docs/reference/ft2-layer_management.html

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 114               FreeType-2.10.4 API Reference
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 118                 Glyph Layer Management
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 215       General Remarks
 216     </label>
 217     <nav class="md-nav" data-md-component="collapsible" data-md-level="1">
 218       <label class="md-nav__title" for="nav-3">
 219         General Remarks
 220       </label>
 221       <ul class="md-nav__list" data-md-scrollfix>
 222
 223
 224
 225
 226
 227
 228
 229   <li class="md-nav__item">
 230     <a href="ft2-header_inclusion.html" title="FreeType's header inclusion scheme" class="md-nav__link">
 231       FreeType's header inclusion scheme
 232     </a>
 233   </li>
 234
 235
 236
 237
 238
 239
 240
 241   <li class="md-nav__item">
 242     <a href="ft2-user_allocation.html" title="User allocation" class="md-nav__link">
 243       User allocation
 244     </a>
 245   </li>
 246
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 264     <label class="md-nav__link" for="nav-4">
 265       Core API
 266     </label>
 267     <nav class="md-nav" data-md-component="collapsible" data-md-level="1">
 268       <label class="md-nav__title" for="nav-4">
 269         Core API
 270       </label>
 271       <ul class="md-nav__list" data-md-scrollfix>
 272
 273
 274
 275
 276
 277
 278
 279   <li class="md-nav__item">
 280     <a href="ft2-version.html" title="FreeType Version" class="md-nav__link">
 281       FreeType Version
 282     </a>
 283   </li>
 284
 285
 286
 287
 288
 289
 290
 291   <li class="md-nav__item">
 292     <a href="ft2-basic_types.html" title="Basic Data Types" class="md-nav__link">
 293       Basic Data Types
 294     </a>
 295   </li>
 296
 297
 298
 299
 300
 301
 302
 303   <li class="md-nav__item">
 304     <a href="ft2-base_interface.html" title="Base Interface" class="md-nav__link">
 305       Base Interface
 306     </a>
 307   </li>
 308
 309
 310
 311
 312
 313
 314
 315   <li class="md-nav__item">
 316     <a href="ft2-glyph_variants.html" title="Unicode Variation Sequences" class="md-nav__link">
 317       Unicode Variation Sequences
 318     </a>
 319   </li>
 320
 321
 322
 323
 324
 325
 326
 327   <li class="md-nav__item">
 328     <a href="ft2-color_management.html" title="Glyph Color Management" class="md-nav__link">
 329       Glyph Color Management
 330     </a>
 331   </li>
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341   <li class="md-nav__item md-nav__item--active">
 342
 343     <input class="md-toggle md-nav__toggle" data-md-toggle="toc" type="checkbox" id="__toc">
 344
 345
 346
 347
 348       <label class="md-nav__link md-nav__link--active" for="__toc">
 349         Glyph Layer Management
 350       </label>
 351
 352     <a href="ft2-layer_management.html" title="Glyph Layer Management" class="md-nav__link md-nav__link--active">
 353       Glyph Layer Management
 354     </a>
 355
 356
 357 <nav class="md-nav md-nav--secondary">
 358
 359
 360
 361
 362
 363     <label class="md-nav__title" for="__toc">Table of contents</label>
 364     <ul class="md-nav__list" data-md-scrollfix>
 365
 366         <li class="md-nav__item">
 367   <a href="#synopsis" class="md-nav__link">
 368     Synopsis
 369   </a>
 370
 371 </li>
 372
 373         <li class="md-nav__item">
 374   <a href="#ft_layeriterator" class="md-nav__link">
 375     FT_LayerIterator
 376   </a>
 377
 378 </li>
 379
 380         <li class="md-nav__item">
 381   <a href="#ft_get_color_glyph_layer" class="md-nav__link">
 382     FT_Get_Color_Glyph_Layer
 383   </a>
 384
 385 </li>
 386
 387
 388
 389
 390
 391     </ul>
 392
 393 </nav>
 394
 395   </li>
 396
 397
 398
 399
 400
 401
 402
 403   <li class="md-nav__item">
 404     <a href="ft2-glyph_management.html" title="Glyph Management" class="md-nav__link">
 405       Glyph Management
 406     </a>
 407   </li>
 408
 409
 410
 411
 412
 413
 414
 415   <li class="md-nav__item">
 416     <a href="ft2-mac_specific.html" title="Mac Specific Interface" class="md-nav__link">
 417       Mac Specific Interface
 418     </a>
 419   </li>
 420
 421
 422
 423
 424
 425
 426
