ahglyph.c

a very goog book

              FT_Pos  min = seg1->min_coord;
              FT_Pos  max = seg1->max_coord;
              FT_Pos  len, dist, score;


              if ( min < seg2->min_coord )
                min = seg2->min_coord;

              if ( max > seg2->max_coord )
                max = seg2->max_coord;

              len   = max - min;
              dist  = seg2->pos - seg1->pos;
              if ( dist < 0 )
                dist = -dist;

              if ( len < 8 )
                score = 300*8 + dist - len*3;
              else
                score = dist + 300/len;

              if ( score < best_score )
              {
                best_score   = score;
                best_segment = seg2;
              }
            }
          }

        if ( best_segment )
        {
          seg1->link  = best_segment;
          seg1->score = best_score;

          best_segment->num_linked++;
        }


      } /* edges 1 */

      /* now, compute the `serif' segments */
      for ( seg1 = segments; seg1 < segment_limit; seg1++ )
      {
        seg2 = seg1->link;

        if ( seg2 && seg2->link != seg1 )
        {
          seg1->link  = 0;
          seg1->serif = seg2->link;
        }
      }

      ah_setup_uv( outline, ah_uv_fxy );

      segments      = outline->vert_segments;
      segment_limit = segments + outline->num_vsegments;
    }
  }


  static void
  ah_outline_compute_edges( AH_Outline*  outline )
  {
    AH_Edge*      edges;
    AH_Segment*   segments;
    AH_Segment*   segment_limit;
    AH_Direction  up_dir;
    FT_Int*       p_num_edges;
    FT_Int        dimension;
    FT_Fixed      scale;
    FT_Pos        edge_distance_threshold;


    edges         = outline->horz_edges;
    segments      = outline->horz_segments;
    segment_limit = segments + outline->num_hsegments;
    p_num_edges   = &outline->num_hedges;
    up_dir        = ah_dir_right;
    scale         = outline->y_scale;

    for ( dimension = 1; dimension >= 0; dimension-- )
    {
      AH_Edge*     edge;
      AH_Edge*     edge_limit;  /* really == edge + num_edges */
      AH_Segment*  seg;


      /*********************************************************************/
      /*                                                                   */
      /* We will begin by generating a sorted table of edges for the       */
      /* current direction.  To do so, we simply scan each segment and try */
      /* to find an edge in our table that corresponds to its position.    */
      /*                                                                   */
      /* If no edge is found, we create and insert a new edge in the       */
      /* sorted table.  Otherwise, we simply add the segment to the edge's */
      /* list which will be processed in the second step to compute the    */
      /* edge's properties.                                                */
      /*                                                                   */
      /* Note that the edges table is sorted along the segment/edge        */
      /* position.                                                         */
      /*                                                                   */
      /*********************************************************************/

      edge_distance_threshold = FT_MulFix( outline->edge_distance_threshold,
                                           scale );
      if ( edge_distance_threshold > 64 / 4 )
        edge_distance_threshold = 64 / 4;

      edge_limit = edges;
      for ( seg = segments; seg < segment_limit; seg++ )
      {
        AH_Edge*  found = 0;


        /* look for an edge corresponding to the segment */
        for ( edge = edges; edge < edge_limit; edge++ )
        {
          FT_Pos  dist;


          dist = seg->pos - edge->fpos;
          if ( dist < 0 )
            dist = -dist;

          dist = FT_MulFix( dist, scale );
          if ( dist < edge_distance_threshold )
          {
            found = edge;
            break;
          }
        }

        if ( !found )
        {
          /* insert a new edge in the list and */
          /* sort according to the position    */
          while ( edge > edges && edge[-1].fpos > seg->pos )
          {
            edge[0] = edge[-1];
            edge--;
          }
          edge_limit++;

          /* clear all edge fields */
          FT_MEM_SET( edge, 0, sizeof ( *edge ) );

          /* add the segment to the new edge's list */
          edge->first    = seg;
          edge->last     = seg;
          edge->fpos     = seg->pos;
          edge->opos     = edge->pos = FT_MulFix( seg->pos, scale );
          seg->edge_next = seg;
        }
        else
        {
          /* if an edge was found, simply add the segment to the edge's */
          /* list                                                       */
          seg->edge_next        = edge->first;
          edge->last->edge_next = seg;
          edge->last            = seg;
        }
      }

      *p_num_edges = (FT_Int)( edge_limit - edges );


