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  26 <h2>Vecto - Simple Vector Drawing with Common Lisp</h2>
  27
  28 <blockquote class='abstract'>
  29 <h3>Abstract</h3>
  30
  31 <p>Vecto is a simplified interface to the
  32 powerful <a href="http://projects.tuxee.net/cl-vectors/">CL-VECTORS</a>
  33 vector rasterization library. It presents a function-oriented
  34 interface similar to <a href="http://www.cliki.net/CL-PDF">CL-PDF</a>,
  35 but the results can be saved to a PNG instead of a PDF file. Since
  36 Vecto and all supporting libraries are written completely in Common
  37 Lisp, without depending on external non-Lisp libraries, it should work
  38 in any Common Lisp environment. Vecto is available under a BSD-like
  39 license.
  40
  41 The latest version is 1.6, released on December 30th, 2021.
  42
  43 <p>Vecto is used
  44   by <a href="http://wigflip.com/easystreet/">Easystreet</a>
  45   and <a href='http://www.xach.com/moviecharts/'>Movie Charts</a>.
  46
  47 <p>The canonical location for Vecto
  48 is <a href="http://www.xach.com/lisp/vecto/">http://www.xach.com/lisp/vecto/</a>.
  49
  50 <p class='download'>Download shortcut:</p>
  51
  52 <p><a href="http://www.xach.com/lisp/vecto.tgz">http://www.xach.com/lisp/vecto.tgz</a>
  53
  54 </blockquote>
  55
  56 <h3>Contents</h3>
  57
  58 <ol>
  59 <li> <a href='#sect-overview-and-limitations'>Overview and Limitations</a>
  60 <li> <a href='#sect-examples'>Examples</a>
  61 <li> <a href='#sect-dictionary'>Dictionary</a>
  62
  63 <ul>
  64   <li> <a href='#sect-canvases'>Canvases</a>
  65     <ul>
  66       <li> <a href='#with-canvas'><tt>with-canvas</tt></a>
  67       <li> <a href='#clear-canvas'><tt>clear-canvas</tt></a>
  68       <li> <a href='#compose'><tt>compose</tt></a>
  69       <li> <a href='#save-png'><tt>save-png</tt></a>
  70       <li> <a href='#save-png-stream'><tt>save-png-stream</tt></a>
  71     </ul>
  72
  73   <li> <a href='#sect-graphics-state'>Graphics State</a>
  74     <ul>
  75       <li> <a href='#with-graphics-state'><tt>with-graphics-state</tt></a>
  76       <li> <a href='#set-rgba-fill'><tt>set-rgba-fill</tt></a>
  77       <li> <a href='#set-rgba-fill'><tt>set-rgb-fill</tt></a>
  78       <li> <a href='#set-gradient-fill'><tt>set-gradient-fill</tt></a>
  79       <li> <a href='#set-rgba-stroke'><tt>set-rgba-stroke</tt></a>
  80       <li> <a href='#set-rgba-stroke'><tt>set-rgb-stroke</tt></a>
  81       <li> <a href='#set-line-cap'><tt>set-line-cap</tt></a>
  82       <li> <a href='#set-line-join'><tt>set-line-join</tt></a>
  83       <li> <a href='#set-line-width'><tt>set-line-width</tt></a>
  84       <li> <a href='#set-dash-pattern'><tt>set-dash-pattern</tt></a>
  85       <li> <a href='#translate'><tt>translate</tt></a>
  86       <li> <a href='#rotate'><tt>rotate</tt></a>
  87       <li> <a href='#scale'><tt>scale</tt></a>
  88       <li> <a href='#skew'><tt>skew</tt></a>
  89       <li> <a href='#clip-path'><tt>clip-path</tt></a>
  90       <li> <a href='#even-odd-clip-path'><tt>even-odd-clip-path</tt></a>
  91     </ul>
  92
  93   <li> <a href='#sect-paths'>Paths</a>
  94     <ul>
  95       <li> <a href='#move-to'><tt>move-to</tt></a>
  96       <li> <a href='#line-to'><tt>line-to</tt></a>
  97       <li> <a href='#curve-to'><tt>curve-to</tt></a>
  98       <li> <a href='#quadratic-to'><tt>quadratic-to</tt></a>
  99       <li> <a href='#arc'><tt>arc</tt></a>
 100       <li> <a href='#arcn'><tt>arcn</tt></a>
 101       <li> <a href='#ellipse-arc'><tt>ellipse-arc</tt></a>
 102       <li> <a href='#ellipse-arcn'><tt>ellipse-arcn</tt></a>
 103       <li> <a href='#close-subpath'><tt>close-subpath</tt></a>
 104       <li> <a href='#stroke-to-paths'><tt>stroke-to-paths</tt></a>
 105       <li> <a href='#rectangle'><tt>rectangle</tt></a>
 106       <li> <a href='#rounded-rectangle'><tt>rounded-rectangle</tt></a>
 107       <li> <a href='#centered-ellipse-path'><tt>centered-ellipse-path</tt></a>
 108       <li> <a href='#centered-circle-path'><tt>centered-circle-path</tt></a>
 109     </ul>
 110
 111   <li> <a href='#sect-painting'>Painting</a>
 112     <ul>
 113       <li> <a href='#fill-path'><tt>fill-path</tt></a>
 114       <li> <a href='#even-odd-fill'><tt>even-odd-fill</tt></a>
 115       <li> <a href='#stroke'><tt>stroke</tt></a>
 116       <li> <a href='#fill-and-stroke'><tt>fill-and-stroke</tt></a>
 117       <li> <a href='#even-odd-fill-and-stroke'><tt>even-odd-fill-and-stroke</tt></a>
 118       <li> <a href='#end-path-no-op'><tt>end-path-no-op</tt></a>
 119     </ul>
 120
 121   <li> <a href='#sect-text'>Text</a>
 122     <ul>
 123       <li> <a href='#get-font'><tt>get-font</tt></a>
 124       <li> <a href='#set-font'><tt>set-font</tt></a>
 125       <li> <a href='#set-character-spacing'><tt>set-character-spacing</tt></a>
 126       <li> <a href='#*default-character-spacing*'><tt>*default-character-spacing*</tt></a>
 127       <li> <a href='#draw-string'><tt>draw-string</tt></a>
 128       <li> <a href='#string-paths'><tt>string-paths</tt></a>
 129       <li> <a href='#draw-centered-string'><tt>draw-centered-string</tt></a>
 130       <li> <a href='#centered-string-paths'><tt>centered-string-paths</tt></a>
 131       <li> <a href='#string-bounding-box'><tt>string-bounding-box</tt></a>
 132     </ul>
 133
 134   <li> <a href='#sect-miscellaneous'>Miscellaneous</a>
 135     <ul>
 136       <li> <a href='#const-kappa'><tt>+kappa+</tt></a>
 137     </ul>
 138
 139 </ul>
 140
 141 <li> <a href='#sect-references'>References</a>
 142 <li> <a href='#sect-acknowledgements'>Acknowledgements</a>
 143 <li> <a href='#sect-feedback'>Feedback</a>
 144
 145 </ol>
 146
 147 <a name='sect-overview-and-limitations'><h3>Overview and Limitations</h3></a>
 148
 149 <p>Vecto is a library that provides a simple interface to the
 150 the <a href="http://projects.tuxee.net/cl-vectors/">CL-VECTORS</a>
 151 vector drawing library. It supports drawing on a canvas and saving the
 152 results to a PNG file.