 427   <li class="md-nav__item">
 428     <a href="ft2-sizes_management.html" title="Size Management" class="md-nav__link">
 429       Size Management
 430     </a>
 431   </li>
 432
 433
 434
 435
 436
 437
 438
 439   <li class="md-nav__item">
 440     <a href="ft2-header_file_macros.html" title="Header File Macros" class="md-nav__link">
 441       Header File Macros
 442     </a>
 443   </li>
 444
 445
 446       </ul>
 447     </nav>
 448   </li>
 449
 450
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 456   <li class="md-nav__item md-nav__item--nested">
 457
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 459
 460     <label class="md-nav__link" for="nav-5">
 461       Format-Specific API
 462     </label>
 463     <nav class="md-nav" data-md-component="collapsible" data-md-level="1">
 464       <label class="md-nav__title" for="nav-5">
 465         Format-Specific API
 466       </label>
 467       <ul class="md-nav__list" data-md-scrollfix>
 468
 469
 470
 471
 472
 473
 474
 475   <li class="md-nav__item">
 476     <a href="ft2-multiple_masters.html" title="Multiple Masters" class="md-nav__link">
 477       Multiple Masters
 478     </a>
 479   </li>
 480
 481
 482
 483
 484
 485
 486
 487   <li class="md-nav__item">
 488     <a href="ft2-truetype_tables.html" title="TrueType Tables" class="md-nav__link">
 489       TrueType Tables
 490     </a>
 491   </li>
 492
 493
 494
 495
 496
 497
 498
 499   <li class="md-nav__item">
 500     <a href="ft2-type1_tables.html" title="Type 1 Tables" class="md-nav__link">
 501       Type 1 Tables
 502     </a>
 503   </li>
 504
 505
 506
 507
 508
 509
 510
 511   <li class="md-nav__item">
 512     <a href="ft2-sfnt_names.html" title="SFNT Names" class="md-nav__link">
 513       SFNT Names
 514     </a>
 515   </li>
 516
 517
 518
 519
 520
 521
 522
 523   <li class="md-nav__item">
 524     <a href="ft2-bdf_fonts.html" title="BDF and PCF Files" class="md-nav__link">
 525       BDF and PCF Files
 526     </a>
 527   </li>
 528
 529
 530
 531
 532
 533
 534
 535   <li class="md-nav__item">
 536     <a href="ft2-cid_fonts.html" title="CID Fonts" class="md-nav__link">
 537       CID Fonts
 538     </a>
 539   </li>
 540
 541
 542
 543
 544
 545
 546
 547   <li class="md-nav__item">
 548     <a href="ft2-pfr_fonts.html" title="PFR Fonts" class="md-nav__link">
 549       PFR Fonts
 550     </a>
 551   </li>
 552
 553
 554
 555
 556
 557
 558
 559   <li class="md-nav__item">
 560     <a href="ft2-winfnt_fonts.html" title="Window FNT Files" class="md-nav__link">
 561       Window FNT Files
 562     </a>
 563   </li>
 564
 565
 566
 567
 568
 569
 570
 571   <li class="md-nav__item">
 572     <a href="ft2-font_formats.html" title="Font Formats" class="md-nav__link">
 573       Font Formats
 574     </a>
 575   </li>
 576
 577
 578
 579
 580
 581
 582
 583   <li class="md-nav__item">
 584     <a href="ft2-gasp_table.html" title="Gasp Table" class="md-nav__link">
 585       Gasp Table
 586     </a>
 587   </li>
 588
 589
 590       </ul>
 591     </nav>
 592   </li>
 593
 594
 595
 596
 597
 598
 599
 600   <li class="md-nav__item md-nav__item--nested">
 601
 602       <input class="md-toggle md-nav__toggle" data-md-toggle="nav-6" type="checkbox" id="nav-6">
 603
 604     <label class="md-nav__link" for="nav-6">
 605       Controlling FreeType Modules
 606     </label>
 607     <nav class="md-nav" data-md-component="collapsible" data-md-level="1">
 608       <label class="md-nav__title" for="nav-6">
 609         Controlling FreeType Modules
 610       </label>
 611       <ul class="md-nav__list" data-md-scrollfix>
 612
 613
 614
 615
 616
 617
 618
 619   <li class="md-nav__item">
 620     <a href="ft2-auto_hinter.html" title="The auto-hinter" class="md-nav__link">
 621       The auto-hinter
 622     </a>
 623   </li>
 624
 625
 626
 627
 628
 629
 630
 631   <li class="md-nav__item">
 632     <a href="ft2-cff_driver.html" title="The CFF driver" class="md-nav__link">
 633       The CFF driver
 634     </a>
 635   </li>
 636
 637
 638
 639
 640
 641
 642
 643   <li class="md-nav__item">
 644     <a href="ft2-t1_cid_driver.html" title="The Type 1 and CID drivers" class="md-nav__link">
 645       The Type 1 and CID drivers
 646     </a>
 647   </li>
 648
