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modules/freetype2/include/ftstroke.h

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1 /***************************************************************************/
2 /* */
3 /* ftstroke.h */
4 /* */
5 /* FreeType path stroker (specification). */
6 /* */
7 /* Copyright 2002-2006, 2008, 2009, 2011-2012 by */
8 /* David Turner, Robert Wilhelm, and Werner Lemberg. */
9 /* */
10 /* This file is part of the FreeType project, and may only be used, */
11 /* modified, and distributed under the terms of the FreeType project */
12 /* license, LICENSE.TXT. By continuing to use, modify, or distribute */
13 /* this file you indicate that you have read the license and */
14 /* understand and accept it fully. */
15 /* */
16 /***************************************************************************/
17
18
19 #ifndef __FT_STROKE_H__
20 #define __FT_STROKE_H__
21
22 #include <ft2build.h>
23 #include FT_OUTLINE_H
24 #include FT_GLYPH_H
25
26
27 FT_BEGIN_HEADER
28
29
30 /************************************************************************
31 *
32 * @section:
33 * glyph_stroker
34 *
35 * @title:
36 * Glyph Stroker
37 *
38 * @abstract:
39 * Generating bordered and stroked glyphs.
40 *
41 * @description:
42 * This component generates stroked outlines of a given vectorial
43 * glyph. It also allows you to retrieve the `outside' and/or the
44 * `inside' borders of the stroke.
45 *
46 * This can be useful to generate `bordered' glyph, i.e., glyphs
47 * displayed with a coloured (and anti-aliased) border around their
48 * shape.
49 */
50
51
52 /**************************************************************
53 *
54 * @type:
55 * FT_Stroker
56 *
57 * @description:
58 * Opaque handler to a path stroker object.
59 */
60 typedef struct FT_StrokerRec_* FT_Stroker;
61
62
63 /**************************************************************
64 *
65 * @enum:
66 * FT_Stroker_LineJoin
67 *
68 * @description:
69 * These values determine how two joining lines are rendered
70 * in a stroker.
71 *
72 * @values:
73 * FT_STROKER_LINEJOIN_ROUND ::
74 * Used to render rounded line joins. Circular arcs are used
75 * to join two lines smoothly.
76 *
77 * FT_STROKER_LINEJOIN_BEVEL ::
78 * Used to render beveled line joins. The outer corner of
79 * the joined lines is filled by enclosing the triangular
80 * region of the corner with a straight line between the
81 * outer corners of each stroke.
82 *
83 * FT_STROKER_LINEJOIN_MITER_FIXED ::
84 * Used to render mitered line joins, with fixed bevels if the
85 * miter limit is exceeded. The outer edges of the strokes
86 * for the two segments are extended until they meet at an
87 * angle. If the segments meet at too sharp an angle (such
88 * that the miter would extend from the intersection of the
89 * segments a distance greater than the product of the miter
90 * limit value and the border radius), then a bevel join (see
91 * above) is used instead. This prevents long spikes being
92 * created. FT_STROKER_LINEJOIN_MITER_FIXED generates a miter
93 * line join as used in PostScript and PDF.
94 *
95 * FT_STROKER_LINEJOIN_MITER_VARIABLE ::
96 * FT_STROKER_LINEJOIN_MITER ::
97 * Used to render mitered line joins, with variable bevels if
98 * the miter limit is exceeded. The intersection of the
99 * strokes is clipped at a line perpendicular to the bisector
100 * of the angle between the strokes, at the distance from the
101 * intersection of the segments equal to the product of the
102 * miter limit value and the border radius. This prevents
103 * long spikes being created.
104 * FT_STROKER_LINEJOIN_MITER_VARIABLE generates a mitered line
105 * join as used in XPS. FT_STROKER_LINEJOIN_MITER is an alias
106 * for FT_STROKER_LINEJOIN_MITER_VARIABLE, retained for
107 * backwards compatibility.
108 */
109 typedef enum FT_Stroker_LineJoin_
110 {
111 FT_STROKER_LINEJOIN_ROUND = 0,
112 FT_STROKER_LINEJOIN_BEVEL = 1,
113 FT_STROKER_LINEJOIN_MITER_VARIABLE = 2,
114 FT_STROKER_LINEJOIN_MITER = FT_STROKER_LINEJOIN_MITER_VARIABLE,
115 FT_STROKER_LINEJOIN_MITER_FIXED = 3
116
117 } FT_Stroker_LineJoin;
118
119
120 /**************************************************************
121 *
122 * @enum:
123 * FT_Stroker_LineCap
124 *
125 * @description:
126 * These values determine how the end of opened sub-paths are
127 * rendered in a stroke.