      /*********************************************************************/
      /*                                                                   */
      /* Good, we will now compute each edge's properties according to     */
      /* segments found on its position.  Basically, these are:            */
      /*                                                                   */
      /*  - edge's main direction                                          */
      /*  - stem edge, serif edge or both (which defaults to stem then)    */
      /*  - rounded edge, straigth or both (which defaults to straight)    */
      /*  - link for edge                                                  */
      /*                                                                   */
      /*********************************************************************/

      /* first of all, set the `edge' field in each segment -- this is */
      /* required in order to compute edge links                       */
      for ( edge = edges; edge < edge_limit; edge++ )
      {
        seg = edge->first;
        if ( seg )
          do
          {
            seg->edge = edge;
            seg       = seg->edge_next;
          }
          while ( seg != edge->first );
      }

      /* now, compute each edge properties */
      for ( edge = edges; edge < edge_limit; edge++ )
      {
        int  is_round    = 0;  /* does it contain round segments?    */
        int  is_straight = 0;  /* does it contain straight segments? */
        int  ups         = 0;  /* number of upwards segments         */
        int  downs       = 0;  /* number of downwards segments       */


        seg = edge->first;

        do
        {
          FT_Bool  is_serif;


          /* check for roundness of segment */
          if ( seg->flags & ah_edge_round )
            is_round++;
          else
            is_straight++;

          /* check for segment direction */
          if ( seg->dir == up_dir )
            ups   += seg->max_coord-seg->min_coord;
          else
            downs += seg->max_coord-seg->min_coord;

          /* check for links -- if seg->serif is set, then seg->link must */
          /* be ignored                                                   */
          is_serif = (FT_Bool)( seg->serif && seg->serif->edge != edge );

          if ( seg->link || is_serif )
          {
            AH_Edge*     edge2;
            AH_Segment*  seg2;


            edge2 = edge->link;
            seg2  = seg->link;

            if ( is_serif )
            {
              seg2  = seg->serif;
              edge2 = edge->serif;
            }

            if ( edge2 )
            {
              FT_Pos  edge_delta;
              FT_Pos  seg_delta;


              edge_delta = edge->fpos - edge2->fpos;
              if ( edge_delta < 0 )
                edge_delta = -edge_delta;

              seg_delta = seg->pos - seg2->pos;
              if ( seg_delta < 0 )
                seg_delta = -seg_delta;

              if ( seg_delta < edge_delta )
                edge2 = seg2->edge;
            }
            else
              edge2 = seg2->edge;

            if ( is_serif )
              edge->serif = edge2;
            else
              edge->link  = edge2;
          }

          seg = seg->edge_next;

        } while ( seg != edge->first );

        /* set the round/straight flags */
        edge->flags = ah_edge_normal;

        if ( is_round > 0 && is_round >= is_straight )
          edge->flags |= ah_edge_round;

        /* set the edge's main direction */
        edge->dir = ah_dir_none;

        if ( ups > downs )
          edge->dir = up_dir;

        else if ( ups < downs )
          edge->dir = - up_dir;

        else if ( ups == downs )
          edge->dir = 0;  /* both up and down !! */

        /* gets rid of serifs if link is set                */
        /* XXX: This gets rid of many unpleasant artefacts! */
        /*      Example: the `c' in cour.pfa at size 13     */

        if ( edge->serif && edge->link )
          edge->serif = 0;
      }

      edges         = outline->vert_edges;
      segments      = outline->vert_segments;
      segment_limit = segments + outline->num_vsegments;
      p_num_edges   = &outline->num_vedges;
      up_dir        = ah_dir_up;
      scale         = outline->x_scale;
    }
  }


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    ah_outline_detect_features                                         */
  /*                                                                       */
  /* <Description>                                                         */
  /*    Performs feature detection on a given AH_Outline object.           */
  /*                                                                       */
  FT_LOCAL_DEF( void )
  ah_outline_detect_features( AH_Outline*  outline )
  {
    ah_outline_compute_segments( outline );
    ah_outline_link_segments   ( outline );
    ah_outline_compute_edges   ( outline );
  }


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    ah_outline_compute_blue_edges                                      */
  /*                                                                       */
  /* <Description>                                                         */
  /*    Computes the `blue edges' in a given outline (i.e. those that must */
  /*    be snapped to a blue zone edge (top or bottom).                    */
  /*                                                                       */
  FT_LOCAL_DEF( void )
  ah_outline_compute_blue_edges( AH_Outline*       outline,
                                 AH_Face_Globals*  face_globals )
  {
    AH_Edge*     edge       = outline->horz_edges;
    AH_Edge*     edge_limit = edge + outline->num_hedges;
    AH_Globals*  globals    = &face_globals->design;
    FT_Fixed     y_scale    = outline->y_scale;