 649
 650
 651
 652
 653
 654
 655   <li class="md-nav__item">
 656     <a href="ft2-tt_driver.html" title="The TrueType driver" class="md-nav__link">
 657       The TrueType driver
 658     </a>
 659   </li>
 660
 661
 662
 663
 664
 665
 666
 667   <li class="md-nav__item">
 668     <a href="ft2-pcf_driver.html" title="The PCF driver" class="md-nav__link">
 669       The PCF driver
 670     </a>
 671   </li>
 672
 673
 674
 675
 676
 677
 678
 679   <li class="md-nav__item">
 680     <a href="ft2-properties.html" title="Driver properties" class="md-nav__link">
 681       Driver properties
 682     </a>
 683   </li>
 684
 685
 686
 687
 688
 689
 690
 691   <li class="md-nav__item">
 692     <a href="ft2-parameter_tags.html" title="Parameter Tags" class="md-nav__link">
 693       Parameter Tags
 694     </a>
 695   </li>
 696
 697
 698
 699
 700
 701
 702
 703   <li class="md-nav__item">
 704     <a href="ft2-lcd_rendering.html" title="Subpixel Rendering" class="md-nav__link">
 705       Subpixel Rendering
 706     </a>
 707   </li>
 708
 709
 710       </ul>
 711     </nav>
 712   </li>
 713
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 718
 719
 720   <li class="md-nav__item md-nav__item--nested">
 721
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 723
 724     <label class="md-nav__link" for="nav-7">
 725       Cache Sub-System
 726     </label>
 727     <nav class="md-nav" data-md-component="collapsible" data-md-level="1">
 728       <label class="md-nav__title" for="nav-7">
 729         Cache Sub-System
 730       </label>
 731       <ul class="md-nav__list" data-md-scrollfix>
 732
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 734
 735
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 737
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 739   <li class="md-nav__item">
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 788     <a href="ft2-list_processing.html" title="List Processing" class="md-nav__link">
 789       List Processing
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 798
 799   <li class="md-nav__item">
 800     <a href="ft2-outline_processing.html" title="Outline Processing" class="md-nav__link">
 801       Outline Processing
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 803   </li>
 804
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 811   <li class="md-nav__item">
 812     <a href="ft2-quick_advance.html" title="Quick retrieval of advance values" class="md-nav__link">
 813       Quick retrieval of advance values
 814     </a>
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 823   <li class="md-nav__item">
 824     <a href="ft2-bitmap_handling.html" title="Bitmap Handling" class="md-nav__link">
 825       Bitmap Handling
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 835   <li class="md-nav__item">
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 847   <li class="md-nav__item">
 848     <a href="ft2-glyph_stroker.html" title="Glyph Stroker" class="md-nav__link">
 849       Glyph Stroker
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 885       GZIP Streams
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 895   <li class="md-nav__item">
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1003   <li class="md-nav__item">
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1037
1038
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1050 <nav class="md-nav md-nav--secondary">
1051
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1055
1056     <label class="md-nav__title" for="__toc">Table of contents</label>
1057     <ul class="md-nav__list" data-md-scrollfix>
1058
1059         <li class="md-nav__item">
1060   <a href="#synopsis" class="md-nav__link">
1061     Synopsis
1062   </a>
1063
1064 </li>
1065
1066         <li class="md-nav__item">
1067   <a href="#ft_layeriterator" class="md-nav__link">
1068     FT_LayerIterator
1069   </a>
1070
1071 </li>
1072
1073         <li class="md-nav__item">
1074   <a href="#ft_get_color_glyph_layer" class="md-nav__link">
1075     FT_Get_Color_Glyph_Layer
1076   </a>
1077
1078 </li>
1079
1080
1081
1082
1083
1084     </ul>
1085
1086 </nav>
1087                   </div>
1088                 </div>
1089               </div>
1090
1091