128 *
129 * @values:
130 * FT_STROKER_LINECAP_BUTT ::
131 * The end of lines is rendered as a full stop on the last
132 * point itself.
133 *
134 * FT_STROKER_LINECAP_ROUND ::
135 * The end of lines is rendered as a half-circle around the
136 * last point.
137 *
138 * FT_STROKER_LINECAP_SQUARE ::
139 * The end of lines is rendered as a square around the
140 * last point.
141 */
142 typedef enum FT_Stroker_LineCap_
143 {
144 FT_STROKER_LINECAP_BUTT = 0,
145 FT_STROKER_LINECAP_ROUND,
146 FT_STROKER_LINECAP_SQUARE
147
148 } FT_Stroker_LineCap;
149
150
151 /**************************************************************
152 *
153 * @enum:
154 * FT_StrokerBorder
155 *
156 * @description:
157 * These values are used to select a given stroke border
158 * in @FT_Stroker_GetBorderCounts and @FT_Stroker_ExportBorder.
159 *
160 * @values:
161 * FT_STROKER_BORDER_LEFT ::
162 * Select the left border, relative to the drawing direction.
163 *
164 * FT_STROKER_BORDER_RIGHT ::
165 * Select the right border, relative to the drawing direction.
166 *
167 * @note:
168 * Applications are generally interested in the `inside' and `outside'
169 * borders. However, there is no direct mapping between these and the
170 * `left' and `right' ones, since this really depends on the glyph's
171 * drawing orientation, which varies between font formats.
172 *
173 * You can however use @FT_Outline_GetInsideBorder and
174 * @FT_Outline_GetOutsideBorder to get these.
175 */
176 typedef enum FT_StrokerBorder_
177 {
178 FT_STROKER_BORDER_LEFT = 0,
179 FT_STROKER_BORDER_RIGHT
180
181 } FT_StrokerBorder;
182
183
184 /**************************************************************
185 *
186 * @function:
187 * FT_Outline_GetInsideBorder
188 *
189 * @description:
190 * Retrieve the @FT_StrokerBorder value corresponding to the
191 * `inside' borders of a given outline.
192 *
193 * @input:
194 * outline ::
195 * The source outline handle.
196 *
197 * @return:
198 * The border index. @FT_STROKER_BORDER_RIGHT for empty or invalid
199 * outlines.
200 */
201 FT_EXPORT( FT_StrokerBorder )
202 FT_Outline_GetInsideBorder( FT_Outline* outline );
203
204
205 /**************************************************************
206 *
207 * @function:
208 * FT_Outline_GetOutsideBorder
209 *
210 * @description:
211 * Retrieve the @FT_StrokerBorder value corresponding to the
212 * `outside' borders of a given outline.
213 *
214 * @input:
215 * outline ::
216 * The source outline handle.
217 *
218 * @return:
219 * The border index. @FT_STROKER_BORDER_LEFT for empty or invalid
220 * outlines.
221 */
222 FT_EXPORT( FT_StrokerBorder )
223 FT_Outline_GetOutsideBorder( FT_Outline* outline );
224
225
226 /**************************************************************
227 *
228 * @function:
229 * FT_Stroker_New
230 *
231 * @description:
232 * Create a new stroker object.
233 *
234 * @input:
235 * library ::
236 * FreeType library handle.
237 *
238 * @output:
239 * astroker ::
240 * A new stroker object handle. NULL in case of error.
241 *
242 * @return:
243 * FreeType error code. 0~means success.
244 */
245 FT_EXPORT( FT_Error )
246 FT_Stroker_New( FT_Library library,
247 FT_Stroker *astroker );
248
249
250 /**************************************************************
251 *
252 * @function:
253 * FT_Stroker_Set
254 *
255 * @description:
256 * Reset a stroker object's attributes.
257 *
258 * @input:
259 * stroker ::
260 * The target stroker handle.
261 *
262 * radius ::
263 * The border radius.
264 *
265 * line_cap ::
266 * The line cap style.
267 *
268 * line_join ::
269 * The line join style.
270 *
271 * miter_limit ::
272 * The miter limit for the FT_STROKER_LINEJOIN_MITER_FIXED and
273 * FT_STROKER_LINEJOIN_MITER_VARIABLE line join styles,
274 * expressed as 16.16 fixed-point value.
