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107 <div class="md-flex__cell md-flex__cell--shrink"> 108 <label class="md-icon md-icon--menu md-header-nav__button" for="__drawer"></label> 109 </div> 110 <div class="md-flex__cell md-flex__cell--stretch"> 111 <div class="md-flex__ellipsis md-header-nav__title" data-md-component="title"> 112 113 <span class="md-header-nav__topic"> 114 FreeType-2.10.4 API Reference 115 </span> 116 <span class="md-header-nav__topic"> 117 118 Subpixel Rendering 119 120 </span> 121 122 </div> 123 </div> 124 <div class="md-flex__cell md-flex__cell--shrink"> 125 126 <label class="md-icon md-icon--search md-header-nav__button" for="__search"></label> 127 128<div class="md-search" data-md-component="search" role="dialog"> 129 <label class="md-search__overlay" for="__search"></label> 130 <div class="md-search__inner" role="search"> 131 <form class="md-search__form" name="search"> 132 <input type="text" class="md-search__input" aria-label="search" name="query" placeholder="Search" autocapitalize="off" autocorrect="off" autocomplete="off" spellcheck="false" data-md-component="query" data-md-state="active"> 133 <label class="md-icon md-search__icon" for="__search"></label> 134 <button type="reset" class="md-icon md-search__icon" data-md-component="reset" tabindex="-1"> 135  136 </button> 137 </form> 138 <div class="md-search__output"> 139 <div class="md-search__scrollwrap" data-md-scrollfix> 140 <div class="md-search-result" data-md-component="result"> 141 <div class="md-search-result__meta"> 142 Type to start searching 143 </div> 144 <ol class="md-search-result__list"></ol> 145 </div> 146 </div> 147 </div> 148 </div> 149</div> 150 151 </div> 152 153 </div> 154 </nav> 155</header> 156 157 <div class="md-container"> 158 159 160 161 162 <main class="md-main" role="main"> 163 <div class="md-main__inner md-grid" data-md-component="container"> 164 165 166 <div class="md-sidebar md-sidebar--primary" data-md-component="navigation"> 167 <div class="md-sidebar__scrollwrap"> 168 <div class="md-sidebar__inner"> 169 <nav class="md-nav md-nav--primary" data-md-level="0"> 170 <label class="md-nav__title md-nav__title--site" for="__drawer"> 171 <a href="." title="FreeType-2.10.4 API Reference" class="md-nav__button md-logo"> 172 173 <img alt="logo" src="images/favico.ico" width="48" height="48"> 174 175 </a> 176 FreeType-2.10.4 API Reference 177 </label> 178 179 <ul class="md-nav__list" data-md-scrollfix> 180 181 182 183 184 185 186 <li class="md-nav__item"> 187 <a href="index.html" title="TOC" class="md-nav__link"> 188 TOC 189 </a> 190 </li> 191 192 193 194 195 196 197 198 <li class="md-nav__item"> 199 <a href="ft2-index.html" title="Index" class="md-nav__link"> 200 Index 201 </a> 202 </li> 203 204 205 206 207 208 209 210 <li class="md-nav__item md-nav__item--nested"> 211 212 <input class="md-toggle md-nav__toggle" data-md-toggle="nav-3" type="checkbox" id="nav-3"> 213 214 <label class="md-nav__link" for="nav-3"> 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> 246 247 248 </ul> 249 </nav> 250 </li> 251 252 253 254 255 256 257 258 <li class="md-nav__item md-nav__item--nested"> 259 260 <input class="md-toggle md-nav__toggle" data-md-toggle="nav-4" type="checkbox" id="nav-4"> 261 262 <label class="md-nav__link" for="nav-4"> 263 Core API 264 </label> 265 <nav class="md-nav" data-md-component="collapsible" data-md-level="1"> 266 <label class="md-nav__title" for="nav-4"> 267 Core API 268 </label> 269 <ul class="md-nav__list" data-md-scrollfix> 270 271 272 273 274 275 276 277 <li class="md-nav__item"> 278 <a href="ft2-version.html" title="FreeType Version" class="md-nav__link"> 279 FreeType Version 280 </a> 281 </li> 282 283 284 285 286 287 288 289 <li class="md-nav__item"> 290 <a href="ft2-basic_types.html" title="Basic Data Types" class="md-nav__link"> 291 Basic Data Types 292 </a> 293 </li> 294 295 296 297 298 299 300 301 <li class="md-nav__item"> 302 <a href="ft2-base_interface.html" title="Base Interface" class="md-nav__link"> 303 Base Interface 304 </a> 305 </li> 306 307 308 309 310 311 312 313 <li class="md-nav__item"> 314 <a href="ft2-glyph_variants.html" title="Unicode Variation Sequences" class="md-nav__link"> 315 Unicode Variation Sequences 316 </a> 317 </li> 318 319 320 321 322 323 324 325 <li class="md-nav__item"> 326 <a href="ft2-color_management.html" title="Glyph Color Management" class="md-nav__link"> 