbd>)</kbd>: hyperbolic cosine function</li> 414<li> <kbd>debug(</kbd><em>x</em><kbd>)</kbd>: print <em>x</em> (useful for debugging your expression)</li> 415<li> <kbd>exp(</kbd><em>x</em><kbd>)</kbd>: natural exponential function (<em>e<sup>x</sup></em>)</li> 416<li> <kbd>floor(</kbd><em>x</em><kbd>)</kbd>: largest integral value not greater than argument</li> 417<li> <kbd>hypot(</kbd><em>x</em>,<em>y</em><kbd>)</kbd>: the square root of x<sup>2</sup>+y<sup>2</sup></li> 418<li> <kbd>int(</kbd><em>x</em><kbd>)</kbd>: greatest integer function (return greatest integer less than or equal to <em>x</em>)</li> 419<li> <kbd>j0(</kbd><em>x</em><kbd>)</kbd>: Bessel functions of <em>x</em> of the first kind of order 0</li> 420<li> <kbd>j1(</kbd><em>x</em><kbd>)</kbd>: Bessel functions of <em>x</em> of the first kind of order 1</li> 421<li> <kbd>jinc(</kbd><em>x</em><kbd>)</kbd>: jinc function (max=1, min=-0.1323); <kbd>jinc(</kbd><em>x</em><kbd>)</kbd>=<kbd>2*j1(</kbd><em>pi*x</em><kbd>)/(</kbd><em>pi*x</em><kbd>)</kbd></li> 422<li> <kbd>ln(</kbd><em>x</em><kbd>)</kbd>: natural logarithm function</li> 423<li> <kbd>log(</kbd><em>x</em><kbd>)</kbd>: logarithm base 10</li> 424<li> <kbd>logtwo(</kbd><em>x</em><kbd>)</kbd>: logarithm base 2</li> 425<li> <kbd>ln(</kbd><em>x</em><kbd>)</kbd>: natural logarithm</li> 426<li> <kbd>max(</kbd><em>x</em>, <em>y</em><kbd>)</kbd>: maximum of <em>x</em> and <em>y</em></li> 427<li> <kbd>min(</kbd><em>x</em>, <em>y</em><kbd>)</kbd>: minimum of <em>x</em> and <em>y</em></li> 428<li> <kbd>mod(</kbd><em>x</em>, <em>y</em><kbd>)</kbd>: floating-point remainder function</li> 429<li> <kbd>pow(</kbd><em>x</em>,<em>y</em><kbd>)</kbd>: power function (<em>x<sup>y</sup></em>)</li> 430<li> <kbd>rand()</kbd>: value uniformly distributed over the interval [0.0, 1.0) with a 2 to the 128th-1 period</li> 431<li> <kbd>round()</kbd>: round to integral value, regardless of rounding direction</li> 432<li> <kbd>sign(</kbd><em>x</em><kbd>)</kbd>: return -1.0 if <em>x</em> is less than 0.0 otherwise 1.0</li> 433<li> <kbd>sin(</kbd><em>x</em><kbd>)</kbd>: sine function</li> 434<li> <kbd>sinc(</kbd><em>x</em><kbd>)</kbd>: sinc function (max=1, min=-0.21); <kbd>sinc(</kbd><em>x</em><kbd>)</kbd>=<kbd>sin(</kbd><em>pi*x</em><kbd>)/(</kbd><em>pi*x</em><kbd>)</kbd></li> 435<li> <kbd>sinh(</kbd><em>x</em><kbd>)</kbd>: hyperbolic sine function</li> 436<li> <kbd>sqrt(</kbd><em>x</em><kbd>)</kbd>: square root function</li> 437<li> <kbd>tan(</kbd><em>x</em><kbd>)</kbd>: tangent function</li> 438<li> <kbd>tanh(</kbd><em>x</em><kbd>)</kbd>: hyperbolic tangent function</li> 439<li> <kbd>trunc(</kbd><em>x</em><kbd>)</kbd>: round to integer, towards zero</li> 440</ul> 441 442<p>The expression semantics include these rules:</p> 443 444<ul> 445<li>symbols are case insensitive</li> 446<li>only one ternary conditional (e.g. x ? y : z) per statement</li> 447<li>statements are assignments or the final expression to return</li> 448<li>an assignment starts a statement, it is not an operator</li> 449<li>assignments to built-ins do not throw an exception and have no effect; e.g. <kbd>r=3.0; r</kbd> returns the pixel red color value, not 3.0</li> 450<li>Unary operators have a lower priority than binary operators, that is, the unary minus (negation) has lower precedence than exponentiation, so -3^2 is interpreted as -(3^2) = -9. Use parentheses to clarify your intent (e.g. (-3)^2 = 9).</li> 451<li>Similarly, care must be exercised when using the slash ('/') symbol. The string of characters <em>1/2x</em> is interpreted as (1/2)x. The contrary interpretation should be written explicitly as 1/(2x). Again, the use of parentheses helps clarify the meaning and should be used whenever there is any chance of misinterpretation.