ahhint.c

下载来的一个看图软件的源代码

/***************************************************************************/
/*                                                                         */
/*  ahhint.c                                                               */
/*                                                                         */
/*    Glyph hinter (body).                                                 */
/*                                                                         */
/*  Copyright 2000-2001, 2002, 2003 Catharon Productions Inc.              */
/*  Author: David Turner                                                   */
/*                                                                         */
/*  This file is part of the Catharon Typography Project and shall only    */
/*  be used, modified, and distributed under the terms of the Catharon     */
/*  Open Source License that should come with this file under the name     */
/*  `CatharonLicense.txt'.  By continuing to use, modify, or distribute    */
/*  this file you indicate that you have read the license and              */
/*  understand and accept it fully.                                        */
/*                                                                         */
/*  Note that this license is compatible with the FreeType license.        */
/*                                                                         */
/***************************************************************************/


#include <ft2build.h>
#include "ahhint.h"
#include "ahglyph.h"
#include "ahangles.h"
#include "aherrors.h"
#include FT_OUTLINE_H


#define FACE_GLOBALS( face )  ( (AH_Face_Globals)(face)->autohint.data )

#define AH_USE_IUP
#define OPTIM_STEM_SNAP


  /*************************************************************************/
  /*************************************************************************/
  /****                                                                 ****/
  /****   Hinting routines                                              ****/
  /****                                                                 ****/
  /*************************************************************************/
  /*************************************************************************/

  /* snap a given width in scaled coordinates to one of the */
  /* current standard widths                                */
  static FT_Pos
  ah_snap_width( FT_Pos*  widths,
                 FT_Int   count,
                 FT_Pos   width )
  {
    int     n;
    FT_Pos  best      = 64 + 32 + 2;
    FT_Pos  reference = width;
    FT_Pos  scaled;


    for ( n = 0; n < count; n++ )
    {
      FT_Pos  w;
      FT_Pos  dist;


      w = widths[n];
      dist = width - w;
      if ( dist < 0 )
        dist = -dist;
      if ( dist < best )
      {
        best      = dist;
        reference = w;
      }
    }

    scaled = ( reference + 32 ) & -64;

    if ( width >= reference )
    {
      if ( width < scaled + 48 )
        width = reference;
    }
    else
    {
      if ( width > scaled - 48 )
        width = reference;
    }

    return width;
  }


  /* compute the snapped width of a given stem */

#ifdef FT_CONFIG_CHESTER_SERIF

  static FT_Pos
  ah_compute_stem_width( AH_Hinter      hinter,
                         int            vertical,
                         FT_Pos         width,
                         AH_Edge_Flags  base_flags,
                         AH_Edge_Flags  stem_flags )
  {
    AH_Globals  globals = &hinter->globals->scaled;
    FT_Pos      dist    = width;
    FT_Int      sign    = 0;


    if ( dist < 0 )
    {
      dist = -width;
      sign = 1;
    }

    if ( !hinter->do_stem_adjust )
    {
      /* leave stem widths unchanged */
    }
    else if ( (  vertical && !hinter->do_vert_snapping ) ||
              ( !vertical && !hinter->do_horz_snapping ) )
    {
      /* smooth hinting process: very lightly quantize the stem width */
      /*                                                              */

      /* leave the widths of serifs alone */

      if ( ( stem_flags & AH_EDGE_SERIF ) && vertical && ( dist < 3 * 64 ) )
        goto Done_Width;

      else if ( ( base_flags & AH_EDGE_ROUND ) )
      {
        if ( dist < 80 )
          dist = 64;
      }
      else if ( dist < 56 )
        dist = 56;