327 Glyph Color Management 328 </a> 329 </li> 330 331 332 333 334 335 336 337 <li class="md-nav__item"> 338 <a href="ft2-layer_management.html" title="Glyph Layer Management" class="md-nav__link"> 339 Glyph Layer Management 340 </a> 341 </li> 342 343 344 345 346 347 348 349 <li class="md-nav__item"> 350 <a href="ft2-glyph_management.html" title="Glyph Management" class="md-nav__link"> 351 Glyph Management 352 </a> 353 </li> 354 355 356 357 358 359 360 361 <li class="md-nav__item"> 362 <a href="ft2-mac_specific.html" title="Mac Specific Interface" class="md-nav__link"> 363 Mac Specific Interface 364 </a> 365 </li> 366 367 368 369 370 371 372 373 <li class="md-nav__item"> 374 <a href="ft2-sizes_management.html" title="Size Management" class="md-nav__link"> 375 Size Management 376 </a> 377 </li> 378 379 380 381 382 383 384 385 <li class="md-nav__item"> 386 <a href="ft2-header_file_macros.html" title="Header File Macros" class="md-nav__link"> 387 Header File Macros 388 </a> 389 </li> 390 391 392 </ul> 393 </nav> 394 </li> 395 396 397 398 399 400 401 402 <li class="md-nav__item md-nav__item--nested"> 403 404 <input class="md-toggle md-nav__toggle" data-md-toggle="nav-5" type="checkbox" id="nav-5"> 405 406 <label class="md-nav__link" for="nav-5"> 407 Format-Specific API 408 </label> 409 <nav class="md-nav" data-md-component="collapsible" data-md-level="1"> 410 <label class="md-nav__title" for="nav-5"> 411 Format-Specific API 412 </label> 413 <ul class="md-nav__list" data-md-scrollfix> 414 415 416 417 418 419 420 421 <li class="md-nav__item"> 422 <a href="ft2-multiple_masters.html" title="Multiple Masters" class="md-nav__link"> 423 Multiple Masters 424 </a> 425 </li> 426 427 428 429 430 431 432 433 <li class="md-nav__item"> 434 <a href="ft2-truetype_tables.html" title="TrueType Tables" class="md-nav__link"> 435 TrueType Tables 436 </a> 437 </li> 438 439 440 441 442 443 444 445 <li class="md-nav__item"> 446 <a href="ft2-type1_tables.html" title="Type 1 Tables" class="md-nav__link"> 447 Type 1 Tables 448 </a> 449 </li> 450 451 452 453 454 455 456 457 <li class="md-nav__item"> 458 <a href="ft2-sfnt_names.html" title="SFNT Names" class="md-nav__link"> 459 SFNT Names 460 </a> 461 </li> 462 463 464 465 466 467 468 469 <li class="md-nav__item"> 470 <a href="ft2-bdf_fonts.html" title="BDF and PCF Files" class="md-nav__link"> 471 BDF and PCF Files 472 </a> 473 </li> 474 475 476 477 478 479 480 481 <li class="md-nav__item"> 482 <a href="ft2-cid_fonts.html" title="CID Fonts" class="md-nav__link"> 483 CID Fonts 484 </a> 485 </li> 486 487 488 489 490 491 492 493 <li class="md-nav__item"> 494 <a href="ft2-pfr_fonts.html" title="PFR Fonts" class="md-nav__link"> 495 PFR Fonts 496 </a> 497 </li> 498 499 500 501 502 503 504 505 <li class="md-nav__item"> 506 <a href="ft2-winfnt_fonts.html" title="Window FNT Files" class="md-nav__link"> 507 Window FNT Files 508 </a> 509 </li> 510 511 512 513 514 515 516 517 <li class="md-nav__item"> 518 <a href="ft2-font_formats.html" title="Font Formats" class="md-nav__link"> 519 Font Formats 520 </a> 521 </li> 522 523 524 525 526 527 528 529 <li class="md-nav__item"> 530 <a href="ft2-gasp_table.html" title="Gasp Table" class="md-nav__link"> 531 Gasp Table 532 </a> 533 </li> 534 535 536 </ul> 537 </nav> 538 </li> 539 540 541 542 543 544 545 546 547 548 <li class="md-nav__item md-nav__item--active md-nav__item--nested"> 549 550 <input class="md-toggle md-nav__toggle" data-md-toggle="nav-6" type="checkbox" id="nav-6" checked> 551 552 <label class="md-nav__link" for="nav-6"> 553 Controlling FreeType Modules 554 </label> 555 <nav class="md-nav" data-md-component="collapsible" data-md-level="1"> 556 <label class="md-nav__title" for="nav-6"> 557 Controlling FreeType Modules 558 </label> 559 <ul class="md-nav__list" data-md-scrollfix> 560 561 562 563 564 565 566 567 <li class="md-nav__item"> 568 <a href="ft2-auto_hinter.html" title="The auto-hinter" class="md-nav__link"> 569 The auto-hinter 570 </a> 571 </li> 572 573 574 575 576 577 578 579 <li class="md-nav__item"> 580 <a href="ft2-cff_driver.html" title="The CFF driver" class="md-nav__link"> 581 The CFF driver 582 </a> 583 </li> 584 585 586 587 588 589 590 591 <li class="md-nav__item"> 592 <a href="ft2-t1_cid_driver.html" title="The Type 1 and CID drivers" class="md-nav__link"> 593 The Type 1 and CID drivers 594 </a> 595 </li> 596 597 598 599 600 601 