    FT_Bool      blue_active[ah_blue_max];


    /* compute which blue zones are active, i.e. have their scaled */
    /* size < 3/4 pixels                                           */
    {
      AH_Blue  blue;
      FT_Bool  check = 0;


      for ( blue = ah_blue_capital_top; blue < ah_blue_max; blue++ )
      {
        FT_Pos  ref, shoot, dist;


        ref   = globals->blue_refs[blue];
        shoot = globals->blue_shoots[blue];
        dist  = ref-shoot;
        if ( dist < 0 )
          dist = -dist;

        blue_active[blue] = 0;

        if ( FT_MulFix( dist, y_scale ) < 48 )
        {
          blue_active[blue] = 1;
          check = 1;
        }
      }

      /* return immediately if no blue zone is active */
      if ( !check )
        return;
    }

    /* compute for each horizontal edge, which blue zone is closer */
    for ( ; edge < edge_limit; edge++ )
    {
      AH_Blue  blue;
      FT_Pos*  best_blue = 0;
      FT_Pos   best_dist;  /* initial threshold */


      /* compute the initial threshold as a fraction of the EM size */
      best_dist = FT_MulFix( face_globals->face->units_per_EM / 40, y_scale );
      if ( best_dist > 64 / 4 )
        best_dist = 64 / 4;

      for ( blue = ah_blue_capital_top; blue < ah_blue_max; blue++ )
      {
        /* if it is a top zone, check for right edges -- if it is a bottom */
        /* zone, check for left edges                                      */
        /*                                                                 */
        /* of course, that's for TrueType XXX                              */
        FT_Bool  is_top_blue  =
                   FT_BOOL( AH_IS_TOP_BLUE( blue ) );
        FT_Bool  is_major_dir =
                   FT_BOOL( edge->dir == outline->horz_major_dir );

        if ( !blue_active[blue] )
          continue;

        /* if it is a top zone, the edge must be against the major    */
        /* direction; if it is a bottom zone, it must be in the major */
        /* direction                                                  */
        if ( is_top_blue ^ is_major_dir )
        {
          FT_Pos   dist;
          FT_Pos*  blue_pos = globals->blue_refs + blue;


          /* first of all, compare it to the reference position */
          dist = edge->fpos - *blue_pos;
          if ( dist < 0 )
            dist = -dist;

          dist = FT_MulFix( dist, y_scale );
          if ( dist < best_dist )
          {
            best_dist = dist;
            best_blue = blue_pos;
          }

          /* now, compare it to the overshoot position if the edge is     */
          /* rounded, and if the edge is over the reference position of a */
          /* top zone, or under the reference position of a bottom zone   */
          if ( edge->flags & ah_edge_round && dist != 0 )
          {
            FT_Bool  is_under_ref = FT_BOOL( edge->fpos < *blue_pos );


            if ( is_top_blue ^ is_under_ref )
            {
              blue_pos = globals->blue_shoots + blue;
              dist = edge->fpos - *blue_pos;
              if ( dist < 0 )
                dist = -dist;

              dist = FT_MulFix( dist, y_scale );
              if ( dist < best_dist )
              {
                best_dist = dist;
                best_blue = blue_pos;
              }
            }
          }
        }
      }

      if ( best_blue )
        edge->blue_edge = best_blue;
    }
  }


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    ah_outline_scale_blue_edges                                        */
  /*                                                                       */
  /* <Description>                                                         */
  /*    This functions must be called before hinting in order to re-adjust */
  /*    the contents of the detected edges (basically change the `blue     */
  /*    edge' pointer from `design units' to `scaled ones').               */
  /*                                                                       */
  FT_LOCAL_DEF( void )
  ah_outline_scale_blue_edges( AH_Outline*       outline,
                               AH_Face_Globals*  globals )
  {
    AH_Edge*  edge       = outline->horz_edges;
    AH_Edge*  edge_limit = edge + outline->num_hedges;
    FT_Int    delta;


    delta = globals->scaled.blue_refs - globals->design.blue_refs;

    for ( ; edge < edge_limit; edge++ )
    {
      if ( edge->blue_edge )
        edge->blue_edge += delta;
    }
  }


/* END */