 153
 154 <p>Vecto depends on the following libraries:
 155
 156 <ul>
 157 <li> <a href="http://projects.tuxee.net/cl-vectors/">CL-VECTORS</a>
 158 <li> <a href="http://www.xach.com/lisp/zpb-ttf/">ZPB-TTF</a>
 159 <li> <a href="http://www.xach.com/lisp/salza2/">Salza2</a>
 160 <li> <a href="http://www.xach.com/lisp/zpng/">ZPNG</a>
 161 </ul>
 162
 163 <p>The easiest way to install Vecto and all its dependencies is
 164 with <a href="http://www.quicklisp.org/">Quicklisp</a>.
 165
 166 <p>Vecto's function interface is similar to the
 167 PDF vector description and painting interface: you create images by
 168 describing vector paths, then using stroke or fill operations to paint
 169 to the canvas.
 170
 171 <p>Vecto's color system uses red, green, blue, and alpha color
 172 components for drawing. The results can be be saved to a PNG with an
 173 alpha channel.
 174
 175 <p>Vecto's coordinate system starts at the lower-left corner of the
 176 image, and increases rightwards along the X axis and upwards along the
 177 Y axis.
 178
 179 <p>All measurements are in pixels.
 180
 181 <p>PDF is a feature-rich system. Vecto supports a small subset of
 182 PDF-style operations. In particular, it does not support:
 183
 184 <ul>
 185 <li> sampled images
 186 <li> pattern or functional fill
 187 <li> complex layout of text
 188 <li> PostScript fonts
 189 <li> non-RGB color spaces
 190 </ul>
 191
 192 <p>Other limitations:
 193
 194 <ul>
 195 <li> No output formats other than 8-bit, truecolor-alpha PNGs
 196 <li> No access to underlying pixel data
 197 </ul>
 198
 199 <p>Related libraries:
 200
 201 <ul>
 202   <li> <a href="http://common-lisp.net/project/imago/">Imago</a>
 203
 204   <li> <a href="http://cyrusharmon.org/projects?project=ch-image">ch-image</a>
 205
 206   <li> <a href="http://ygingras.net/poly-pen">Poly-pen</a>
 207 </ul>
 208
 209
 210 <a name='sect-examples'><h3>Examples</h3></a>
 211
 212 <p>All examples are available in <tt>doc/examples.lisp</tt> in the Vecto
 213 distribution. That file starts with:
 214
 215 <pre>
 216 (defpackage #:vecto-examples
 217   (:use #:cl #:vecto))
 218
 219 (in-package #:vecto-examples)
 220 </pre>
 221
 222
 223 <pre>
 224 <img border=0 align=right src='lambda-example.png'
 225 >(defun radiant-lambda (file)
 226   (<a href='#with-canvas'>with-canvas</a> (:width 90 :height 90)
 227     (let ((font (<a href='#get-font'>get-font</a> "times.ttf"))
 228           (step (/ pi 7)))
 229       (<a href='#set-font'>set-font</a> font 40)
 230       (<a href='#translate'>translate</a> 45 45)
 231       (<a href='#draw-centered-string'>draw-centered-string</a> 0 -10 #(#x3BB))
 232       (<a href='#set-rgba-stroke'>set-rgb-stroke</a> 1 0 0)
 233       (<a href='#centered-circle-path'>centered-circle-path</a> 0 0 35)
 234       (<a href='#stroke'>stroke</a>)
 235       (<a href='#set-rgba-stroke'>set-rgba-stroke</a> 0 0 1.0 0.5)
 236       (<a href='#set-line-width'>set-line-width</a> 4)
 237       (dotimes (i 14)
 238         (<a href='#with-graphics-state'>with-graphics-state</a>
 239           (<a href='#rotate'>rotate</a> (* i step))
 240           (<a href='#move-to'>move-to</a> 30 0)
 241           (<a href='#line-to'>line-to</a> 40 0)
 242           (stroke)))
 243       (<a href='#save-png'>save-png</a> file))))
 244 </pre>
 245
 246 <pre>
 247 <img align=right src='feedlike-icon.png'
 248 >(defun feedlike-icon (file)
 249   (with-canvas (:width 100 :height 100)
 250     (set-rgb-fill 1.0 0.65 0.3)
 251     (<a href='#rounded-rectangle'>rounded-rectangle</a> 0 0 100 100 10 10)
 252     (<a href='#fill-path'>fill-path</a>)
 253     (set-rgb-fill 1.0 1.0 1.0)
 254     (centered-circle-path 20 20 10)
 255     (fill-path)
 256     (flet ((quarter-circle (x y radius)
 257              (move-to (+ x radius) y)
 258              (<a href='#arc'>arc</a> x y radius 0 (/ pi 2))))
 259       (set-rgb-stroke 1.0 1.0 1.0)
 260       (set-line-width 15)
 261       (quarter-circle 20 20 30)
 262       (stroke)
 263       (quarter-circle 20 20 60)
 264       (stroke))
 265     (rounded-rectangle 5 5 90 90 7 7)
 266     (<a href='#set-gradient-fill'>set-gradient-fill</a> 50 90
 267                        1.0 1.0 1.0 0.7
 268                        50 20
 269                        1.0 1.0 1.0 0.0)
 270     (set-line-width 2)
 271     (set-rgba-stroke 1.0 1.0 1.0 0.1)
 272     (<a href='#fill-and-stroke'>fill-and-stroke</a>)
 273     (save-png file)))
 274 </pre>
 275
 276 <pre><div style='float: right' class='transparent'><img src='star-clipping.png'
 277 ></div>(defun star-clipping (file)
 278   (with-canvas (:width 200 :height 200)
 279     (let ((size 100)
 280           (angle 0)
 281           (step (* 2 (/ (* pi 2) 5))))
 282       (translate size size)
 283       (move-to 0 size)
 284       (dotimes (i 5)
 285         (setf angle (+ angle step))
 286         (line-to (* (sin angle) size)
 287                  (* (cos angle) size)))
 288       (<a href='#even-odd-clip-path'><tt>even-odd-clip-path</tt></a>)
 289       (<a href='#end-path-no-op'><tt>end-path-no-op</tt></a>)
 290       (flet ((circle (distance)
 291                (<a href='#set-rgba-fill'><tt>set-rgba-fill</tt></a> distance 0 0
 292                               (- 1.0 distance))
 293                (centered-circle-path 0 0 (* size distance))
 294                (fill-path)))
 295         (loop for i downfrom 1.0 by 0.05
 296               repeat 20 do
 297               (circle i)))
 298       (save-png file))))
 299 </pre>
 300
 301 <a name='sect-dictionary'><h3>Dictionary</h3></a>
 302
 303 <p>The following symbols are exported from the <tt>VECTO</tt> package.