602 603 <li class="md-nav__item"> 604 <a href="ft2-tt_driver.html" title="The TrueType driver" class="md-nav__link"> 605 The TrueType driver 606 </a> 607 </li> 608 609 610 611 612 613 614 615 <li class="md-nav__item"> 616 <a href="ft2-pcf_driver.html" title="The PCF driver" class="md-nav__link"> 617 The PCF driver 618 </a> 619 </li> 620 621 622 623 624 625 626 627 <li class="md-nav__item"> 628 <a href="ft2-properties.html" title="Driver properties" class="md-nav__link"> 629 Driver properties 630 </a> 631 </li> 632 633 634 635 636 637 638 639 <li class="md-nav__item"> 640 <a href="ft2-parameter_tags.html" title="Parameter Tags" class="md-nav__link"> 641 Parameter Tags 642 </a> 643 </li> 644 645 646 647 648 649 650 651 652 653 <li class="md-nav__item md-nav__item--active"> 654 655 <input class="md-toggle md-nav__toggle" data-md-toggle="toc" type="checkbox" id="__toc"> 656 657 658 659 660 <label class="md-nav__link md-nav__link--active" for="__toc"> 661 Subpixel Rendering 662 </label> 663 664 <a href="ft2-lcd_rendering.html" title="Subpixel Rendering" class="md-nav__link md-nav__link--active"> 665 Subpixel Rendering 666 </a> 667 668 669<nav class="md-nav md-nav--secondary"> 670 671 672 673 674 675 <label class="md-nav__title" for="__toc">Table of contents</label> 676 <ul class="md-nav__list" data-md-scrollfix> 677 678 <li class="md-nav__item"> 679 <a href="#synopsis" class="md-nav__link"> 680 Synopsis 681 </a> 682 683</li> 684 685 <li class="md-nav__item"> 686 <a href="#ft_lcdfilter" class="md-nav__link"> 687 FT_LcdFilter 688 </a> 689 690</li> 691 692 <li class="md-nav__item"> 693 <a href="#ft_library_setlcdfilter" class="md-nav__link"> 694 FT_Library_SetLcdFilter 695 </a> 696 697</li> 698 699 <li class="md-nav__item"> 700 <a href="#ft_library_setlcdfilterweights" class="md-nav__link"> 701 FT_Library_SetLcdFilterWeights 702 </a> 703 704</li> 705 706 <li class="md-nav__item"> 707 <a href="#ft_lcdfivetapfilter" class="md-nav__link"> 708 FT_LcdFiveTapFilter 709 </a> 710 711</li> 712 713 <li class="md-nav__item"> 714 <a href="#ft_library_setlcdgeometry" class="md-nav__link"> 715 FT_Library_SetLcdGeometry 716 </a> 717 718</li> 719 720 721 722 723 724 </ul> 725 726</nav> 727 728 </li> 729 730 731 </ul> 732 </nav> 733 </li> 734 735 736 737 738 739 740 741 <li class="md-nav__item md-nav__item--nested"> 742 743 <input class="md-toggle md-nav__toggle" data-md-toggle="nav-7" type="checkbox" id="nav-7"> 744 745 <label class="md-nav__link" for="nav-7"> 746 Cache Sub-System 747 </label> 748 <nav class="md-nav" data-md-component="collapsible" data-md-level="1"> 749 <label class="md-nav__title" for="nav-7"> 750 Cache Sub-System 751 </label> 752 <ul class="md-nav__list" data-md-scrollfix> 753 754 755 756 757 758 759 760 <li class="md-nav__item"> 761 <a href="ft2-cache_subsystem.html" title="Cache Sub-System" class="md-nav__link"> 762 Cache Sub-System 763 </a> 764 </li> 765 766 767 </ul> 768 </nav> 769 </li> 770 771 772 773 774 775 776 777 <li class="md-nav__item md-nav__item--nested"> 778 779 <input class="md-toggle md-nav__toggle" data-md-toggle="nav-8" type="checkbox" id="nav-8"> 780 781 <label class="md-nav__link" for="nav-8"> 782 Support API 783 </label> 784 <nav class="md-nav" data-md-component="collapsible" data-md-level="1"> 785 <label class="md-nav__title" for="nav-8"> 786 Support API 787 </label> 788 <ul class="md-nav__list" data-md-scrollfix> 789 790 791 792 793 794 795 796 <li class="md-nav__item"> 797 <a href="ft2-computations.html" title="Computations" class="md-nav__link"> 798 Computations 799 </a> 800 </li> 801 802 803 804 805 806 807 808 <li class="md-nav__item"> 809 <a href="ft2-list_processing.html" title="List Processing" class="md-nav__link"> 810 List Processing 811 </a> 812 </li> 813 814 815 816 817 818 819 820 <li class="md-nav__item"> 821 <a href="ft2-outline_processing.html" title="Outline Processing" class="md-nav__link"> 822 Outline Processing 823 </a> 824 </li> 825 826 827 828 829 830 831 832 <li class="md-nav__item"> 833 <a href="ft2-quick_advance.html" title="Quick retrieval of advance values" class="md-nav__link"> 834 Quick retrieval of advance values 835 </a> 836 </li> 837 838 839 840 841 842 843 844 <li class="md-nav__item"> 845 <a href="ft2-bitmap_handling.html" title="Bitmap Handling" class="md-nav__link"> 846 Bitmap Handling 847 </a> 848 </li> 849 850 851 852 853 854 855 856 <li class="md-nav__item"> 