</li> 452</ul> 453 454 455</div> 456 457<h3>Source Images</h3> 458<div class="doc-section"> 459 460<p>The symbols <kbd>u</kbd> and <kbd>v</kbd> refer to the first and second images, respectively, in the current image sequence. Refer to a particular image in a sequence by appending its index to any image reference (usually <kbd>u</kbd>), with a zero index for the beginning of the sequence. A negative index counts from the end. For example, <kbd>u[0]</kbd> is the first image in the sequence, <kbd>u[2]</kbd> is the third, <kbd>u[-1]</kbd> is the last image, and <kbd>u[t]</kbd> is the current image. The current image can also be referenced by <kbd>s</kbd>. If the sequence number exceeds the length of the sequence, the count is wrapped. Thus in a 3-image sequence, <kbd>u[-1]</kbd>, <kbd>u[2]</kbd>, and <kbd>u[5]</kbd> all refer to the same (third) image.</p> 461 462<p>As an example, we form an image by averaging the first image and third images:</p> 463 464<p class='crt'><span class="crtprompt"> $magick> </span><span class='crtin'>convert image1.jpg image2.jpg image3.jpg -fx "(u+u[2])/2.0" image.jpg</span></p> 465<p>By default, the image to which <kbd>p</kbd>, <kbd>r</kbd>, <kbd>g</kbd>, <kbd>b</kbd>, <kbd>a</kbd>, etc., are applied is the first image <kbd>u</kbd> in the image list, which may also be referenced using <kbd>s</kbd>. </p> 466 467<p>It is important to note the special role played by the first image. This is the only image in the image sequence that is modified, other images are used only for their data. As an illustrative example, consider the following, and note that the setting <a href="/www/command-line-options.html#channel">-channel red</a> instructs <a href="/www/command-line-options.html#fx">-fx</a> to modify only the red channel; nothing in the green or blue channels will change. It is instructive to ponder why the result is not symmetric.</p> 468 469<p class='crt'><span class="crtprompt"> $magick> </span><span class='crtin'>convert -channel red logo: -flop logo: -resize "20%" -fx "(u+v)/2" image.jpg</span></p> 470<div class="image"> 471 <a href="/images/logo-sm-flop.png"><img src="/images/logo-sm-flop.png" width="128" height="96" alt="logo-sm-flop.png" /></a> 472 <a href="/images/logo-sm.png"><img src="/images/logo-sm.png" width="128" height="96" alt="logo-sm.png" /></a> 473<img style="margin-top:38px; margin-bottom:38px;" src="/images/right.gif" width="20" height="20" alt="==>" /> 474 <a href="/images/logo-sm-fx.png"><img src="/images/logo-sm-fx.png" width="128" height="96" alt="logo-sm-fx.png" /></a> 475</div> 476 477 478</div> 479 480<h3>Accessing Pixels</h3> 481<div class="doc-section"> 482 483<p>All color values are normalized to the range of 0.0 to 1.0. The alpha channel ranges from 0.0 (fully transparent) to 1.0 (fully opaque).</p> 484 485<p>The pixels are processed one at a time, but a different pixel of an image can be specified using a pixel index represented by <kbd>p</kbd>. For example,</p> 486 487<pre class="text"> 488 p[-1].g green value of pixel to the immediate left of the current pixel 489 p[-1,-1].r red value of the pixel diagonally left and up from current pixel 490</pre> 491 492<p>To specify an absolute position, use braces, rather than brackets.</p> 493 494<pre class="text"> 495 p{0,0}.r red value of the pixel in the upper left corner of the image 496 p{12,34}.b blue pixel value at column number 12, row 34 of the image 497</pre> 498 499<p>Integer values of the position retrieve the color of the pixel referenced, while non-integer position values return a blended color according to the current <a href="/www/command-line-options.html#interpolate">-interpolate</a> setting.</p> 500 501<p>A position outside the boundary of the image retrieves a value dictated by the <a href="/www/command-line-options.html#virtual-pixel">-virtual-pixel</a> option setting.