ftstroke.c

下载来的一个看图软件的源代码

    /* copy tags */
    {
      FT_UInt   count = border->num_points;
      FT_Byte*  read  = border->tags;
      FT_Byte*  write = (FT_Byte*)outline->tags + outline->n_points;


      for ( ; count > 0; count--, read++, write++ )
      {
        if ( *read & FT_STROKE_TAG_ON )
          *write = FT_CURVE_TAG_ON;
        else if ( *read & FT_STROKE_TAG_CUBIC )
          *write = FT_CURVE_TAG_CUBIC;
        else
          *write = FT_CURVE_TAG_CONIC;
      }
    }

    /* copy contours */
    {
      FT_UInt    count = border->num_points;
      FT_Byte*   tags  = border->tags;
      FT_Short*  write = outline->contours + outline->n_contours;
      FT_Short   idx   = (FT_Short)outline->n_points;


      for ( ; count > 0; count--, tags++, idx++ )
      {
        if ( *tags & FT_STROKE_TAG_END )
        {
          *write++ = idx;
          outline->n_contours++;
        }
      }
    }

    outline->n_points  = (short)( outline->n_points + border->num_points );

    FT_ASSERT( FT_Outline_Check( outline ) == 0 );
  }


 /***************************************************************************/
 /***************************************************************************/
 /*****                                                                 *****/
 /*****                           STROKER                               *****/
 /*****                                                                 *****/
 /***************************************************************************/
 /***************************************************************************/

#define FT_SIDE_TO_ROTATE( s )   ( FT_ANGLE_PI2 - (s) * FT_ANGLE_PI )

  typedef struct  FT_StrokerRec_
  {
    FT_Angle             angle_in;
    FT_Angle             angle_out;
    FT_Vector            center;
    FT_Bool              first_point;
    FT_Bool              subpath_open;
    FT_Angle             subpath_angle;
    FT_Vector            subpath_start;

    FT_Stroker_LineCap   line_cap;
    FT_Stroker_LineJoin  line_join;
    FT_Fixed             miter_limit;
    FT_Fixed             radius;

    FT_Bool              valid;
    FT_StrokeBorderRec   borders[2];
    FT_Memory            memory;

  } FT_StrokerRec;


  FT_EXPORT_DEF( FT_Error )
  FT_Stroker_New( FT_Memory    memory,
                  FT_Stroker  *astroker )
  {
    FT_Error    error;
    FT_Stroker  stroker;


    if ( !FT_NEW( stroker ) )
    {
      stroker->memory = memory;

      ft_stroke_border_init( &stroker->borders[0], memory );
      ft_stroke_border_init( &stroker->borders[1], memory );
    }
    *astroker = stroker;
    return error;
  }


  FT_EXPORT_DEF( void )
  FT_Stroker_Set( FT_Stroker           stroker,
                  FT_Fixed             radius,
                  FT_Stroker_LineCap   line_cap,
                  FT_Stroker_LineJoin  line_join,
                  FT_Fixed             miter_limit )
  {
    stroker->radius      = radius;
    stroker->line_cap    = line_cap;
    stroker->line_join   = line_join;
    stroker->miter_limit = miter_limit;

    stroker->valid = 0;

    ft_stroke_border_reset( &stroker->borders[0] );
    ft_stroke_border_reset( &stroker->borders[1] );
  }