857 <a href="ft2-raster.html" title="Scanline Converter" class="md-nav__link"> 858 Scanline Converter 859 </a> 860 </li> 861 862 863 864 865 866 867 868 <li class="md-nav__item"> 869 <a href="ft2-glyph_stroker.html" title="Glyph Stroker" class="md-nav__link"> 870 Glyph Stroker 871 </a> 872 </li> 873 874 875 876 877 878 879 880 <li class="md-nav__item"> 881 <a href="ft2-system_interface.html" title="System Interface" class="md-nav__link"> 882 System Interface 883 </a> 884 </li> 885 886 887 888 889 890 891 892 <li class="md-nav__item"> 893 <a href="ft2-module_management.html" title="Module Management" class="md-nav__link"> 894 Module Management 895 </a> 896 </li> 897 898 899 900 901 902 903 904 <li class="md-nav__item"> 905 <a href="ft2-gzip.html" title="GZIP Streams" class="md-nav__link"> 906 GZIP Streams 907 </a> 908 </li> 909 910 911 912 913 914 915 916 <li class="md-nav__item"> 917 <a href="ft2-lzw.html" title="LZW Streams" class="md-nav__link"> 918 LZW Streams 919 </a> 920 </li> 921 922 923 924 925 926 927 928 <li class="md-nav__item"> 929 <a href="ft2-bzip2.html" title="BZIP2 Streams" class="md-nav__link"> 930 BZIP2 Streams 931 </a> 932 </li> 933 934 935 </ul> 936 </nav> 937 </li> 938 939 940 941 942 943 944 945 <li class="md-nav__item md-nav__item--nested"> 946 947 <input class="md-toggle md-nav__toggle" data-md-toggle="nav-9" type="checkbox" id="nav-9"> 948 949 <label class="md-nav__link" for="nav-9"> 950 Error Codes 951 </label> 952 <nav class="md-nav" data-md-component="collapsible" data-md-level="1"> 953 <label class="md-nav__title" for="nav-9"> 954 Error Codes 955 </label> 956 <ul class="md-nav__list" data-md-scrollfix> 957 958 959 960 961 962 963 964 <li class="md-nav__item"> 965 <a href="ft2-error_enumerations.html" title="Error Enumerations" class="md-nav__link"> 966 Error Enumerations 967 </a> 968 </li> 969 970 971 972 973 974 975 976 <li class="md-nav__item"> 977 <a href="ft2-error_code_values.html" title="Error Code Values" class="md-nav__link"> 978 Error Code Values 979 </a> 980 </li> 981 982 983 </ul> 984 </nav> 985 </li> 986 987 988 989 990 991 992 993 <li class="md-nav__item md-nav__item--nested"> 994 995 <input class="md-toggle md-nav__toggle" data-md-toggle="nav-10" type="checkbox" id="nav-10"> 996 997 <label class="md-nav__link" for="nav-10"> 998 Miscellaneous 999 </label> 1000 <nav class="md-nav" data-md-component="collapsible" data-md-level="1"> 1001 <label class="md-nav__title" for="nav-10"> 1002 Miscellaneous 1003 </label> 1004 <ul class="md-nav__list" data-md-scrollfix> 1005 1006 1007 1008 1009 1010 1011 1012 <li class="md-nav__item"> 1013 <a href="ft2-gx_validation.html" title="TrueTypeGX/AAT Validation" class="md-nav__link"> 1014 TrueTypeGX/AAT Validation 1015 </a> 1016 </li> 1017 1018 1019 1020 1021 1022 1023 1024 <li class="md-nav__item"> 1025 <a href="ft2-incremental.html" title="Incremental Loading" class="md-nav__link"> 1026 Incremental Loading 1027 </a> 1028 </li> 1029 1030 1031 1032 1033 1034 1035 1036 <li class="md-nav__item"> 1037 <a href="ft2-truetype_engine.html" title="The TrueType Engine" class="md-nav__link"> 1038 The TrueType Engine 1039 </a> 1040 </li> 1041 1042 1043 1044 1045 1046 1047 1048 <li class="md-nav__item"> 1049 <a href="ft2-ot_validation.html" title="OpenType Validation" class="md-nav__link"> 1050 OpenType Validation 1051 </a> 1052 </li> 1053 1054 1055 </ul> 1056 </nav> 1057 </li> 1058 1059 1060 </ul> 1061</nav> 1062 </div> 1063 </div> 1064 </div> 1065 1066 1067 <div class="md-sidebar md-sidebar--secondary" data-md-component="toc"> 1068 <div class="md-sidebar__scrollwrap"> 1069 <div class="md-sidebar__inner"> 1070 1071<nav class="md-nav md-nav--secondary"> 1072 1073 1074 1075 1076 1077 <label class="md-nav__title" for="__toc">Table of contents</label> 1078 <ul class="md-nav__list" data-md-scrollfix> 1079 1080 <li class="md-nav__item"> 1081 <a href="#synopsis" class="md-nav__link"> 1082 Synopsis 1083 </a> 1084 1085</li> 1086 1087 <li class="md-nav__item"> 1088 <a href="#ft_lcdfilter" class="md-nav__link"> 1089 FT_LcdFilter 1090 </a> 1091 1092</li> 1093 1094 <li class="md-nav__item"> 1095 <a href="#ft_library_setlcdfilter" class="md-nav__link"> 1096 FT_Library_SetLcdFilter 1097 </a> 1098 1099</li> 1100 1101 <li class="md-nav__item"> 1102 <a href="#ft_library_setlcdfilterweights" class="md-nav__link"> 1103 FT_Library_SetLcdFilterWeights 1104 </a> 1105 1106</li> 