      {
        FT_Pos  delta = dist - globals->stds[vertical];


        if ( delta < 0 )
          delta = -delta;

        if ( delta < 40 )
        {
          dist = globals->stds[vertical];
          if ( dist < 48 )
            dist = 48;

          goto Done_Width;
        }

        if ( dist < 3 * 64 )
        {
          delta  = dist & 63;
          dist  &= -64;

          if ( delta < 10 )
            dist += delta;

          else if ( delta < 32 )
            dist += 10;

          else if ( delta < 54 )
            dist += 54;

          else
            dist += delta;
        }
        else
          dist = ( dist + 32 ) & -64;
      }
    }
    else
    {
      /* strong hinting process: snap the stem width to integer pixels */
      /*                                                               */
      if ( vertical )
      {
        dist = ah_snap_width( globals->heights, globals->num_heights, dist );

        /* in the case of vertical hinting, always round */
        /* the stem heights to integer pixels            */
        if ( dist >= 64 )
          dist = ( dist + 16 ) & -64;
        else
          dist = 64;
      }
      else
      {
        dist = ah_snap_width( globals->widths, globals->num_widths, dist );

        if ( hinter->flags & AH_HINTER_MONOCHROME )
        {
          /* monochrome horizontal hinting: snap widths to integer pixels */
          /* with a different threshold                                   */
          if ( dist < 64 )
            dist = 64;
          else
            dist = ( dist + 32 ) & -64;
        }
        else
        {
          /* for horizontal anti-aliased hinting, we adopt a more subtle */
          /* approach: we strengthen small stems, round stems whose size */
          /* is between 1 and 2 pixels to an integer, otherwise nothing  */
          if ( dist < 48 )
            dist = ( dist + 64 ) >> 1;

          else if ( dist < 128 )
            dist = ( dist + 22 ) & -64;
          else
            /* XXX: round otherwise to prevent color fringes in LCD mode */
            dist = ( dist + 32 ) & -64;
        }
      }
    }

  Done_Width:
    if ( sign )
      dist = -dist;

    return dist;
  }

#else /* !FT_CONFIG_CHESTER_SERIF */

  static FT_Pos
  ah_compute_stem_width( AH_Hinter  hinter,
                         int        vertical,
                         FT_Pos     width )
  {
    AH_Globals  globals = &hinter->globals->scaled;
    FT_Pos      dist    = width;
    FT_Int      sign    = 0;


    if ( dist < 0 )
    {
      dist = -width;
      sign = 1;
    }

    if ( !hinter->do_stem_adjust )
    {
      /* leave stem widths unchanged */
    }
    else if ( (  vertical && !hinter->do_vert_snapping ) ||
              ( !vertical && !hinter->do_horz_snapping ) )
    {
      /* smooth hinting process: very lightly quantize the stem width */
      /*                                                              */
      if ( dist < 64 )
        dist = 64;

      {
        FT_Pos  delta = dist - globals->stds[vertical];


        if ( delta < 0 )
          delta = -delta;

        if ( delta < 40 )
        {
          dist = globals->stds[vertical];
          if ( dist < 48 )
            dist = 48;
        }

        if ( dist < 3 * 64 )
        {
          delta  = dist & 63;
          dist  &= -64;

          if ( delta < 10 )
            dist += delta;

          else if ( delta < 32 )
            dist += 10;

          else if ( delta < 54 )
            dist += 54;

          else
            dist += delta;
        }
        else
          dist = ( dist + 32 ) & -64;
      }
    }
    else
    {
      /* strong hinting process: snap the stem width to integer pixels */
      /*                                                               */
      if ( vertical )
      {
        dist = ah_snap_width( globals->heights, globals->num_heights, dist );

        /* in the case of vertical hinting, always round */
        /* the stem heights to integer pixels            */
        if ( dist >= 64 )
          dist = ( dist + 16 ) & -64;
        else
          dist = 64;
      }
      else
      {
        dist = ah_snap_width( globals->widths, globals->num_widths, dist );

        if ( hinter->flags & AH_HINTER_MONOCHROME )
        {
          /* monochrome horizontal hinting: snap widths to integer pixels */
          /* with a different threshold                                   */
          if ( dist < 64 )
            dist = 64;
          else
            dist = ( dist + 32 ) & -64;
        }
        else
        {
          /* for horizontal anti-aliased hinting, we adopt a more subtle */
          /* approach: we strengthen small stems, round stems whose size */
          /* is between 1 and 2 pixels to an integer, otherwise nothing  */
          if ( dist < 48 )
            dist = ( dist + 64 ) >> 1;