 304
 305 <a name='sect-canvases'><h4>Canvases</h4></a>
 306
 307 <p><a name='with-canvas'>[Macro]</a><br>
 308 <b>with-canvas</b> (<tt>&amp;key</tt> <i>width</i> <i>height</i>)
 309 <tt>&amp;body</tt> <i>body</i>
 310
 311 <blockquote>
 312 Evaluates <i>body</i> with a canvas established with the specified
 313 dimensions as the target for drawing commands. The canvas is initially
 314 completely clear (all pixels have 0 alpha).
 315 </blockquote>
 316
 317
 318 <p><a name='clear-canvas'>[Function]</a><br>
 319 <b>clear-canvas</b> => |
 320
 321 <blockquote>
 322 Completely fills the canvas with the current fill color. Any marks on
 323 the canvas are cleared.
 324 </blockquote>
 325
 326
 327 <p><a name='save-png'>[Generic Function]</a><br>
 328 <b>compose</b> <i>layer</i> <i>x</i> <i>y</i> => |
 329
 330 <blockquote>
 331 Performs image composition by superimposing <i>image</i> on top of the
 332 current canvas, starting from the lower-left corner of the image.
 333
 334 <b>This composition disregards all transformations done to the image's
 335 coordinate system, such as translations, skewing, rotations, etc..</b>
 336 Use systems that manipulate raster graphics (such as
 337 <a href='https://common-lisp.net/project/imago/'>Imago</a>) to adjust
 338 the raster image before compositing it with Vecto.
 339
 340 This GF has no default implementations and is meant to be implemented
 341 by users.
 342 </blockquote>
 343
 344
 345 <p><a name='save-png'>[Function]</a><br>
 346 <b>save-png</b> <i>file</i> => <i>truename</i>
 347
 348 <blockquote>
 349 Writes the contents of the canvas as the PNG <i>file</i>, and returns
 350 the truename of <i>file</i>.
 351 </blockquote>
 352
 353
 354 <p><a name='save-png-stream'>[Function]</a><br>
 355 <b>save-png-stream</b> <i>stream</i> => |
 356
 357 <blockquote>
 358 Writes the contents of the canvas as a PNG to <i>stream</i>, which
 359 must accept <tt>(unsigned-byte&nbsp;8)</tt> data.
 360 </blockquote>
 361
 362
 363 <a name='sect-graphics-state'><h4>Graphics State</h4></a>
 364
 365 <p>The graphics state stores several parameters used for graphic
 366 operations.
 367
 368 <p><a name='with-graphics-state'>[Macro]</a><br>
 369 <b>with-graphics-state</b> <tt>&amp;body</tt> <i>body</i>
 370
 371 <blockquote>
 372 Evaluates the forms of <i>body</i> with a copy of the current graphics
 373 state. Any modifications to the state are undone at the end of the
 374 form.
 375 </blockquote>
 376
 377
 378 <p><a name='set-rgba-fill'>[Functions]</a><br>
 379 <b>set-rgba-fill</b> <i>r</i> <i>g</i> <i>b</i> <i>alpha</i> => |<br>
 380 <b>set-rgb-fill</b> <i>r</i> <i>g</i> <i>b</i> => |
 381
 382 <blockquote>
 383 Sets the fill color. <i>r</i>, <i>g</i>, <i>b</i>, and <i>alpha</i>
 384 should be in the range of 0.0 to 1.0.
 385
 386 <p><tt>set-rgb-fill</tt> is the same as <tt>set-rgba-fill</tt> with an
 387 implicit alpha value of 1.0.
 388
 389 <p>The fill color is used
 390 for <a
 391 href='#clear-canvas'><tt>CLEAR-CANVAS</tt></a>, <a
 392 href='#fill-path'><tt>FILL-PATH</tt></a>, <a
 393 href='#even-odd-fill'><tt>EVEN-ODD-FILL</tt></a>, <a
 394 href='#fill-and-stroke'><tt>FILL-AND-STROKE</tt></a>, <a
 395 href='#even-odd-fill-and-stroke'><tt>EVEN-ODD-FILL-AND-STROKE</tt></a>,
 396 and <a href='#draw-string'><tt>DRAW-STRING</tt></a>.
 397
 398 </blockquote>
 399
 400 <p><a name='set-gradient-fill'>[Function]</a><br>
 401 <b>set-gradient-fill</b>
 402 <i>x0</i> <i>y0</i> <i>r0</i> <i>g0</i> <i>b0</i> <i>a0</i>
 403 <i>x1</i> <i>y1</i> <i>r1</i> <i>g1</i> <i>b1</i> <i>a1</i>
 404 <tt>&amp;key</tt> (<i>extend-start</i> <tt>t</tt>)
 405 (<i>extend-end</i> <tt>t</tt>)
 406 (<i>domain-function</i> <tt>'linear-domain</tt>)
 407
 408 <blockquote>
 409 Set the fill color source to an axial gradient. The start point
 410 is <i>x0,y0</i> and the start color is <i>r0,g0,b0,a0</i>. The end
 411 point is <i>x1, y1</i> and the end color is <i>r1,g1,b1,a1</i>.