1107 1108 <li class="md-nav__item"> 1109 <a href="#ft_lcdfivetapfilter" class="md-nav__link"> 1110 FT_LcdFiveTapFilter 1111 </a> 1112 1113</li> 1114 1115 <li class="md-nav__item"> 1116 <a href="#ft_library_setlcdgeometry" class="md-nav__link"> 1117 FT_Library_SetLcdGeometry 1118 </a> 1119 1120</li> 1121 1122 1123 1124 1125 1126 </ul> 1127 1128</nav> 1129 </div> 1130 </div> 1131 </div> 1132 1133 1134 <div class="md-content"> 1135 <article class="md-content__inner md-typeset"> 1136 1137 1138 1139 <p><a href="https://www.freetype.org">FreeType</a> » <a href="../">Docs</a> » <a href="index.html#controlling-freetype-modules">Controlling FreeType Modules</a> » Subpixel Rendering</p> 1140<hr /> 1141<h1 id="subpixel-rendering">Subpixel Rendering<a class="headerlink" href="#subpixel-rendering" title="Permanent link">¶</a></h1> 1142<h2 id="synopsis">Synopsis<a class="headerlink" href="#synopsis" title="Permanent link">¶</a></h2> 1143<p>FreeType provides two alternative subpixel rendering technologies. Should you define <code>FT_CONFIG_OPTION_SUBPIXEL_RENDERING</code> in your <code>ftoption.h</code> file, this enables ClearType-style rendering. Otherwise, Harmony LCD rendering is enabled. These technologies are controlled differently and API described below, although always available, performs its function when appropriate method is enabled and does nothing otherwise.</p> 1144<p>ClearType-style LCD rendering exploits the color-striped structure of LCD pixels, increasing the available resolution in the direction of the stripe (usually horizontal RGB) by a factor of 3. Using the subpixels coverages unfiltered can create severe color fringes especially when rendering thin features. Indeed, to produce black-on-white text, the nearby color subpixels must be dimmed equally.</p> 1145<p>A good 5-tap FIR filter should be applied to subpixel coverages regardless of pixel boundaries and should have these properties:</p> 1146<ol> 1147<li> 1148<p>It should be symmetrical, like { a, b, c, b, a }, to avoid any shifts in appearance.</p> 1149</li> 1150<li> 1151<p>It should be color-balanced, meaning a + b = c, to reduce color fringes by distributing the computed coverage for one subpixel to all subpixels equally.</p> 1152</li> 1153<li> 1154<p>It should be normalized, meaning 2a + 2b + c = 1.0 to maintain overall brightness.</p> 1155</li> 1156</ol> 1157<p>Boxy 3-tap filter {0, ⅓, ⅓, ⅓, 0} is sharper but is less forgiving of non-ideal gamma curves of a screen (and viewing angles), beveled filters are fuzzier but more tolerant.</p> 1158<p>Use the <code><a href="ft2-lcd_rendering.html#ft_library_setlcdfilter">FT_Library_SetLcdFilter</a></code> or <code><a href="ft2-lcd_rendering.html#ft_library_setlcdfilterweights">FT_Library_SetLcdFilterWeights</a></code> API to specify a low-pass filter, which is then applied to subpixel-rendered bitmaps generated through <code><a href="ft2-base_interface.html#ft_render_glyph">FT_Render_Glyph</a></code>.</p> 1159<p>Harmony LCD rendering is suitable to panels with any regular subpixel structure, not just monitors with 3 color striped subpixels, as long as the color subpixels have fixed positions relative to the pixel center. In this case, each color channel is then rendered separately after shifting the outline opposite to the subpixel shift so that the coverage maps are aligned. This method is immune to color fringes because the shifts do not change integral coverage.</p> 1160<p>The subpixel geometry must be specified by xy-coordinates for each subpixel. By convention they may come in the RGB order: {{-⅓, 0}, {0, 0}, {⅓, 0}} for standard RGB striped panel or {{-⅙, ¼}, {-⅙, -¼}, {⅓, 0}} for a certain PenTile panel.</p> 1161<p>Use the <code><a href="ft2-lcd_rendering.html#ft_library_setlcdgeometry">FT_Library_SetLcdGeometry</a></code> API to specify subpixel positions. If one follows the RGB order convention, the same order applies to the resulting <code><a href="ft2-basic_types.html#ft_pixel_mode">FT_PIXEL_MODE_LCD</a></code> and <code><a href="ft2-basic_types.html#ft_pixel_mode">FT_PIXEL_MODE_LCD_V</a></code> bitmaps. Note, however, that the coordinate frame for the latter must be rotated clockwise. Harmony with default LCD geometry is equivalent to ClearType with light filter.