          else if ( dist < 128 )
            dist = ( dist + 22 ) & -64;
          else
            /* XXX: round otherwise to prevent color fringes in LCD mode */
            dist = ( dist + 32 ) & -64;
        }
      }
    }

    if ( sign )
      dist = -dist;

    return dist;
  }

#endif /* !FT_CONFIG_CHESTER_SERIF */


  /* align one stem edge relative to the previous stem edge */
  static void
  ah_align_linked_edge( AH_Hinter  hinter,
                        AH_Edge    base_edge,
                        AH_Edge    stem_edge,
                        int        vertical )
  {
    FT_Pos  dist = stem_edge->opos - base_edge->opos;

#ifdef FT_CONFIG_CHESTER_SERIF

    FT_Pos  fitted_width = ah_compute_stem_width( hinter,
                                                  vertical,
                                                  dist,
                                                  base_edge->flags,
                                                  stem_edge->flags );


    stem_edge->pos = base_edge->pos + fitted_width;

#else

    stem_edge->pos = base_edge->pos +
                     ah_compute_stem_width( hinter, vertical, dist );

#endif

  }


  static void
  ah_align_serif_edge( AH_Hinter  hinter,
                       AH_Edge    base,
                       AH_Edge    serif,
                       int        vertical )
  {
    FT_Pos  dist;
    FT_Pos  sign = 1;

    FT_UNUSED( hinter );
    FT_UNUSED( vertical );


    dist = serif->opos - base->opos;
    if ( dist < 0 )
    {
      dist = -dist;
      sign = -1;
    }

#if 0
    /* do not touch serifs widths! */
    if ( base->flags & AH_EDGE_DONE )
    {
      if ( dist >= 64 )
        dist = ( dist + 8 ) & -64;

      else if ( dist <= 32 && !vertical )
        dist = ( dist + 33 ) >> 1;

      else
        dist = 0;
    }
#endif

    serif->pos = base->pos + sign * dist;
  }


  /*************************************************************************/
  /*************************************************************************/
  /*************************************************************************/
  /****                                                                 ****/
  /****       E D G E   H I N T I N G                                   ****/
  /****                                                                 ****/
  /*************************************************************************/
  /*************************************************************************/
  /*************************************************************************/


  FT_LOCAL_DEF( void )
  ah_hinter_hint_edges( AH_Hinter  hinter )
  {
    AH_Edge     edges;
    AH_Edge     edge_limit;
    AH_Outline  outline = hinter->glyph;
    FT_Int      dimension;
    FT_Int      n_edges;


    edges      = outline->horz_edges;
    edge_limit = edges + outline->num_hedges;

    for ( dimension = 1; dimension >= 0; dimension-- )
    {
      AH_Edge  edge;
      AH_Edge  anchor = 0;
      int      has_serifs = 0;


      if ( !hinter->do_horz_hints && !dimension )
        goto Next_Dimension;

      if ( !hinter->do_vert_hints && dimension )
        goto Next_Dimension;

      /* we begin by aligning all stems relative to the blue zone */
      /* if needed -- that's only for horizontal edges            */
      if ( dimension )
      {
        for ( edge = edges; edge < edge_limit; edge++ )
        {
          FT_Pos*      blue;
          AH_EdgeRec  *edge1, *edge2;


          if ( edge->flags & AH_EDGE_DONE )
            continue;

          blue  = edge->blue_edge;
          edge1 = 0;
          edge2 = edge->link;

          if ( blue )
          {
            edge1 = edge;
          }
          else if ( edge2 && edge2->blue_edge )
          {
            blue  = edge2->blue_edge;
            edge1 = edge2;
            edge2 = edge;
          }

          if ( !edge1 )
            continue;