  FT_EXPORT_DEF( void )
  FT_Stroker_Done( FT_Stroker  stroker )
  {
    if ( stroker )
    {
      FT_Memory  memory = stroker->memory;


      ft_stroke_border_done( &stroker->borders[0] );
      ft_stroke_border_done( &stroker->borders[1] );

      stroker->memory = NULL;
      FT_FREE( stroker );
    }
  }


  /* creates a circular arc at a corner or cap */
  static FT_Error
  ft_stroker_arcto( FT_Stroker  stroker,
                    FT_Int      side )
  {
    FT_Angle         total, rotate;
    FT_Fixed         radius = stroker->radius;
    FT_Error         error  = 0;
    FT_StrokeBorder  border = stroker->borders + side;


    rotate = FT_SIDE_TO_ROTATE( side );

    total = FT_Angle_Diff( stroker->angle_in, stroker->angle_out );
    if ( total == FT_ANGLE_PI )
      total = -rotate * 2;

    error = ft_stroke_border_arcto( border,
                                    &stroker->center,
                                    radius,
                                    stroker->angle_in + rotate,
                                    total );
    border->movable = 0;
    return error;
  }


  /* adds a cap at the end of an opened path */
  static FT_Error
  ft_stroker_cap( FT_Stroker  stroker,
                  FT_Angle    angle,
                  FT_Int      side )
  {
    FT_Error  error  = 0;


    if ( stroker->line_cap == FT_STROKER_LINECAP_ROUND )
    {
      /* add a round cap */
      stroker->angle_in  = angle;
      stroker->angle_out = angle + FT_ANGLE_PI;
      error = ft_stroker_arcto( stroker, side );
    }
    else if ( stroker->line_cap == FT_STROKER_LINECAP_SQUARE )
    {
      /* add a square cap */
      FT_Vector        delta, delta2;
      FT_Angle         rotate = FT_SIDE_TO_ROTATE( side );
      FT_Fixed         radius = stroker->radius;
      FT_StrokeBorder  border = stroker->borders + side;


      FT_Vector_From_Polar( &delta2, radius, angle + rotate );
      FT_Vector_From_Polar( &delta,  radius, angle );

      delta.x += stroker->center.x + delta2.x;
      delta.y += stroker->center.y + delta2.y;

      error = ft_stroke_border_lineto( border, &delta, 0 );
      if ( error )
        goto Exit;

      FT_Vector_From_Polar( &delta2, radius, angle - rotate );
      FT_Vector_From_Polar( &delta,  radius, angle );

      delta.x += delta2.x + stroker->center.x;
      delta.y += delta2.y + stroker->center.y;

      error = ft_stroke_border_lineto( border, &delta, 0 );
    }

  Exit:
    return error;
  }


  /* process an inside corner, i.e. compute intersection */
  static FT_Error
  ft_stroker_inside( FT_Stroker  stroker,
                     FT_Int      side)
  {
    FT_StrokeBorder  border = stroker->borders + side;
    FT_Angle         phi, theta, rotate;
    FT_Fixed         length, thcos, sigma;
    FT_Vector        delta;
    FT_Error         error = 0;


    rotate = FT_SIDE_TO_ROTATE( side );

    /* compute median angle */
    theta = FT_Angle_Diff( stroker->angle_in, stroker->angle_out );
    if ( theta == FT_ANGLE_PI )
      theta = rotate;
    else
      theta = theta / 2;

    phi = stroker->angle_in + theta;

    thcos  = FT_Cos( theta );
    sigma  = FT_MulFix( stroker->miter_limit, thcos );

    if ( sigma < 0x10000L )
    {
      FT_Vector_From_Polar( &delta, stroker->radius,
                            stroker->angle_out + rotate );
      delta.x += stroker->center.x;
      delta.y += stroker->center.y;
      border->movable = 0;
    }
    else
    {
      length = FT_DivFix( stroker->radius, thcos );