</p> 1162<p>As a result of ClearType filtering or Harmony rendering, the dimensions of LCD bitmaps can be either wider or taller than the dimensions of the corresponding outline with regard to the pixel grid. For example, for <code><a href="ft2-base_interface.html#ft_render_mode">FT_RENDER_MODE_LCD</a></code>, the filter adds 2 subpixels to the left, and 2 subpixels to the right. The bitmap offset values are adjusted accordingly, so clients shouldn't need to modify their layout and glyph positioning code when enabling the filter.</p> 1163<p>The ClearType and Harmony rendering is applicable to glyph bitmaps rendered through <code><a href="ft2-base_interface.html#ft_render_glyph">FT_Render_Glyph</a></code>, <code><a href="ft2-base_interface.html#ft_load_glyph">FT_Load_Glyph</a></code>, <code><a href="ft2-base_interface.html#ft_load_char">FT_Load_Char</a></code>, and <code><a href="ft2-glyph_management.html#ft_glyph_to_bitmap">FT_Glyph_To_Bitmap</a></code>, when <code><a href="ft2-base_interface.html#ft_render_mode">FT_RENDER_MODE_LCD</a></code> or <code><a href="ft2-base_interface.html#ft_render_mode">FT_RENDER_MODE_LCD_V</a></code> is specified. This API does not control <code><a href="ft2-outline_processing.html#ft_outline_render">FT_Outline_Render</a></code> and <code><a href="ft2-outline_processing.html#ft_outline_get_bitmap">FT_Outline_Get_Bitmap</a></code>.</p> 1164<p>The described algorithms can completely remove color artefacts when combined with gamma-corrected alpha blending in linear space. Each of the 3 alpha values (subpixels) must by independently used to blend one color channel. That is, red alpha blends the red channel of the text color with the red channel of the background pixel.</p> 1165<h2 id="ft_lcdfilter">FT_LcdFilter<a class="headerlink" href="#ft_lcdfilter" title="Permanent link">¶</a></h2> 1166<p>Defined in FT_LCD_FILTER_H (freetype/ftlcdfil.h).</p> 1167<div class = "codehilite"><pre><code> <span class="keyword">typedef</span> <span class="keyword">enum</span> FT_LcdFilter_ 1168 { 1169 <a href="ft2-lcd_rendering.html#ft_lcd_filter_none">FT_LCD_FILTER_NONE</a> = 0, 1170 <a href="ft2-lcd_rendering.html#ft_lcd_filter_default">FT_LCD_FILTER_DEFAULT</a> = 1, 1171 <a href="ft2-lcd_rendering.html#ft_lcd_filter_light">FT_LCD_FILTER_LIGHT</a> = 2, 1172 <a href="ft2-lcd_rendering.html#ft_lcd_filter_legacy1">FT_LCD_FILTER_LEGACY1</a> = 3, 1173 <a href="ft2-lcd_rendering.html#ft_lcd_filter_legacy">FT_LCD_FILTER_LEGACY</a> = 16, 1174 1175 FT_LCD_FILTER_MAX /* do not remove */ 1176 1177 } <b>FT_LcdFilter</b>; 1178</code></pre></div> 1179 1180<p>A list of values to identify various types of LCD filters.</p> 1181<h4>values</h4> 1182 1183<table class="fields"> 1184<tr><td class="val" id="ft_lcd_filter_none">FT_LCD_FILTER_NONE</td><td class="desc"> 1185<p>Do not perform filtering. When used with subpixel rendering, this results in sometimes severe color fringes.</p> 1186</td></tr> 1187<tr><td class="val" id="ft_lcd_filter_default">FT_LCD_FILTER_DEFAULT</td><td class="desc"> 1188<p>This is a beveled, normalized, and color-balanced five-tap filter with weights of [0x08 0x4D 0x56 0x4D 0x08] in 1/256th units.</p> 1189</td></tr> 1190<tr><td class="val" id="ft_lcd_filter_light">FT_LCD_FILTER_LIGHT</td><td class="desc"> 1191<p>this is a boxy, normalized, and color-balanced three-tap filter with weights of [0x00 0x55 0x56 0x55 0x00] in 1/256th units.</p> 1192</td></tr> 1193<tr><td class="val" id="ft_lcd_filter_legacy">FT_LCD_FILTER_LEGACY</td><td class="desc"> 1194 1195</td></tr> 1196<tr><td class="val" id="ft_lcd_filter_legacy1">FT_LCD_FILTER_LEGACY1</td><td class="desc"> 1197<p>This filter corresponds to the original libXft color filter. It provides high contrast output but can exhibit really bad color fringes if glyphs are not extremely well hinted to the pixel grid. This filter is only provided for comparison purposes, and might be disabled or stay unsupported in the future. The second value is provided for compatibility with FontConfig, which historically used different enumeration, sometimes incorrectly forwarded to FreeType.</p> 1198</td></tr> 1199</table> 1200 1201<h4>since</h4> 1202 1203<p>2.3.0 (<code>FT_LCD_FILTER_LEGACY1</code> since 2.6.2)</p> 1204<hr> 1205 1206<h2 id="ft_library_setlcdfilter">FT_Library_SetLcdFilter<a class="headerlink" href="#ft_library_setlcdfilter" title="Permanent link">¶</a></h2> 1207<p>Defined in FT_LCD_FILTER_H (freetype/ftlcdfil.h).