1092           <div class="md-content">
1093             <article class="md-content__inner md-typeset">
1094
1095
1096
1097                 <p><a href="https://www.freetype.org">FreeType</a> &raquo; <a href="../">Docs</a> &raquo; <a href="index.html#core-api">Core API</a> &raquo; Glyph Layer Management</p>
1098 <hr />
1099 <h1 id="glyph-layer-management">Glyph Layer Management<a class="headerlink" href="#glyph-layer-management" title="Permanent link">&para;</a></h1>
1100 <h2 id="synopsis">Synopsis<a class="headerlink" href="#synopsis" title="Permanent link">&para;</a></h2>
1101 <p>The functions described here allow access of colored glyph layer data in OpenType's &lsquo;COLR&rsquo; tables.</p>
1102 <h2 id="ft_layeriterator">FT_LayerIterator<a class="headerlink" href="#ft_layeriterator" title="Permanent link">&para;</a></h2>
1103 <p>Defined in FT_FREETYPE_H (freetype/freetype.h).</p>
1104 <div class = "codehilite"><pre><code>  <span class="keyword">typedef</span> <span class="keyword">struct</span>  FT_LayerIterator_
1105   {
1106     <a href="ft2-basic_types.html#ft_uint">FT_UInt</a>   num_layers;
1107     <a href="ft2-basic_types.html#ft_uint">FT_UInt</a>   layer;
1108     <a href="ft2-basic_types.html#ft_byte">FT_Byte</a>*  p;
1109
1110   } <b>FT_LayerIterator</b>;
1111 </code></pre></div>
1112
1113 <p>This iterator object is needed for <code><a href="ft2-layer_management.html#ft_get_color_glyph_layer">FT_Get_Color_Glyph_Layer</a></code>.</p>
1114 <h4>fields</h4>
1115
1116 <table class="fields">
1117 <tr><td class="val" id="num_layers">num_layers</td><td class="desc">
1118 <p>The number of glyph layers for the requested glyph index. Will be set by <code><a href="ft2-layer_management.html#ft_get_color_glyph_layer">FT_Get_Color_Glyph_Layer</a></code>.</p>
1119 </td></tr>
1120 <tr><td class="val" id="layer">layer</td><td class="desc">
1121 <p>The current layer. Will be set by <code><a href="ft2-layer_management.html#ft_get_color_glyph_layer">FT_Get_Color_Glyph_Layer</a></code>.</p>
1122 </td></tr>
1123 <tr><td class="val" id="p">p</td><td class="desc">
1124 <p>An opaque pointer into &lsquo;COLR&rsquo; table data. The caller must set this to <code>NULL</code> before the first call of <code><a href="ft2-layer_management.html#ft_get_color_glyph_layer">FT_Get_Color_Glyph_Layer</a></code>.</p>
1125 </td></tr>
1126 </table>
1127
1128 <hr>
1129
1130 <h2 id="ft_get_color_glyph_layer">FT_Get_Color_Glyph_Layer<a class="headerlink" href="#ft_get_color_glyph_layer" title="Permanent link">&para;</a></h2>
1131 <p>Defined in FT_FREETYPE_H (freetype/freetype.h).</p>
1132 <div class = "codehilite"><pre><code>  FT_EXPORT( <a href="ft2-basic_types.html#ft_bool">FT_Bool</a> )
1133   <b>FT_Get_Color_Glyph_Layer</b>( <a href="ft2-base_interface.html#ft_face">FT_Face</a>            face,
1134                             <a href="ft2-basic_types.html#ft_uint">FT_UInt</a>            base_glyph,
1135                             <a href="ft2-basic_types.html#ft_uint">FT_UInt</a>           *aglyph_index,
1136                             <a href="ft2-basic_types.html#ft_uint">FT_UInt</a>           *acolor_index,
1137                             <a href="ft2-layer_management.html#ft_layeriterator">FT_LayerIterator</a>*  iterator );
1138 </code></pre></div>
1139
1140 <p>This is an interface to the &lsquo;COLR&rsquo; table in OpenType fonts to iteratively retrieve the colored glyph layers associated with the current glyph slot.</p>
1141 <p><a href="https://docs.microsoft.com/en-us/typography/opentype/spec/colr">https://docs.microsoft.com/en-us/typography/opentype/spec/colr</a></p>
1142 <p>The glyph layer data for a given glyph index, if present, provides an alternative, multi-color glyph representation: Instead of rendering the outline or bitmap with the given glyph index, glyphs with the indices and colors returned by this function are rendered layer by layer.</p>
1143 <p>The returned elements are ordered in the z&nbsp;direction from bottom to top; the 'n'th element should be rendered with the associated palette color and blended on top of the already rendered layers (elements 0, 1, ..., n-1).</p>
1144 <h4>input</h4>
1145
1146 <table class="fields">
1147 <tr><td class="val" id="face">face</td><td class="desc">
