ftstroke.c

下载来的一个看图软件的源代码

      /* border                                                          */
      {
        FT_Vector  ctrl, end;
        FT_Angle   theta, phi, rotate;
        FT_Fixed   length;
        FT_Int     side;


        theta  = FT_Angle_Diff( angle_in, angle_out ) / 2;
        phi    = angle_in + theta;
        length = FT_DivFix( stroker->radius, FT_Cos( theta ) );

        for ( side = 0; side <= 1; side++ )
        {
          rotate = FT_SIDE_TO_ROTATE( side );

          /* compute control point */
          FT_Vector_From_Polar( &ctrl, length, phi + rotate );
          ctrl.x += arc[1].x;
          ctrl.y += arc[1].y;

          /* compute end point */
          FT_Vector_From_Polar( &end, stroker->radius, angle_out + rotate );
          end.x += arc[0].x;
          end.y += arc[0].y;

          error = ft_stroke_border_conicto( stroker->borders + side,
                                            &ctrl, &end );
          if ( error )
            goto Exit;
        }
      }

      arc -= 2;

      if ( arc < bez_stack )
        stroker->angle_in = angle_out;
    }

    stroker->center = *to;

  Exit:
    return error;
  }


  FT_EXPORT_DEF( FT_Error )
  FT_Stroker_CubicTo( FT_Stroker  stroker,
                      FT_Vector*  control1,
                      FT_Vector*  control2,
                      FT_Vector*  to )
  {
    FT_Error    error = 0;
    FT_Vector   bez_stack[37];
    FT_Vector*  arc;
    FT_Vector*  limit = bez_stack + 32;
    FT_Angle    start_angle;
    FT_Bool     first_arc = 1;


    arc    = bez_stack;
    arc[0] = *to;
    arc[1] = *control2;
    arc[2] = *control1;
    arc[3] = stroker->center;

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


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

      if ( arc < limit                                         &&
           !ft_cubic_is_small_enough( arc, &angle_in,
                                      &angle_mid, &angle_out ) )
      {
        ft_cubic_split( arc );
        arc += 3;
        continue;
      }

      if ( first_arc )
      {
        first_arc = 0;

        /* process corner if necessary */
        start_angle = angle_in;

        if ( stroker->first_point )
          error = ft_stroker_subpath_start( stroker, start_angle );
        else
        {
          stroker->angle_out = start_angle;
          error = ft_stroker_process_corner( stroker );
        }
        if ( error )
          goto Exit;
      }

      /* the arc's angle is small enough; we can add it directly to each */
      /* border                                                          */
      {
        FT_Vector  ctrl1, ctrl2, end;
        FT_Angle   theta1, phi1, theta2, phi2, rotate;
        FT_Fixed   length1, length2;
        FT_Int     side;


        theta1  = ft_pos_abs( angle_mid - angle_in ) / 2;
        theta2  = ft_pos_abs( angle_out - angle_mid ) / 2;
        phi1    = (angle_mid + angle_in ) / 2;
        phi2    = (angle_mid + angle_out ) / 2;
        length1 = FT_DivFix( stroker->radius, FT_Cos( theta1 ) );
        length2 = FT_DivFix( stroker->radius, FT_Cos(theta2) );

        for ( side = 0; side <= 1; side++ )
        {
          rotate = FT_SIDE_TO_ROTATE( side );

          /* compute control points */
          FT_Vector_From_Polar( &ctrl1, length1, phi1 + rotate );
          ctrl1.x += arc[2].x;
          ctrl1.y += arc[2].y;

          FT_Vector_From_Polar( &ctrl2, length2, phi2 + rotate );
          ctrl2.x += arc[1].x;
          ctrl2.y += arc[1].y;

          /* compute end point */
          FT_Vector_From_Polar( &end, stroker->radius, angle_out + rotate );
          end.x += arc[0].x;
          end.y += arc[0].y;

          error = ft_stroke_border_cubicto( stroker->borders + side,
                                            &ctrl1, &ctrl2, &end );
          if ( error )
            goto Exit;
        }
      }

      arc -= 3;
      if ( arc < bez_stack )
        stroker->angle_in = angle_out;
    }

    stroker->center = *to;