</p> 1208<div class = "codehilite"><pre><code> FT_EXPORT( <a href="ft2-basic_types.html#ft_error">FT_Error</a> ) 1209 <b>FT_Library_SetLcdFilter</b>( <a href="ft2-base_interface.html#ft_library">FT_Library</a> library, 1210 <a href="ft2-lcd_rendering.html#ft_lcdfilter">FT_LcdFilter</a> filter ); 1211</code></pre></div> 1212 1213<p>This function is used to change filter applied to LCD decimated bitmaps, like the ones used when calling <code><a href="ft2-base_interface.html#ft_render_glyph">FT_Render_Glyph</a></code> with <code><a href="ft2-base_interface.html#ft_render_mode">FT_RENDER_MODE_LCD</a></code> or <code><a href="ft2-base_interface.html#ft_render_mode">FT_RENDER_MODE_LCD_V</a></code>.</p> 1214<h4>input</h4> 1215 1216<table class="fields"> 1217<tr><td class="val" id="library">library</td><td class="desc"> 1218<p>A handle to the target library instance.</p> 1219</td></tr> 1220<tr><td class="val" id="filter">filter</td><td class="desc"> 1221<p>The filter type.</p> 1222<p>You can use <code><a href="ft2-lcd_rendering.html#ft_lcdfilter">FT_LCD_FILTER_NONE</a></code> here to disable this feature, or <code><a href="ft2-lcd_rendering.html#ft_lcdfilter">FT_LCD_FILTER_DEFAULT</a></code> to use a default filter that should work well on most LCD screens.</p> 1223</td></tr> 1224</table> 1225 1226<h4>return</h4> 1227 1228<p>FreeType error code. 0 means success.</p> 1229<h4>note</h4> 1230 1231<p>Since 2.10.3 the LCD filtering is enabled with <code><a href="ft2-lcd_rendering.html#ft_lcdfilter">FT_LCD_FILTER_DEFAULT</a></code>. It is no longer necessary to call this function explicitly except to choose a different filter or disable filtering altogether with <code><a href="ft2-lcd_rendering.html#ft_lcdfilter">FT_LCD_FILTER_NONE</a></code>.</p> 1232<p>This function does nothing but returns <code>FT_Err_Unimplemented_Feature</code> if the configuration macro <code>FT_CONFIG_OPTION_SUBPIXEL_RENDERING</code> is not defined in your build of the library.</p> 1233<h4>since</h4> 1234 1235<p>2.3.0</p> 1236<hr> 1237 1238<h2 id="ft_library_setlcdfilterweights">FT_Library_SetLcdFilterWeights<a class="headerlink" href="#ft_library_setlcdfilterweights" title="Permanent link">¶</a></h2> 1239<p>Defined in FT_LCD_FILTER_H (freetype/ftlcdfil.h).</p> 1240<div class = "codehilite"><pre><code> FT_EXPORT( <a href="ft2-basic_types.html#ft_error">FT_Error</a> ) 1241 <b>FT_Library_SetLcdFilterWeights</b>( <a href="ft2-base_interface.html#ft_library">FT_Library</a> library, 1242 <span class="keyword">unsigned</span> <span class="keyword">char</span> *weights ); 1243</code></pre></div> 1244 1245<p>This function can be used to enable LCD filter with custom weights, instead of using presets in <code><a href="ft2-lcd_rendering.html#ft_library_setlcdfilter">FT_Library_SetLcdFilter</a></code>.</p> 1246<h4>input</h4> 1247 1248<table class="fields"> 1249<tr><td class="val" id="library">library</td><td class="desc"> 1250<p>A handle to the target library instance.</p> 1251</td></tr> 1252<tr><td class="val" id="weights">weights</td><td class="desc"> 1253<p>A pointer to an array; the function copies the first five bytes and uses them to specify the filter weights in 1/256th units.</p> 1254</td></tr> 1255</table> 1256 1257<h4>return</h4> 1258 1259<p>FreeType error code. 0 means success.</p> 1260<h4>note</h4> 1261 1262<p>This function does nothing but returns <code>FT_Err_Unimplemented_Feature</code> if the configuration macro <code>FT_CONFIG_OPTION_SUBPIXEL_RENDERING</code> is not defined in your build of the library.</p> 1263<p>LCD filter weights can also be set per face using <code><a href="ft2-base_interface.html#ft_face_properties">FT_Face_Properties</a></code> with <code><a href="ft2-parameter_tags.html#ft_param_tag_lcd_filter_weights">FT_PARAM_TAG_LCD_FILTER_WEIGHTS</a></code>.</p> 1264<h4>since</h4> 1265 1266<p>2.4.0</p> 1267<hr> 1268 1269<h2 id="ft_lcdfivetapfilter">FT_LcdFiveTapFilter<a class="headerlink" href="#ft_lcdfivetapfilter" title="Permanent link">¶</a></h2> 1270<p>Defined in FT_LCD_FILTER_H (freetype/ftlcdfil.h).</p> 1271<div class = "codehilite"><pre><code>#<span class="keyword">define</span> FT_LCD_FILTER_FIVE_TAPS 5 1272 1273 <span class="keyword">typedef</span> <a href="ft2-basic_types.html#ft_byte">FT_Byte</a> <b>FT_LcdFiveTapFilter</b>[FT_LCD_FILTER_FIVE_TAPS]; 1274</code></pre></div> 1275 1276<p>A typedef for passing the five LCD filter weights to <code><a href="ft2-base_interface.html#ft_face_properties">FT_Face_Properties</a></code> within an <code><a href="ft2-base_interface.html#ft_parameter">FT_Parameter</a></code> structure.