 412
 413 <p>Two domain functions are available:
 414
 415 <ul>
 416
 417 <li> <tt>LINEAR-DOMAIN</tt>, the default, makes a transition from the
 418 start color to the end color along the axis between the start and end
 419 points
 420
 421 <li> <tt>BILINEAR-DOMAIN</tt> makes a transition from the start color
 422 to the end color from the start point to the midpoint, then back to
 423 the start color from the midpoint to the end point
 424 </ul>
 425
 426
 427 <p>Two coordinate functions are available:
 428
 429 <ul>
 430
 431 <li> <tt>CARTESIAN-COORDINATES</tt>, the default, creates a linear
 432 gradient.
 433
 434 <li> <tt>POLAR-COORDINATES</tt> creates a radial gradient with the
 435 start point denoting the start of the circle and the end point
 436 denoting the ending circle.
 437 </ul>
 438
 439
 440 <pre><img style='float: right' class='transparent'
 441  src='linear-gradient.png'>(defun gradient-example (file)
 442   (with-canvas (:width 200 :height 50)
 443     (set-gradient-fill 25 0
 444                        1 0 0 1
 445                        175 0
 446                        1 0 0 0)
 447     (rectangle 0 0 200 50)
 448     (fill-path)
 449     (save-png file)))
 450 </pre>
 451
 452 <pre><img style='float: right' class='transparent'
 453  src='bilinear-gradient.png'>(defun gradient-bilinear-example (file)
 454   (with-canvas (:width 200 :height 50)
 455     (set-gradient-fill 25 0
 456                        1 0 0 1
 457                        175 0
 458                        1 0 0 0
 459                        :domain-function 'bilinear-domain)
 460     (rectangle 0 0 200 50)
 461     (fill-path)
 462     (save-png file)))
 463 </pre>
 464
 465 <p>
 466
 467 </blockquote>
 468
 469 <p><a name='set-rgba-stroke'>[Functions]</a><br>
 470 <b>set-rgba-stroke</b> <i>r</i> <i>g</i> <i>b</i> <i>alpha</i> => |<br>
 471 <b>set-rgb-stroke</b> <i>r</i> <i>g</i> <i>b</i> => |
 472
 473 <blockquote>
 474 Sets the stroke color. <i>r</i>, <i>g</i>, <i>b</i>, and <i>alpha</i>
 475 should be in the range of 0.0 to 1.0.
 476
 477 <p><tt>set-rgb-stroke</tt> is the same as <tt>set-rgba-stroke</tt>
 478 with an implicit alpha value of 1.0.
 479
 480 <p>The stroke color is used for <a href='#stroke'><tt>STROKE</tt></a>,
 481 <a href='#fill-and-stroke'><tt>FILL-AND-STROKE</tt></a>,
 482 and <a href='#even-odd-fill-and-stroke'><tt>EVEN-ODD-FILL-AND-STROKE</tt></a>.
 483 </blockquote>
 484
 485
 486 <p><a name='set-line-cap'>[Function]</a><br>
 487 <b>set-line-cap</b> <i>style</i> => |
 488
 489 <blockquote>
 490 Sets the line cap style to <i>style</i>, which must be one
 491 of <tt>:BUTT</tt>, <tt>:SQUARE</tt>, or <tt>:ROUND</tt>. The initial
 492 value is <tt>:BUTT</tt>.
 493
 494 <p><table cellspacing=5 id="line-cap">
 495 <tr>
 496  <td align=center><img src="cap-style-butt.png"></td>
 497  <td align=center><img src="cap-style-square.png"></td>
 498  <td align=center><img src="cap-style-round.png"></td>
 499 </tr>
 500 <tr>
 501  <td align=center><tt>:BUTT</tt></td>
 502  <td align=center><tt>:SQUARE</tt></td>
 503  <td align=center><tt>:ROUND</tt></td>
 504 </tr>
 505 </table>
 506
 507 </blockquote>
 508
 509
 510 <p><a name='set-line-join'>[Function]</a><br>
 511 <b>set-line-join</b> <i>style</i> => |
 512
 513 <blockquote>
 514 Sets the line join style to <i>style</i>, which must be one
 515 of <tt>:MITER</tt>, <tt>:BEVEL</tt>, or <tt>:ROUND</tt>. The initial
 516 value is <tt>:MITER</tt>.
 517
 518 <p><table cellspacing=5 id="line-join">
 519 <tr>
 520  <td align=center><img src="join-style-miter.png"></td>
 521  <td align=center><img src="join-style-bevel.png"></td>
 522  <td align=center><img src="join-style-round.png"></td>
 523 </tr>
 524 <tr>
 525  <td align=center><tt>:MITER</tt></td>
 526  <td align=center><tt>:BEVEL</tt></td>
 527  <td align=center><tt>:ROUND</tt></td>
 528 </tr>
 529 </table>
 530
 531 </blockquote>
 532
 533
 534 <p><a name='set-line-width'>[Function]</a><br>
 535 <b>set-line-width</b> <i>width</i> => |
 536
 537 <blockquote>
 538 Sets the line width for strokes to <i>width</i>.
 539 </blockquote>
 540
 541
 542
 543 <p><a name='set-dash-pattern'>[Function]</a><br>
 544 <b>set-dash-pattern</b> <i>dash-vector</i> <i>phase</i> => |
 545
 546 <blockquote>
 547 Sets the dash pattern according to <i>dash-vector</i> and <i>phase</i>.
 548
 549 <p><i>dash-vector</i> should be a vector of numbers denoting on and
 550 off patterns for a stroke. An empty <i>dash-vector</i> is the same as
 551 having no dash pattern at all.
 552
 553 <p><i>phase</i> is how far along the dash pattern to proceed before
 554 applying the pattern to the current stroke.