275 *
276 * @note:
277 * The radius is expressed in the same units as the outline
278 * coordinates.
279 */
280 FT_EXPORT( void )
281 FT_Stroker_Set( FT_Stroker stroker,
282 FT_Fixed radius,
283 FT_Stroker_LineCap line_cap,
284 FT_Stroker_LineJoin line_join,
285 FT_Fixed miter_limit );
286
287
288 /**************************************************************
289 *
290 * @function:
291 * FT_Stroker_Rewind
292 *
293 * @description:
294 * Reset a stroker object without changing its attributes.
295 * You should call this function before beginning a new
296 * series of calls to @FT_Stroker_BeginSubPath or
297 * @FT_Stroker_EndSubPath.
298 *
299 * @input:
300 * stroker ::
301 * The target stroker handle.
302 */
303 FT_EXPORT( void )
304 FT_Stroker_Rewind( FT_Stroker stroker );
305
306
307 /**************************************************************
308 *
309 * @function:
310 * FT_Stroker_ParseOutline
311 *
312 * @description:
313 * A convenience function used to parse a whole outline with
314 * the stroker. The resulting outline(s) can be retrieved
315 * later by functions like @FT_Stroker_GetCounts and @FT_Stroker_Export.
316 *
317 * @input:
318 * stroker ::
319 * The target stroker handle.
320 *
321 * outline ::
322 * The source outline.
323 *
324 * opened ::
325 * A boolean. If~1, the outline is treated as an open path instead
326 * of a closed one.
327 *
328 * @return:
329 * FreeType error code. 0~means success.
330 *
331 * @note:
332 * If `opened' is~0 (the default), the outline is treated as a closed
333 * path, and the stroker generates two distinct `border' outlines.
334 *
335 * If `opened' is~1, the outline is processed as an open path, and the
336 * stroker generates a single `stroke' outline.
337 *
338 * This function calls @FT_Stroker_Rewind automatically.
339 */
340 FT_EXPORT( FT_Error )
341 FT_Stroker_ParseOutline( FT_Stroker stroker,
342 FT_Outline* outline,
343 FT_Bool opened );
344
345
346 /**************************************************************
347 *
348 * @function:
349 * FT_Stroker_BeginSubPath
350 *
351 * @description:
352 * Start a new sub-path in the stroker.
353 *
354 * @input:
355 * stroker ::
356 * The target stroker handle.
357 *
358 * to ::
359 * A pointer to the start vector.
360 *
361 * open ::
362 * A boolean. If~1, the sub-path is treated as an open one.
363 *
364 * @return:
365 * FreeType error code. 0~means success.
366 *
367 * @note:
368 * This function is useful when you need to stroke a path that is
369 * not stored as an @FT_Outline object.
370 */
371 FT_EXPORT( FT_Error )
372 FT_Stroker_BeginSubPath( FT_Stroker stroker,
373 FT_Vector* to,
374 FT_Bool open );
375
376
377 /**************************************************************
378 *
379 * @function:
380 * FT_Stroker_EndSubPath
381 *
382 * @description:
383 * Close the current sub-path in the stroker.
384 *
385 * @input:
386 * stroker ::
387 * The target stroker handle.
388 *
389 * @return:
390 * FreeType error code. 0~means success.
391 *
392 * @note:
393 * You should call this function after @FT_Stroker_BeginSubPath.
394 * If the subpath was not `opened', this function `draws' a
395 * single line segment to the start position when needed.
396 */
397 FT_EXPORT( FT_Error )
398 FT_Stroker_EndSubPath( FT_Stroker stroker );
399
400
401 /**************************************************************
402 *
403 * @function:
404 * FT_Stroker_LineTo
405 *
406 * @description:
407 * `Draw' a single line segment in the stroker's current sub-path,
408 * from the last position.
409 *
410 * @input:
411 * stroker ::
412 * The target stroker handle.
413 *
414 * to ::
415 * A pointer to the destination point.
416 *
417 * @return:
418 * FreeType error code. 0~means success.
419 *
420 * @note:
421 * You should call this function between @FT_Stroker_BeginSubPath and
422 * @FT_Stroker_EndSubPath.
423 */
424 FT_EXPORT( FT_Error )
425 FT_Stroker_LineTo( FT_Stroker stroker,
426 FT_Vector* to );
427
428
429 /**************************************************************
430 *
431 * @function:
432 * FT_Stroker_ConicTo
433 *
434 * @description:
435 * `Draw' a single quadratic Bézier in the stroker's current sub-path,
436 * from the last position.