</p> 1277<h4>since</h4> 1278 1279<p>2.8</p> 1280<hr> 1281 1282<h2 id="ft_library_setlcdgeometry">FT_Library_SetLcdGeometry<a class="headerlink" href="#ft_library_setlcdgeometry" title="Permanent link">¶</a></h2> 1283<p>Defined in FT_LCD_FILTER_H (freetype/ftlcdfil.h).</p> 1284<div class = "codehilite"><pre><code> FT_EXPORT( <a href="ft2-basic_types.html#ft_error">FT_Error</a> ) 1285 <b>FT_Library_SetLcdGeometry</b>( <a href="ft2-base_interface.html#ft_library">FT_Library</a> library, 1286 <a href="ft2-basic_types.html#ft_vector">FT_Vector</a> sub[3] ); 1287</code></pre></div> 1288 1289<p>This function can be used to modify default positions of color subpixels, which controls Harmony LCD rendering.</p> 1290<h4>input</h4> 1291 1292<table class="fields"> 1293<tr><td class="val" id="library">library</td><td class="desc"> 1294<p>A handle to the target library instance.</p> 1295</td></tr> 1296<tr><td class="val" id="sub">sub</td><td class="desc"> 1297<p>A pointer to an array of 3 vectors in 26.6 fractional pixel format; the function modifies the default values, see the note below.</p> 1298</td></tr> 1299</table> 1300 1301<h4>return</h4> 1302 1303<p>FreeType error code. 0 means success.</p> 1304<h4>note</h4> 1305 1306<p>Subpixel geometry examples:</p> 1307<ul> 1308<li> 1309<p>{{-21, 0}, {0, 0}, {21, 0}} is the default, corresponding to 3 color stripes shifted by a third of a pixel. This could be an RGB panel.</p> 1310</li> 1311<li> 1312<p>{{21, 0}, {0, 0}, {-21, 0}} looks the same as the default but can specify a BGR panel instead, while keeping the bitmap in the same RGB888 format.</p> 1313</li> 1314<li> 1315<p>{{0, 21}, {0, 0}, {0, -21}} is the vertical RGB, but the bitmap stays RGB888 as a result.</p> 1316</li> 1317<li> 1318<p>{{-11, 16}, {-11, -16}, {22, 0}} is a certain PenTile arrangement.</p> 1319</li> 1320</ul> 1321<p>This function does nothing and returns <code>FT_Err_Unimplemented_Feature</code> in the context of ClearType-style subpixel rendering when <code>FT_CONFIG_OPTION_SUBPIXEL_RENDERING</code> is defined in your build of the library.</p> 1322<h4>since</h4> 1323 1324<p>2.10.0</p> 1325<hr> 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 </article> 1337 </div> 1338 </div> 1339 </main> 1340 1341 1342<footer class="md-footer"> 1343 1344 <div class="md-footer-nav"> 1345 <nav class="md-footer-nav__inner md-grid"> 1346 1347 <a href="ft2-parameter_tags.html" title="Parameter Tags" class="md-flex md-footer-nav__link md-footer-nav__link--prev" rel="prev"> 1348 <div class="md-flex__cell md-flex__cell--shrink"> 1349 <i class="md-icon md-icon--arrow-back md-footer-nav__button"></i> 1350 </div> 1351 <div class="md-flex__cell md-flex__cell--stretch md-footer-nav__title"> 1352 <span class="md-flex__ellipsis"> 1353 <span class="md-footer-nav__direction"> 1354 Previous 1355 </span> 1356 Parameter Tags 1357 </span> 1358 </div> 1359 </a> 1360 1361 1362 <a href="ft2-cache_subsystem.html" title="Cache Sub-System" class="md-flex md-footer-nav__link md-footer-nav__link--next" rel="next"> 1363 <div class="md-flex__cell md-flex__cell--stretch md-footer-nav__title"> 1364 <span class="md-flex__ellipsis"> 1365 <span class="md-footer-nav__direction"> 1366 Next 1367 </span> 1368 Cache Sub-System 1369 </span> 1370 </div> 1371 <div class="md-flex__cell md-flex__cell--shrink"> 1372 <i class="md-icon md-icon--arrow-forward md-footer-nav__button"></i> 1373 </div> 1374 </a> 1375 1376 </nav> 1377 </div> 1378 1379 <div class="md-footer-meta md-typeset"> 1380 <div class="md-footer-meta__inner md-grid"> 1381 <div class="md-footer-copyright"> 1382 1383 <div class="md-footer-copyright__highlight"> 1384 Copyright 2020 <a href = "https://www.freetype.org/license.html">The FreeType Project</a>. 1385 </div> 1386 1387 powered by 1388 <a href="https://www.mkdocs.org" target="_blank" rel="noopener">MkDocs</a> 1389 and 1390 <a href="https://squidfunk.github.io/mkdocs-material/" target="_blank" rel="noopener"> 1391 Material for MkDocs</a> 1392 </div> 1393 1394 </div> 1395 </div> 1396</footer> 1397 1398 </div> 1399 1400 <script src="assets/javascripts/application.c33a9706.js"></script> 1401 1402 <script>app.initialize({version:"1.1",url:{base:"."}})</script> 1403 1404 <script src="javascripts/extra.js"></script> 1405 1406 1407 </body> 1408</html>