 555
 556 <p>
 557 <table>
 558   <tr>
 559     <th>Appearance</th>
 560     <th>Dash Vector and Phase</th>
 561   </tr>
 562   <tr>
 563     <td align=center><img src="dash-pattern-none.png"></td>
 564     <td align=left><tt>#() 0</tt></td>
 565   </tr>
 566   <tr>
 567     <td align=center><img src="dash-pattern-a.png"></td>
 568     <td align=left><tt>#(30 30) 0</tt></td>
 569   </tr>
 570   <tr>
 571     <td align=center><img src="dash-pattern-b.png"></td>
 572     <td align=left><tt>#(30 30) 15</tt></td>
 573   </tr>
 574   <tr>
 575     <td align=center><img src="dash-pattern-c.png"></td>
 576     <td align=left><tt>#(10 20 10 40) 0</tt></td>
 577   </tr>
 578   <tr>
 579     <td align=center><img src="dash-pattern-d.png"></td>
 580     <td align=left><tt>#(10 20 10 40) 13</tt></td>
 581   </tr>
 582   <tr>
 583     <td align=center><img src="dash-pattern-e.png"></td>
 584     <td align=left><tt>#(30 30) 0</tt>, <tt>:ROUND</tt> line caps</td>
 585   </tr>
 586 </table>
 587 </blockquote>
 588
 589
 590 <p><a name='translate'>[Function]</a><br>
 591 <b>translate</b> <i>x</i> <i>y</i> => |
 592
 593 <blockquote>
 594 Offsets the coordinate system by <i>x</i> units horizontally
 595 and <i>y</i> units vertically.
 596 </blockquote>
 597
 598
 599 <p><a name='rotate'>[Function]</a><br>
 600 <b>rotate</b> <i>radians</i> => |
 601
 602 <blockquote>
 603 Rotates the coordinate system by <i>radians</i>.
 604 </blockquote>
 605
 606
 607 <p><a name='scale'>[Function]</a><br>
 608 <b>scale</b> <i>sx</i> <i>sy</i> => |
 609
 610 <blockquote>
 611 Scales the coordinate system by <i>sx</i> horizontally
 612 and <i>sy</i> vertically.
 613 </blockquote>
 614
 615
 616 <p><a name='skew'>[Function]</a><br>
 617 <b>skew</b> <i>ax</i> <i>ay</i> => |
 618
 619 <blockquote>
 620 Skews the X axis of the coordinate system by <i>ax</i> radians and the
 621 Y axis by <i>ay</i> radians.
 622 </blockquote>
 623
 624
 625 <p><a name='clip-path'>[Function]</a><br>
 626 <b>clip-path</b> => |
 627
 628 <blockquote>
 629 Defines a clipping path based on the current path. It is not applied
 630 immediately, but is created after after the painting is done in the
 631 next call to one
 632 of <a
 633 href='#fill-path'><tt>FILL-PATH</tt></a>, <a
 634 href='#even-odd-fill'><tt>EVEN-ODD-FILL</tt></a>, <a
 635 href='#fill-and-stroke'><tt>FILL-AND-STROKE</tt></a>, <a
 636 href='#even-odd-fill-and-stroke'><tt>EVEN-ODD-FILL-AND-STROKE</tt></a>,
 637 or <a href='#end-path-no-op'><tt>END-PATH-NO-OP</tt></a>.
 638
 639 <p>The clipping path initially covers the entire canvas; no clipping
 640 is done. Subsequent calls to <tt>CLIP-PATH</tt> set the clipping path
 641 to the intersection of the established clipping path and the new
 642 clipping path, and all drawing will be done within the outline of the
 643 clipping path.
 644
 645 <p>The outline of the clipping path is defined with the nonzero
 646 winding rule, as with <a href='#fill-path'><tt>FILL-PATH</tt></a>.
 647
 648 <p>There is no way to enlarge the clipping path. However, the clipping
 649 path is part of the graphics state, so changes may be localized by
 650 using <a href='#with-graphics-state'><tt>WITH-GRAPHICS-STATE</tt></a>.
 651
 652
 653 <p><table>
 654 <tr>
 655  <td><img src="clip-unclipped.png"></td>
 656  <td>A filled red rectangle, not clipped</td>
 657 </tr>
 658 <tr>
 659  <td><img src="clip-to-circle.png"></td>
 660  <td>The same rectangle drawn with a circle clipping path in effect</td>
 661 </tr>
 662 <tr>
 663  <td><img src="clip-to-rectangle.png"></td>
 664  <td>Clipped to a rounded rectangle clipping path</td>
 665 </tr>
 666 <tr>
 667  <td><img src="clip-to-both.png"></td>
 668  <td>Clipped to the intersection of the circle and rounded rectangle clipping paths</td>
 669 </tr>
 670 </table>
 671
 672
 673
 674 </blockquote>
 675
 676
 677 <p><a name='even-odd-clip-path'>[Function]</a><br>
 678 <b>even-odd-clip-path</b> => |
 679
 680 <blockquote>
 681 Like <a href='#clip-path'><tt>CLIP-PATH</tt></a>, but uses the
 682 even/odd fill rule to determine the outline of the clipping path.
 683 </blockquote>
 684
 685
 686 <a name='sect-paths'><h4>Paths</h4></a>
 687
 688 <p>Paths are used to create lines for stroking or outlines for
 689 filling. Paths consist of straight lines and curves. Paths consist of
 690 one or more subpaths.
 691
 692 <p><a name='move-to'>[Function]</a><br>
 693 <b>move-to</b> <i>x</i> <i>y</i> => |
 694
 695 <blockquote>
 696 Starts a new subpath at (<i>x</i>,<i>y</i>). <tt>move-to</tt> must be the
 697 first step of constructing a subpath.
 698 </blockquote>
 699
 700
 701 <p><a name='line-to'>[Function]</a><br>
 702 <b>line-to</b> <i>x</i> <i>y</i> => |
 703
 704 <blockquote>
 705 Appends a straight line ending at (<i>x</i>,<i>y</i>) to the
 706 current subpath.
 707 </blockquote>
 708
 709
 710 <p><a name='curve-to'>[Function]</a><br>
 711 <b>curve-to</b>
 712 <i>cx1</i> <i>cy1</i>
 713 <i>cx2</i> <i>cy2</i>
 714 <i>x</i> <i>y</i> => |
 715
 716 <blockquote>
 717 Appends a
 718 cubic <a href="http://en.wikipedia.org/wiki/B%C3%A9zier_curve">B&eacute;zier
 719 curve</a> ending at (<i>x</i>,<i>y</i>) and with control
 720 points (<i>cx1</i>,<i>cy1</i>) and (<i>cx2</i>,<i>cy2</i>) to the current
 721 subpath.