</p> 502 503</div> 504 505<h3>Apply an Expression to Select Image Channels</h3> 506<div class="doc-section"> 507 508<p>Use the <a href="/www/command-line-options.html#channel">-channel</a> setting to specify the output channel of the result. If no output channel is given, the result is set over all channels except the opacity channel. For example, to replace the red channel of <kbd>alpha.png</kbd> with the average of the green channels from the images <kbd>alpha.png</kbd> and <kbd>beta.png</kbd>, use:</p> 509 510<p class='crt'><span class="crtprompt"> $magick> </span><span class='crtin'>convert alpha.png beta.png -channel red -fx "(u.g+v.g)/2" gamma.png</span></p> 511</div> 512 513<h3>Results</h3> 514<div class="doc-section"> 515 516<p>The <a href="/www/command-line-options.html#fx">-fx</a> operator evaluates the given expression for each channel (set by <a href="/www/command-line-options.html#channel">-channel</a>) of each pixel in the first image (<kbd>u</kbd>) in the sequence. The computed values are temporarily stored in a copy (clone) of that first image until all the pixels have been processed, after which this single new image replaces the list of images in the current image sequence. As such, in the previous example the updated version of <kbd>alpha.png</kbd> replaces both of the original images, <kbd>alpha.png</kbd> and <kbd>beta.png</kbd>, before being saved as <kbd>gamma.png</kbd>.</p> 517 518<p>The current image <kbd>s</kbd> is set to the first image in the sequence (<kbd>u</kbd>), and <kbd>t</kbd> to its index, 0. The symbols <kbd>i</kbd> and <kbd>j</kbd> reference the current pixel being processed.</p> 519 520 521<p>For use with <a href="/www/command-line-options.html#format_identify_">-format</a>, the value-escape <kbd>%[fx: ]</kbd> is evaluated just once for each image in the current image sequence. As each image in the sequence is being evaluated, <kbd>s</kbd> and <kbd>t</kbd> successively refer to the current image and its index, while <kbd>i</kbd> and <kbd>j</kbd> are set to zero, and the current channel set to red (<a href="/www/command-line-options.html#channel">-channel</a> is ignored). An example:</p> 522 523<p class='crt'><span class="crtprompt"> $magick> </span><span class='crtin'>convert canvas:'rgb(25%,50%,75%)' rose: -colorspace rgb \ <br/> 524 -format 'Red channel of NW corner of image #%[fx:t] is %[fx: s]' info:</span><span class='crtout'>Red channel of NW corner of image #0 is 0.453758 <br/> 525 Red channel of NW corner of image #1 is 0.184588</span></p> 526<p>Here we use the image indexes to <em>rotate</em> each image differently, and use <kbd>-set</kbd> with the image index to set a different <em>pause delay</em> on the first image in the animation:</p> 527 528<p class='crt'><span class="crtprompt"> $magick> </span><span class='crtin'>convert rose: -duplicate 29 -virtual-pixel Gray -distort SRT '%[fx:360.0*t/n]' \ <br /> 529 -set delay '%[fx:t == 0 ? 240 : 10]' -loop 0 rose.gif</span></p><p>The color-escape <kbd>%[pixel: ]</kbd> is evaluated once per image and per color channel in that image (<a href="/www/command-line-options.html#channel">-channel</a> is ignored), The values generated are then converted into a color string (a named color or hex color value). The symbols <kbd>i</kbd> and <kbd>j</kbd> are set to zero, and <kbd>s</kbd> and <kbd>t</kbd> refer to each successively current image and index.</p> 530 531</div> 532</div> 533 534</div> 535 536<div id="linkbar"> 537 <span id="linkbar-west"> </span> 538 <span id="linkbar-center"> 539 <a href="http://www.imagemagick.org/discourse-server/">Discourse Server</a> • 540 <a href="http://www.imagemagick.org/MagickStudio/scripts/MagickStudio.cgi">Studio</a> 541 </span> 542 <span id="linkbar-east"> </span> 543 </div> 544 <div class="footer"> 545 <span id="footer-west">© 1999-2011 ImageMagick Studio LLC</span> 546 <span id="footer-east"> <a href="http://www.imagemagick.org/script/contact.php">Contact the Wizards</a></span> 547 </div> 548 <div style="clear: both; margin: 0; width: 100%; "></div> 549 <script type="text/javascript"> 550 var _gaq = _gaq || []; 551 _gaq.push(['_setAccount', 'UA-17690367-1']); 552 _gaq.push(['_trackPageview']); 553 554 (function() { 555 var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; 556 ga.src = ('https:' == document.location.protocol ? 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