437 *
438 * @input:
439 * stroker ::
440 * The target stroker handle.
441 *
442 * control ::
443 * A pointer to a Bézier control point.
444 *
445 * to ::
446 * A pointer to the destination point.
447 *
448 * @return:
449 * FreeType error code. 0~means success.
450 *
451 * @note:
452 * You should call this function between @FT_Stroker_BeginSubPath and
453 * @FT_Stroker_EndSubPath.
454 */
455 FT_EXPORT( FT_Error )
456 FT_Stroker_ConicTo( FT_Stroker stroker,
457 FT_Vector* control,
458 FT_Vector* to );
459
460
461 /**************************************************************
462 *
463 * @function:
464 * FT_Stroker_CubicTo
465 *
466 * @description:
467 * `Draw' a single cubic Bézier in the stroker's current sub-path,
468 * from the last position.
469 *
470 * @input:
471 * stroker ::
472 * The target stroker handle.
473 *
474 * control1 ::
475 * A pointer to the first Bézier control point.
476 *
477 * control2 ::
478 * A pointer to second Bézier control point.
479 *
480 * to ::
481 * A pointer to the destination point.
482 *
483 * @return:
484 * FreeType error code. 0~means success.
485 *
486 * @note:
487 * You should call this function between @FT_Stroker_BeginSubPath and
488 * @FT_Stroker_EndSubPath.
489 */
490 FT_EXPORT( FT_Error )
491 FT_Stroker_CubicTo( FT_Stroker stroker,
492 FT_Vector* control1,
493 FT_Vector* control2,
494 FT_Vector* to );
495
496
497 /**************************************************************
498 *
499 * @function:
500 * FT_Stroker_GetBorderCounts
501 *
502 * @description:
503 * Call this function once you have finished parsing your paths
504 * with the stroker. It returns the number of points and
505 * contours necessary to export one of the `border' or `stroke'
506 * outlines generated by the stroker.
507 *
508 * @input:
509 * stroker ::
510 * The target stroker handle.
511 *
512 * border ::
513 * The border index.
514 *
515 * @output:
516 * anum_points ::
517 * The number of points.
518 *
519 * anum_contours ::
520 * The number of contours.
521 *
522 * @return:
523 * FreeType error code. 0~means success.
524 *
525 * @note:
526 * When an outline, or a sub-path, is `closed', the stroker generates
527 * two independent `border' outlines, named `left' and `right'.
528 *
529 * When the outline, or a sub-path, is `opened', the stroker merges
530 * the `border' outlines with caps. The `left' border receives all
531 * points, while the `right' border becomes empty.
532 *
533 * Use the function @FT_Stroker_GetCounts instead if you want to
534 * retrieve the counts associated to both borders.
535 */
536 FT_EXPORT( FT_Error )
537 FT_Stroker_GetBorderCounts( FT_Stroker stroker,
538 FT_StrokerBorder border,
539 FT_UInt *anum_points,
540 FT_UInt *anum_contours );
541
542
543 /**************************************************************
544 *
545 * @function:
546 * FT_Stroker_ExportBorder
547 *
548 * @description:
549 * Call this function after @FT_Stroker_GetBorderCounts to
550 * export the corresponding border to your own @FT_Outline
551 * structure.
552 *
553 * Note that this function appends the border points and
554 * contours to your outline, but does not try to resize its
555 * arrays.
556 *
557 * @input:
558 * stroker ::
559 * The target stroker handle.
560 *
561 * border ::
562 * The border index.
563 *
564 * outline ::
565 * The target outline handle.
566 *
567 * @note:
568 * Always call this function after @FT_Stroker_GetBorderCounts to
569 * get sure that there is enough room in your @FT_Outline object to
570 * receive all new data.
571 *
572 * When an outline, or a sub-path, is `closed', the stroker generates
573 * two independent `border' outlines, named `left' and `right'
574 *
575 * When the outline, or a sub-path, is `opened', the stroker merges
576 * the `border' outlines with caps. The `left' border receives all
577 * points, while the `right' border becomes empty.
578 *
579 * Use the function @FT_Stroker_Export instead if you want to
580 * retrieve all borders at once.