 722 </blockquote>
 723
 724
 725 <p><a name='quadratic-to'>[Function]</a><br>
 726 <b>quadratic-to</b>
 727 <i>cx</i> <i>cy</i>
 728 <i>x</i> <i>y</i> => |
 729
 730 <blockquote>
 731 Appends a quadratic B&eacute;zier curve ending at (<i>x</i>,<i>y</i>)
 732 and with the control point (<i>cx</i>,<i>cy</i>) to the current
 733 subpath.
 734 </blockquote>
 735
 736
 737 <p><a name='arc'>[Function]</a><br>
 738 <b>arc</b> <i>x</i> <i>y</i> <i>radius</i> <i>angle1</i> <i>angle2</i>
 739 => |
 740
 741 <blockquote>
 742 Appends an arc of a circle to the current path. The center of the arc is
 743 at (<i>x</i>,<i>y</i>). The arc begins at point at a
 744 distance <i>radius</i> from the center and with an angle <i>angle1</i>
 745 radians from the positive x axis, and ends at the point
 746 with <i>angle2</i> radians. If <i>angle2</i> is less
 747 than <i>angle1</i>, it is increased by increasing multiples of 2&pi;
 748 until it is greater than or equal to <i>angle1</i>.
 749
 750 <p><table cellpadding=5>
 751     <tr><td align=center><img src="arc.png"></td></tr>
 752     <tr><td><span style='color: #0f0'><i>radius</i></span>,
 753       <span style='color: #f00'><i>angle1</i></span>,
 754       <span style='color: #00f'><i>angle2</i></span></td></tr>
 755     </table>
 756
 757 <p>If there is a current point, a straight line is added from the
 758   current point to the start point of the arc. Otherwise, a new path
 759   is started.
 760
 761 <pre><img class='transparent' style='float: right' src='pie-wedge.png'
 762 >(defun pie-wedge (file)
 763   (with-canvas (:width 80 :height 60)
 764     (let ((x 0) (y 0)
 765           (radius 70)
 766           (angle1 (* (/ pi 180) 15))
 767           (angle2 (* (/ pi 180) 45)))
 768       (translate 5 5)
 769       (set-rgb-fill 1 1 1)
 770       (move-to 0 0)
 771       (arc x y radius angle1 angle2)
 772       (fill-and-stroke)
 773       (save-png file))))
 774 </pre>
 775
 776 </blockquote>
 777
 778
 779 <p><a name='arcn'>[Function]</a><br>
 780 <b>arcn</b> <i>x</i> <i>y</i> <i>radius</i> <i>angle1</i> <i>angle2</i>
 781 => |
 782
 783 <blockquote>
 784 Like <a href='#arc'><tt>ARC</tt></a>, but draws the arc clockwise
 785 instead of counterclockwise. If <i>angle2</i> is greater
 786 than <i>angle1</i>, it is decreased by increasing multiples of 2&pi;
 787 until it is less than or equal to <i>angle1</i>.
 788
 789 <pre><img class='transparent' style='float: right' src='wiper.png'
 790 >(defun wiper (file)
 791   (with-canvas (:width 70 :height 70)
 792     (let ((x 0) (y 0)
 793           (r1 40) (r2 60)
 794           (angle1 0)
 795           (angle2 (* (/ pi 180) 90)))
 796       (translate 5 5)
 797       (set-rgba-fill 1 1 1 0.75)
 798       (arc x y r1 angle1 angle2)
 799       (arcn x y r2 angle2 angle1)
 800       (fill-and-stroke)
 801       (save-png file))))
 802 </pre>
 803
 804 </blockquote>
 805
 806 <p><a name='ellipse-arc'>[Function]</a><br>
 807 <b>ellipse-arc</b> <i>cx</i> <i>cy</i> <i>radius-x</i> <i>radius-y</i>
 808 <i>rotation-angle</i> <i>angle1</i> <i>angle2</i> => |
 809
 810 <blockquote>
 811 Like <a href='#arc'><tt>ARC</TT></a>, but draws an arc from an
 812 ellipse. The arc is drawn counterclockwise.
 813 </blockquote>
 814
 815
 816 <p><a name='ellipse-arcn'>[Function]</a><br>
 817 <b>ellipse-arcn</b> <i>cx</i> <i>cy</i> <i>radius-x</i> <i>radius-y</i>
 818 <i>rotation-angle</i> <i>angle1</i> <i>angle2</i> => |
 819
 820 <blockquote>
 821 Like <a href='#ellipse-arcn'><tt>ELLIPSE-ARCN</TT></a>, but draws the
 822 arc clockwise.
 823 </blockquote>
 824
 825
 826 <p><a name='close-subpath'>[Function]</a><br>
 827 <b>close-subpath</b> => |
 828
 829 <blockquote>
 830 Closes the current subpath. If the current point is not the same as the
 831 starting point for the subpath, appends a straight line from the
 832 current point to the starting point of the current subpath.
 833
 834 <p>Subpaths with start and end points that coincidentally overlap are
 835 not the same as closed subpaths. The distinction is important when
 836 stroking:
 837
 838 <p><table cellpadding=5>
 839  <tr>
 840    <td align=center><img src="open-subpath.png"></td>
 841    <td align=center><img src="closed-subpath.png"></td>
 842  </tr>
 843  <tr>
 844    <td align=center>Open subpath</td>
 845    <td align=center>Closed subpath</td>
 846  </tr>
 847 </table>
 848
 849 <p>If the subpath is not closed, the start and points of the subpath
 850   will be drawn with the current line cap style. If the path is
 851   closed, the start and endpoints will be treated as joined and drawn
 852   with the line join style.
 853 </blockquote>
 854
 855
 856 <p><a name='stroke-to-paths'>[Function]</a><br>
 857 <b>stroke-to-paths</b> => |
 858
 859 <blockquote>
 860 Sets the current active paths to the paths that would result from
 861 outlining a <a href='#stroke'><tt>STROKE</tt></a> operation.