      FT_Vector_From_Polar( &delta, length, phi + rotate );
      delta.x += stroker->center.x;
      delta.y += stroker->center.y;
    }

    error = ft_stroke_border_lineto( border, &delta, 0 );

    return error;
  }


  /* process an outside corner, i.e. compute bevel/miter/round */
  static FT_Error
  ft_stroker_outside( FT_Stroker  stroker,
                      FT_Int      side )
  {
    FT_StrokeBorder  border = stroker->borders + side;
    FT_Error         error;
    FT_Angle         rotate;


    if ( stroker->line_join == FT_STROKER_LINEJOIN_ROUND )
    {
      error = ft_stroker_arcto( stroker, side );
    }
    else
    {
      /* this is a mitered or beveled corner */
      FT_Fixed  sigma, radius = stroker->radius;
      FT_Angle  theta, phi;
      FT_Fixed  thcos;
      FT_Bool   miter;


      rotate = FT_SIDE_TO_ROTATE( side );
      miter  = FT_BOOL( stroker->line_join == FT_STROKER_LINEJOIN_MITER );

      theta  = FT_Angle_Diff( stroker->angle_in, stroker->angle_out );
      if ( theta == FT_ANGLE_PI )
      {
        theta = rotate;
        phi   = stroker->angle_in;
      }
      else
      {
        theta = theta / 2;
        phi   = stroker->angle_in + theta + rotate;
      }

      thcos = FT_Cos( theta );
      sigma = FT_MulFix( stroker->miter_limit, thcos );

      if ( sigma >= 0x10000L )
        miter = 0;

      if ( miter )  /* this is a miter (broken angle) */
      {
        FT_Vector  middle, delta;
        FT_Fixed   length;


        /* compute middle point */
        FT_Vector_From_Polar( &middle,
                              FT_MulFix( radius, stroker->miter_limit ),
                              phi );
        middle.x += stroker->center.x;
        middle.y += stroker->center.y;

        /* compute first angle point */
        length = FT_MulFix( radius,
                            FT_DivFix( 0x10000L - sigma,
                                       ft_pos_abs( FT_Sin( theta ) ) ) );

        FT_Vector_From_Polar( &delta, length, phi + rotate );
        delta.x += middle.x;
        delta.y += middle.y;

        error = ft_stroke_border_lineto( border, &delta, 0 );
        if ( error )
          goto Exit;

        /* compute second angle point */
        FT_Vector_From_Polar( &delta, length, phi - rotate );
        delta.x += middle.x;
        delta.y += middle.y;

        error = ft_stroke_border_lineto( border, &delta, 0 );
        if ( error )
          goto Exit;

        /* finally, add a movable end point */
        FT_Vector_From_Polar( &delta, radius, stroker->angle_out + rotate );
        delta.x += stroker->center.x;
        delta.y += stroker->center.y;

        error = ft_stroke_border_lineto( border, &delta, 1 );
      }

      else /* this is a bevel (intersection) */
      {
        FT_Fixed   length;
        FT_Vector  delta;


        length = FT_DivFix( stroker->radius, thcos );

        FT_Vector_From_Polar( &delta, length, phi );
        delta.x += stroker->center.x;
        delta.y += stroker->center.y;

        error = ft_stroke_border_lineto( border, &delta, 0 );
        if (error) goto Exit;

        /* now add end point */
        FT_Vector_From_Polar( &delta, stroker->radius,
                              stroker->angle_out + rotate );
        delta.x += stroker->center.x;
        delta.y += stroker->center.y;

        error = ft_stroke_border_lineto( border, &delta, 1 );
      }
    }

  Exit:
    return error;
  }


  static FT_Error
  ft_stroker_process_corner( FT_Stroker  stroker )
  {
    FT_Error  error = 0;
    FT_Angle  turn;
    FT_Int    inside_side;


    turn = FT_Angle_Diff( stroker->angle_in, stroker->angle_out );

    /* no specific corner processing is required if the turn is 0 */
    if ( turn == 0 )
      goto Exit;

    /* when we turn to the right, the inside side is 0 */
    inside_side = 0;

    /* otherwise, the inside side is 1 */
    if ( turn < 0 )
      inside_side = 1;

    /* process the inside side */
    error = ft_stroker_inside( stroker, inside_side );
    if ( error )
      goto Exit;

    /* process the outside side */
    error = ft_stroker_outside( stroker, 1 - inside_side );

