src/sdf/ftsdfrend.h

/****************************************************************************
 *
 * ftsdfrend.h
 *
 *   Signed Distance Field renderer interface (specification).
 *
 * Copyright (C) 2020-2022 by
 * David Turner, Robert Wilhelm, and Werner Lemberg.
 *
 * Written by Anuj Verma.
 *
 * This file is part of the FreeType project, and may only be used,
 * modified, and distributed under the terms of the FreeType project
 * license, LICENSE.TXT.  By continuing to use, modify, or distribute
 * this file you indicate that you have read the license and
 * understand and accept it fully.
 *
 */


#ifndef FTSDFREND_H_
#define FTSDFREND_H_

#include <freetype/ftrender.h>
#include <freetype/ftmodapi.h>
#include <freetype/internal/ftobjs.h>

FT_BEGIN_HEADER


  /**************************************************************************
   *
   * @struct:
   *   SDF_Renderer_Module
   *
   * @description:
   *   This struct extends the native renderer struct `FT_RendererRec`.  It
   *   is basically used to store various parameters required by the
   *   renderer and some additional parameters that can be used to tweak the
   *   output of the renderer.
   *
   * @fields:
   *   root ::
   *     The native rendere struct.
   *
   *   spread ::
   *     This is an essential parameter/property required by the renderer.
   *     `spread` defines the maximum unsigned value that is present in the
   *     final SDF output.  For the default value check file
   *     `ftsdfcommon.h`.
   *
   *   flip_sign ::
   *     By default positive values indicate positions inside of contours,
   *     i.e., filled by a contour.  If this property is true then that
   *     output will be the opposite of the default, i.e., negative values
   *     indicate positions inside of contours.
   *
   *   flip_y ::
   *     Setting this parameter to true makes the output image flipped
   *     along the y-axis.
   *
   *   overlaps ::
   *     Set this to true to generate SDF for glyphs having overlapping
   *     contours.  The overlapping support is limited to glyphs that do not
   *     have self-intersecting contours.  Also, removing overlaps require a
   *     considerable amount of extra memory; additionally, it will not work
   *     if generating SDF from bitmap.
   *
   * @note:
   *   All properties except `overlaps` are valid for both the 'sdf' and
   *   'bsdf' renderers.
   *
   */
  typedef struct  SDF_Renderer_Module_
  {
    FT_RendererRec  root;
    FT_UInt         spread;
    FT_Bool         flip_sign;
    FT_Bool         flip_y;
    FT_Bool         overlaps;

  } SDF_Renderer_Module, *SDF_Renderer;


  /**************************************************************************
   *
   * @renderer:
   *   ft_sdf_renderer_class
   *
   * @description:
   *   Renderer to convert @FT_Outline to signed distance fields.
   *
   */
  FT_DECLARE_RENDERER( ft_sdf_renderer_class )


  /**************************************************************************
   *
   * @renderer:
   *   ft_bitmap_sdf_renderer_class
   *
   * @description:
   *   This is not exactly a renderer; it is just a converter that
   *   transforms bitmaps to signed distance fields.
   *
   * @note:
   *   This is not a separate module, it is part of the 'sdf' module.
   *
   */
  FT_DECLARE_RENDERER( ft_bitmap_sdf_renderer_class )


FT_END_HEADER

#endif /* FTSDFREND_H_ */


/* END */