 862 </blockquote>
 863
 864
 865 <p><a name='rectangle'>[Function]</a><br>
 866 <b>rectangle</b> <i>x</i> <i>y</i> <i>width</i> <i>height</i> => |
 867
 868 <blockquote>
 869 Creates a rectangular subpath with the given <i>width</i>
 870 and <i>height</i> that has its lower-left corner at
 871 (<i>x</i>,<i>y</i>). It is effectively the same as:
 872
 873 <pre>
 874 (move-to x y)
 875 (line-to (+ x width) y)
 876 (line-to (+ x width) (+ y height))
 877 (line-to x (+ y height))
 878 (close-subpath)
 879 </pre>
 880 </blockquote>
 881
 882 <p><a name='rounded-rectangle'>[Function]</a><br>
 883 <b>rounded-rectangle</b> <i>x</i> <i>y</i>
 884 <i>width</i> <i>height</i> <i>rx</i> <i>ry</i> => |
 885
 886 <blockquote>
 887 Like <a href='#rectangle'><tt>RECTANGLE</tt></a>, but rounds the
 888 corners of the rectangle paths by the x radius <i>rx</i> and the y
 889 radius <i>ry</i>.
 890 </blockquote>
 891
 892 <p><a name='centered-ellipse-path'>[Function]</a><br>
 893 <b>centered-ellipse-path</b>
 894 <i>x</i> <i>y</i>
 895 <i>rx</i> <i>ry</i>
 896
 897 <blockquote>
 898 Adds a closed subpath that outlines an ellipse centered at
 899 (<i>x</i>,<i>y</i>) with an X radius of <i>rx</i> and a Y radius
 900 of <i>ry</i>.
 901 </blockquote>
 902
 903 <p><a name='centered-circle-path'>[Function]</a><br>
 904 <b>centered-circle-path</b> <i>x</i> <i>y</i> <i>radius</i> => |
 905
 906 <blockquote>
 907 Adds a closed subpath that outlines a circle centered at
 908 (<i>x</i>,<i>y</i>) with a radius of <i>radius</i>. It is effectively
 909 the same as:
 910
 911 <pre>
 912 (centered-ellipse-path x y radius radius)
 913 </pre>
 914 </blockquote>
 915
 916
 917
 918 <a name='sect-painting'><h4>Painting</h4></a>
 919
 920 <p>After a path is defined, filling, stroking, or both will use the
 921 path to apply color to the canvas. After a path has been filled or
 922 stroked, it is no longer active; it effectively disappears.
 923
 924
 925 <p><a name='fill-path'>[Function]</a><br>
 926 <b>fill-path</b> => |
 927
 928 <blockquote>
 929 Fills the current path with the fill color or gradient. If the path
 930 has not been explicitly closed
 931 with <a href='#close-subpath'><tt>CLOSE-SUBPATH</tt></a>, it is
 932 implicitly closed before filling.  The non-zero winding rule is used
 933 to determine what areas are considered inside the path.
 934 </blockquote>
 935
 936
 937 <p><a name='even-odd-fill'>[Function]</a><br>
 938 <b>even-odd-fill</b> => |
 939
 940 <blockquote>
 941 The same as <a href='#fill-path'><tt>FILL-PATH</tt></a>, but uses the
 942 even/odd rule to determine what areas are considered inside the path.
 943 </blockquote>
 944
 945
 946 <p><a name='stroke'>[Function]</a><br>
 947 <b>stroke</b> => |
 948
 949 <blockquote>
 950 Strokes the current path. The line width, stroke color, line join
 951 style, line cap style, and dash pattern and phase determine how the
 952 stroked path will appear on the canvas.
 953 </blockquote>
 954
 955
 956 <p><a name='fill-and-stroke'>[Function]</a><br>
 957 <b>fill-and-stroke</b> => |
 958
 959 <blockquote>
 960 Fills the current path, then strokes it.
 961 </blockquote>
 962
 963
 964 <p><a name='even-odd-fill-and-stroke'>[Function]</a><br>
 965 <b>even-odd-fill-and-stroke</b> => |
 966
 967 <blockquote>
 968 Fills the current path using the even/odd rule, then strokes it.
 969 </blockquote>
 970
 971
 972 <p><a name='end-path-no-op'>[Function]</a><br>
 973 <b>end-path-no-op</b> => |
 974
 975 <blockquote>
 976 Ends the current path without painting anything. If a clipping path
 977 has been specified with <a href='#clip-path'><tt>CLIP-PATH</tt></a>
 978 or <a href='#even-odd-clip-path'><tt>EVEN-ODD-CLIP-PATH</tt></a>, it
 979 will be created by <tt>end-path-no-op</tt>.
 980 </blockquote>
 981
 982
 983
 984 <a name='sect-text'><h4>Text</h4></a>
 985
 986 <p>Vecto can draw text to a canvas. It loads glyph shapes from
 987   TrueType font files
 988   with <a href="http://www.xach.com/lisp/zpb-ttf/">ZPB-TTF</a>.
 989
 990 <p><a name='get-font'>[Function]</a><br>
 991 <b>get-font</b> <i>font-file</i> => <i>font-loader</i>
 992
 993 <blockquote>
 994 Creates and returns a ZPB-TTF font loader object
 995 from <i>font-file</i>. Any font loader created this way will
 996 automatically be closed at the end of its
 997 enclosing <a href='#with-canvas'><tt>WITH-CANVAS</tt></a> form.
 998 </blockquote>
 999
1000
1001 <p><a name='set-font'>[Function]</a><br>
1002 <b>set-font</b> <i>font-loader</i> <i>size</i> => |
1003
1004 <blockquote>
1005 Sets the active font to the font associated
1006 with <i>font-loader</i>, scaled to <i>size</i> units per line.
1007
1008 <p>The first argument can be any ZPB-TTF font loader; it need not be
1009 created via <a href='#get-font'><tt>GET-FONT</tt></a>. However, only
1010 font loaders created via <tt>GET-FONT</tt> will be automatically
1011 closed at the end of <a href='#with-canvas'><tt>WITH-CANVAS</tt></a>.
1012 </blockquote>
1013
1014
1015 <p><a name='set-character-spacing'>[Function]</a><br>
1016 <b>set-character-spacing</b> <i>spacing</i> => |
1017
1018 <blockquote>
1019 Sets the scale of the spacing used between characters when drawing
1020 text with <a href='#draw-string'><tt>DRAW-STRING</tt></a> and related
1021 functions.