  Exit:
    return error;
  }


  /* add two points to the left and right borders corresponding to the */
  /* start of the subpath..                                            */
  static FT_Error
  ft_stroker_subpath_start( FT_Stroker  stroker,
                            FT_Angle    start_angle )
  {
    FT_Vector        delta;
    FT_Vector        point;
    FT_Error         error;
    FT_StrokeBorder  border;


    FT_Vector_From_Polar( &delta, stroker->radius,
                          start_angle + FT_ANGLE_PI2 );

    point.x = stroker->center.x + delta.x;
    point.y = stroker->center.y + delta.y;

    border = stroker->borders;
    error = ft_stroke_border_moveto( border, &point );
    if ( error )
      goto Exit;

    point.x = stroker->center.x - delta.x;
    point.y = stroker->center.y - delta.y;

    border++;
    error = ft_stroke_border_moveto( border, &point );

    /* save angle for last cap */
    stroker->subpath_angle = start_angle;
    stroker->first_point   = 0;

  Exit:
    return error;
  }


  FT_EXPORT_DEF( FT_Error )
  FT_Stroker_LineTo( FT_Stroker  stroker,
                     FT_Vector*  to )
  {
    FT_Error         error = 0;
    FT_StrokeBorder  border;
    FT_Vector        delta;
    FT_Angle         angle;
    FT_Int           side;

    delta.x = to->x - stroker->center.x;
    delta.y = to->y - stroker->center.y;

    angle = FT_Atan2( delta.x, delta.y );
    FT_Vector_From_Polar( &delta, stroker->radius, angle + FT_ANGLE_PI2 );

    /* process corner if necessary */
    if ( stroker->first_point )
    {
      /* This is the first segment of a subpath.  We need to     */
      /* add a point to each border at their respective starting */
      /* point locations.                                        */
      error = ft_stroker_subpath_start( stroker, angle );
      if ( error )
        goto Exit;
    }
    else
    {
      /* process the current corner */
      stroker->angle_out = angle;
      error = ft_stroker_process_corner( stroker );
      if ( error )
        goto Exit;
    }

    /* now add a line segment to both the "inside" and "outside" paths */

    for ( border = stroker->borders, side = 1; side >= 0; side--, border++ )
    {
      FT_Vector  point;


      point.x = to->x + delta.x;
      point.y = to->y + delta.y;

      error = ft_stroke_border_lineto( border, &point, 1 );
      if ( error )
        goto Exit;

      delta.x = -delta.x;
      delta.y = -delta.y;
    }

    stroker->angle_in = angle;
    stroker->center   = *to;

  Exit:
    return error;
  }


  FT_EXPORT_DEF( FT_Error )
  FT_Stroker_ConicTo( FT_Stroker  stroker,
                      FT_Vector*  control,
                      FT_Vector*  to )
  {
    FT_Error    error = 0;
    FT_Vector   bez_stack[34];
    FT_Vector*  arc;
    FT_Vector*  limit = bez_stack + 30;
    FT_Angle    start_angle;
    FT_Bool     first_arc = 1;


    arc    = bez_stack;
    arc[0] = *to;
    arc[1] = *control;
    arc[2] = stroker->center;

    while ( arc >= bez_stack )
    {
      FT_Angle  angle_in, angle_out;


      angle_in = angle_out = 0;  /* remove compiler warnings */

      if ( arc < limit                                             &&
           !ft_conic_is_small_enough( arc, &angle_in, &angle_out ) )
      {
        ft_conic_split( arc );
        arc += 2;
        continue;
      }

      if ( first_arc )
      {
        first_arc = 0;

        start_angle = angle_in;

        /* process corner if necessary */
        if ( stroker->first_point )
          error = ft_stroker_subpath_start( stroker, start_angle );
        else
        {
          stroker->angle_out = start_angle;
          error = ft_stroker_process_corner( stroker );
        }
      }

      /* the arc's angle is small enough; we can add it directly to each */