581 */
582 FT_EXPORT( void )
583 FT_Stroker_ExportBorder( FT_Stroker stroker,
584 FT_StrokerBorder border,
585 FT_Outline* outline );
586
587
588 /**************************************************************
589 *
590 * @function:
591 * FT_Stroker_GetCounts
592 *
593 * @description:
594 * Call this function once you have finished parsing your paths
595 * with the stroker. It returns the number of points and
596 * contours necessary to export all points/borders from the stroked
597 * outline/path.
598 *
599 * @input:
600 * stroker ::
601 * The target stroker handle.
602 *
603 * @output:
604 * anum_points ::
605 * The number of points.
606 *
607 * anum_contours ::
608 * The number of contours.
609 *
610 * @return:
611 * FreeType error code. 0~means success.
612 */
613 FT_EXPORT( FT_Error )
614 FT_Stroker_GetCounts( FT_Stroker stroker,
615 FT_UInt *anum_points,
616 FT_UInt *anum_contours );
617
618
619 /**************************************************************
620 *
621 * @function:
622 * FT_Stroker_Export
623 *
624 * @description:
625 * Call this function after @FT_Stroker_GetBorderCounts to
626 * export all borders to your own @FT_Outline structure.
627 *
628 * Note that this function appends the border points and
629 * contours to your outline, but does not try to resize its
630 * arrays.
631 *
632 * @input:
633 * stroker ::
634 * The target stroker handle.
635 *
636 * outline ::
637 * The target outline handle.
638 */
639 FT_EXPORT( void )
640 FT_Stroker_Export( FT_Stroker stroker,
641 FT_Outline* outline );
642
643
644 /**************************************************************
645 *
646 * @function:
647 * FT_Stroker_Done
648 *
649 * @description:
650 * Destroy a stroker object.
651 *
652 * @input:
653 * stroker ::
654 * A stroker handle. Can be NULL.
655 */
656 FT_EXPORT( void )
657 FT_Stroker_Done( FT_Stroker stroker );
658
659
660 /**************************************************************
661 *
662 * @function:
663 * FT_Glyph_Stroke
664 *
665 * @description:
666 * Stroke a given outline glyph object with a given stroker.
667 *
668 * @inout:
669 * pglyph ::
670 * Source glyph handle on input, new glyph handle on output.
671 *
672 * @input:
673 * stroker ::
674 * A stroker handle.
675 *
676 * destroy ::
677 * A Boolean. If~1, the source glyph object is destroyed
678 * on success.
679 *
680 * @return:
681 * FreeType error code. 0~means success.
682 *
683 * @note:
684 * The source glyph is untouched in case of error.
685 *
686 * Adding stroke may yield a significantly wider and taller glyph
687 * depending on how large of a radius was used to stroke the glyph. You
688 * may need to manually adjust horizontal and vertical advance amounts
689 * to account for this added size.
690 */
691 FT_EXPORT( FT_Error )
692 FT_Glyph_Stroke( FT_Glyph *pglyph,
693 FT_Stroker stroker,
694 FT_Bool destroy );
695
696
697 /**************************************************************
698 *
699 * @function:
700 * FT_Glyph_StrokeBorder
701 *
702 * @description:
703 * Stroke a given outline glyph object with a given stroker, but
704 * only return either its inside or outside border.
705 *
706 * @inout:
707 * pglyph ::
708 * Source glyph handle on input, new glyph handle on output.
709 *
710 * @input:
711 * stroker ::
712 * A stroker handle.
713 *
714 * inside ::
715 * A Boolean. If~1, return the inside border, otherwise
716 * the outside border.
717 *
718 * destroy ::
719 * A Boolean. If~1, the source glyph object is destroyed
720 * on success.
721 *
722 * @return:
723 * FreeType error code. 0~means success.
724 *
725 * @note:
726 * The source glyph is untouched in case of error.
727 *
728 * Adding stroke may yield a significantly wider and taller glyph
729 * depending on how large of a radius was used to stroke the glyph. You
730 * may need to manually adjust horizontal and vertical advance amounts
731 * to account for this added size.
732 */
733 FT_EXPORT( FT_Error )
734 FT_Glyph_StrokeBorder( FT_Glyph *pglyph,
735 FT_Stroker stroker,
736 FT_Bool inside,
737 FT_Bool destroy );
738
739 /* */
740
741 FT_END_HEADER
742
743 #endif /* __FT_STROKE_H__ */
744
745
746 /* END */
747
748
749 /* Local Variables: */
750 /* coding: utf-8 */
751 /* End: */

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