1  /****************************************************************************
       2   *
       3   * ftsdf.h
       4   *
       5   *   Signed Distance Field support (specification).
       6   *
       7   * Copyright (C) 2020-2023 by
       8   * David Turner, Robert Wilhelm, and Werner Lemberg.
       9   *
      10   * Written by Anuj Verma.
      11   *
      12   * This file is part of the FreeType project, and may only be used,
      13   * modified, and distributed under the terms of the FreeType project
      14   * license, LICENSE.TXT.  By continuing to use, modify, or distribute
      15   * this file you indicate that you have read the license and
      16   * understand and accept it fully.
      17   *
      18   */
      19  
      20  
      21  #ifndef FTSDF_H_
      22  #define FTSDF_H_
      23  
      24  #include <ft2build.h>
      25  #include FT_CONFIG_CONFIG_H
      26  #include <freetype/ftimage.h>
      27  
      28  /* common properties and function */
      29  #include "ftsdfcommon.h"
      30  
      31  FT_BEGIN_HEADER
      32  
      33    /**************************************************************************
      34     *
      35     * @struct:
      36     *   SDF_Raster_Params
      37     *
      38     * @description:
      39     *   This struct must be passed to the raster render function
      40     *   @FT_Raster_RenderFunc instead of @FT_Raster_Params because the
      41     *   rasterizer requires some additional information to render properly.
      42     *
      43     * @fields:
      44     *   root ::
      45     *     The native raster parameters structure.
      46     *
      47     *   spread ::
      48     *     This is an essential parameter/property required by the renderer.
      49     *     `spread` defines the maximum unsigned value that is present in the
      50     *     final SDF output.  For the default value check file
      51     *     `ftsdfcommon.h`.
      52     *
      53     *   flip_sign ::
      54     *     By default positive values indicate positions inside of contours,
      55     *     i.e., filled by a contour.  If this property is true then that
      56     *     output will be the opposite of the default, i.e., negative values
      57     *     indicate positions inside of contours.
      58     *
      59     *   flip_y ::
      60     *     Setting this parameter to true maked the output image flipped
      61     *     along the y-axis.
      62     *
      63     *   overlaps ::
      64     *     Set this to true to generate SDF for glyphs having overlapping
      65     *     contours.  The overlapping support is limited to glyphs that do not
      66     *     have self-intersecting contours.  Also, removing overlaps require a
      67     *     considerable amount of extra memory; additionally, it will not work
      68     *     if generating SDF from bitmap.
      69     *
      70     * @note:
      71     *   All properties are valid for both the 'sdf' and 'bsdf' renderers; the
      72     *   exception is `overlaps`, which gets ignored by the 'bsdf' renderer.
      73     *
      74     */
      75    typedef struct  SDF_Raster_Params_
      76    {
      77      FT_Raster_Params  root;
      78      FT_UInt           spread;
      79      FT_Bool           flip_sign;
      80      FT_Bool           flip_y;
      81      FT_Bool           overlaps;
      82  
      83    } SDF_Raster_Params;
      84  
      85  
      86    /* rasterizer to convert outline to SDF */
      87    FT_EXPORT_VAR( const FT_Raster_Funcs )  ft_sdf_raster;
      88  
      89    /* rasterizer to convert bitmap to SDF */
      90    FT_EXPORT_VAR( const FT_Raster_Funcs )  ft_bitmap_sdf_raster;
      91  
      92  FT_END_HEADER
      93  
      94  #endif /* FTSDF_H_ */
      95  
      96  
      97  /* END */