1148 <p>A handle to the parent face object.</p>
1149 </td></tr>
1150 <tr><td class="val" id="base_glyph">base_glyph</td><td class="desc">
1151 <p>The glyph index the colored glyph layers are associated with.</p>
1152 </td></tr>
1153 </table>
1154
1155 <h4>inout</h4>
1156
1157 <table class="fields">
1158 <tr><td class="val" id="iterator">iterator</td><td class="desc">
1159 <p>An <code><a href="ft2-layer_management.html#ft_layeriterator">FT_LayerIterator</a></code> object. For the first call you should set <code>iterator-&gt;p</code> to <code>NULL</code>. For all following calls, simply use the same object again.</p>
1160 </td></tr>
1161 </table>
1162
1163 <h4>output</h4>
1164
1165 <table class="fields">
1166 <tr><td class="val" id="aglyph_index">aglyph_index</td><td class="desc">
1167 <p>The glyph index of the current layer.</p>
1168 </td></tr>
1169 <tr><td class="val" id="acolor_index">acolor_index</td><td class="desc">
1170 <p>The color index into the font face's color palette of the current layer. The value 0xFFFF is special; it doesn't reference a palette entry but indicates that the text foreground color should be used instead (to be set up by the application outside of FreeType).</p>
1171 <p>The color palette can be retrieved with <code><a href="ft2-color_management.html#ft_palette_select">FT_Palette_Select</a></code>.</p>
1172 </td></tr>
1173 </table>
1174
1175 <h4>return</h4>
1176
1177 <p>Value&nbsp;1 if everything is OK. If there are no more layers (or if there are no layers at all), value&nbsp;0 gets returned. In case of an error, value&nbsp;0 is returned also.</p>
1178 <h4>note</h4>
1179
1180 <p>This function is necessary if you want to handle glyph layers by yourself. In particular, functions that operate with <code><a href="ft2-glyph_management.html#ft_glyphrec">FT_GlyphRec</a></code> objects (like <code><a href="ft2-glyph_management.html#ft_get_glyph">FT_Get_Glyph</a></code> or <code><a href="ft2-glyph_management.html#ft_glyph_to_bitmap">FT_Glyph_To_Bitmap</a></code>) don't have access to this information.</p>
1181 <p>Note that <code><a href="ft2-base_interface.html#ft_render_glyph">FT_Render_Glyph</a></code> is able to handle colored glyph layers automatically if the <code><a href="ft2-base_interface.html#ft_load_xxx">FT_LOAD_COLOR</a></code> flag is passed to a previous call to <code><a href="ft2-base_interface.html#ft_load_glyph">FT_Load_Glyph</a></code>. [This is an experimental feature.]</p>
1182 <h4>example</h4>
1183
1184 <div class="highlight"><pre><span></span><code>  FT_Color*         palette;
1185   FT_LayerIterator  iterator;
1186
1187   FT_Bool  have_layers;
1188   FT_UInt  layer_glyph_index;
1189   FT_UInt  layer_color_index;
1190
1191
1192   error = FT_Palette_Select( face, palette_index, &amp;palette );
1193   if ( error )
1194     palette = NULL;
1195
1196   iterator.p  = NULL;
1197   have_layers = FT_Get_Color_Glyph_Layer( face,
1198                                           glyph_index,
1199                                           &amp;layer_glyph_index,
1200                                           &amp;layer_color_index,
1201                                           &amp;iterator );
1202
1203   if ( palette &amp;&amp; have_layers )
1204   {
1205     do
1206     {
1207       FT_Color  layer_color;
1208
1209
1210       if ( layer_color_index == 0xFFFF )
1211         layer_color = text_foreground_color;
1212       else
1213         layer_color = palette[layer_color_index];
1214
1215       // Load and render glyph `layer_glyph_index&#39;, then
1216       // blend resulting pixmap (using color `layer_color&#39;)
1217       // with previously created pixmaps.
1218
1219     } while ( FT_Get_Color_Glyph_Layer( face,
1220                                         glyph_index,
1221                                         &amp;layer_glyph_index,
1222                                         &amp;layer_color_index,
1223                                         &amp;iterator ) );
1224   }
1225 </code></pre></div>
1226
1227 <hr>
1228
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1249           <a href="ft2-color_management.html" title="Glyph Color Management" class="md-flex md-footer-nav__link md-footer-nav__link--prev" rel="prev">
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