1022
1023 <p>Normally, the character spacing for drawing text is taken directly
1024   from a font's advance-width and kerning
1025   metrics. <tt>SET-CHARACTER-SPACING</tt> can be used to adjust this
1026   spacing; for example, a character spacing of 2.0d0 would double the
1027   normal space between characters, and 0.5d0 would halve it.
1028 </blockquote>
1029
1030 <p><a name='*default-character-spacing*'>[Special variable]</a><br>
1031 <b>*default-character-spacing*</b>
1032
1033 <blockquote>
1034 The default scale for character spacing when drawing text
1035 with <a href='#draw-string'><tt>DRAW-STRING</tt></a> and related
1036 functions. Initial value is 1.0d0.
1037
1038 <p>Changes to this variable affect the
1039   next <a href='#with-canvas'><tt>WITH-CANVAS</tt></a> form. To affect
1040   the spacing within the current <tt>WITH-CANVAS</tt> form,
1041   use <a href='#set-character-spacing'><tt>SET-CHARACTER-SPACING</tt></a>.
1042 </blockquote>
1043
1044
1045 <p><a name='draw-string'>[Function]</a><br>
1046 <b>draw-string</b> <i>x</i> <i>y</i> <i>string</i> => |
1047
1048 <blockquote>
1049 Draws <i>string</i> on the canvas with the active font. The glyph
1050 origin of the first character in the string is positioned at <i>x</i>
1051 and the baseline of the string is positioned at <i>y</i>. The text is
1052 filled with the current <a href='#set-rgba-fill'>fill color</a>.
1053
1054 <p>The string may be a specialized vector of characters (a true CL
1055 string) or a vector containing characters, Unicode code-points, or both. For
1056 example, <tt>#(#\L #\a #\m #\b #\d #\a #\= #x3BB)</tt> is a valid
1057 argument for <tt>DRAW-STRING</tt>.
1058
1059 <p>The horizontal space between characters is determined by the
1060 advance-width and kerning metrics of the font, then multiplied by
1061 the current character spacing. At the default character spacing of
1062 1.0d0, the spacing is not adjusted at
1063 all. <a href='#set-character-spacing'><tt>SET-CHARACTER-SPACING</tt></a>
1064 can be used to increase or decrease the character spacing.
1065 </blockquote>
1066
1067
1068 <p><a name='string-paths'>[Function]</a><br>
1069 <b>string-paths</b> <i>x</i> <i>y</i> <i>string</i> => |
1070
1071 <blockquote>
1072 Like <a href='#draw-string'><tt>DRAW-STRING</tt></a>, but instead of
1073 drawing the text, adds the subpaths that make up the string glyphs to
1074 the graphics state. This can be used to stroke, fill, or clip based on
1075 the outlines of a string.
1076 </blockquote>
1077
1078
1079 <p><a name='draw-centered-string'>[Function]</a><br>
1080 <b>draw-centered-string</b> <i>x</i> <i>y</i> <i>string</i> => |
1081
1082 <blockquote>
1083 Draws <i>string</i> on the canvas with the active font. The horizontal
1084 center of the string is positioned at <i>x</i> and the baseline of the
1085 string is positioned at <i>y</i>.
1086 </blockquote>
1087
1088
1089 <p><a name='centered-string-paths'>[Function]</a><br>
1090 <b>centered-string-paths</b> <i>x</i> <i>y</i> <i>string</i> => |
1091
1092 <blockquote>
1093 Like <a href='#draw-centered-string'><tt>DRAW-CENTERED-STRING</tt></a>,
1094 but adds subpaths instead of painting. See
1095 also <a href='#string-paths'><tt>STRING-PATHS</tt></a>.
1096 </blockquote>
1097
1098
1099 <p><a name='string-bounding-box'>[Function]</a><br>
1100 <b>string-bounding-box</b> <i>string</i> <i>size</i> <i>loader</i>
1101 => <i>#(xmin ymin xmax ymax)</i>
1102
1103 <blockquote>
1104 Calculates the bounding box of <i>string</i> for <i>font-loader</i>
1105 at <i>size</i>.
1106 </blockquote>
1107
1108
1109 <a name='sect-miscellaneous'><h3>Miscellaneous</h3></a>
1110
1111 <p><a name='const-kappa'>[Constant]</a><br>
1112 <b>+kappa+</b> => 0.5522847498307936d0.
1113
1114 <blockquote>
1115 This constant is useful to draw portions of a circle.
1116 </blockquote>
1117
1118
1119 <a name='sect-references'><h2>References</h2></a>
1120
1121 <ul>
1122   <li> Adobe Systems Inc., <a href="http://www.adobe.com/devnet/pdf/pdf_reference.html">PDF Reference, Sixth Edition, Version 1.7</a>
1123   <li> Lawrence Kesteloot, <a href="http://www.teamten.com/lawrence/graphics/premultiplication/">Alpha Premultiplication</a>
1124   <li> Dr. Thomas Sederberg, <a href="http://www.tsplines.com/resources/class_notes/Bezier_curves.pdf">B&eacute;zier curves</a>
1125   <li> Alvy Ray Smith, <a href="http://alvyray.com/Memos/MemosMicrosoft.htm#ImageCompositing">Image Compositing Fundamentals</a>
1126   <li> G. Adam Stanislav, <a href="http://www.whizkidtech.redprince.net/bezier/circle/">Drawing a circle with B&eacute;zier curves</a>
1127   <li> Alexander Thomas, <a href="http://www.dr-lex.be/random/matrix_inv.html">The Inverse and Determinants of 2x2 and 3x3 Matrices</a>
1128   <li> Wikipedia, <a href="http://en.wikipedia.org/wiki/B%C3%A9zier_curve">B&eacute;zier curve</a>
1129
1130 </ul>
1131
1132
1133 <a name='sect-acknowledgements'><h2>Acknowledgements</h2></a>
1134
1135 <p>Many thanks to <a href="http://www.elbeno.com/">Ben Deane</a> for
1136   permission to adapt code from his curve library for drawing arcs.
1137
1138 <p>Ryan Davis helped fix my adaptation of the arc drawing.
1139
1140 <a name='sect-feedback'><h2>Feedback</h2></a>
1141
1142 <p>If you have any questions, comments, bug reports, or other feedback
1143 regarding Vecto, please email <a href="mailto:xach@xach.com">Zach
1144 Beane</a>.
1145
1146
1147 </div>
1148 </body>