  Exit:
    return error;
  }


  FT_EXPORT_DEF( FT_Error )
  FT_Stroker_BeginSubPath( FT_Stroker  stroker,
                           FT_Vector*  to,
                           FT_Bool     open )
  {
    /* We cannot process the first point, because there is not enough      */
    /* information regarding its corner/cap.  The latter will be processed */
    /* in the "end_subpath" routine.                                       */
    /*                                                                     */
    stroker->first_point   = 1;
    stroker->center        = *to;
    stroker->subpath_open  = open;

    /* record the subpath start point index for each border */
    stroker->subpath_start = *to;
    return 0;
  }


  static FT_Error
  ft_stroker_add_reverse_left( FT_Stroker  stroker,
                               FT_Bool     open )
  {
    FT_StrokeBorder  right  = stroker->borders + 0;
    FT_StrokeBorder  left   = stroker->borders + 1;
    FT_Int           new_points;
    FT_Error         error  = 0;


    FT_ASSERT( left->start >= 0 );

    new_points = left->num_points - left->start;
    if ( new_points > 0 )
    {
      error = ft_stroke_border_grow( right, (FT_UInt)new_points );
      if ( error )
        goto Exit;

      {
        FT_Vector*  dst_point = right->points + right->num_points;
        FT_Byte*    dst_tag   = right->tags   + right->num_points;
        FT_Vector*  src_point = left->points  + left->num_points - 1;
        FT_Byte*    src_tag   = left->tags    + left->num_points - 1;

        while ( src_point >= left->points + left->start )
        {
          *dst_point = *src_point;
          *dst_tag   = *src_tag;

          if ( open )
            dst_tag[0] &= ~( FT_STROKE_TAG_BEGIN | FT_STROKE_TAG_END );
          else
          {
            /* switch begin/end tags if necessary.. */
            if ( dst_tag[0] & ( FT_STROKE_TAG_BEGIN | FT_STROKE_TAG_END ) )
              dst_tag[0] ^= ( FT_STROKE_TAG_BEGIN | FT_STROKE_TAG_END );
          }

          src_point--;
          src_tag--;
          dst_point++;
          dst_tag++;
        }
      }

      left->num_points   = left->start;
      right->num_points += new_points;

      right->movable = 0;
      left->movable  = 0;
    }

  Exit:
    return error;
  }


  /* there's a lot of magic in this function! */
  FT_EXPORT_DEF( FT_Error )
  FT_Stroker_EndSubPath( FT_Stroker  stroker )
  {
    FT_Error  error  = 0;


    if ( stroker->subpath_open )
    {
      FT_StrokeBorder  right = stroker->borders;

      /* All right, this is an opened path, we need to add a cap between */
      /* right & left, add the reverse of left, then add a final cap     */
      /* between left & right.                                           */
      error = ft_stroker_cap( stroker, stroker->angle_in, 0 );
      if ( error )
        goto Exit;

      /* add reversed points from "left" to "right" */
      error = ft_stroker_add_reverse_left( stroker, 1 );
      if ( error )
        goto Exit;

      /* now add the final cap */
      stroker->center = stroker->subpath_start;
      error = ft_stroker_cap( stroker,
                              stroker->subpath_angle + FT_ANGLE_PI, 0 );
      if ( error )
        goto Exit;

      /* Now end the right subpath accordingly.  The left one is */
      /* rewind and doesn't need further processing.             */
      ft_stroke_border_close( right );
    }
    else
    {
      FT_Angle  turn;
      FT_Int    inside_side;


      /* process the corner */
      stroker->angle_out = stroker->subpath_angle;
      turn               = FT_Angle_Diff( stroker->angle_in,
                                          stroker->angle_out );

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

        /* IMPORTANT: WE DO NOT PROCESS THE INSIDE BORDER HERE! */
        /* 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 );
        if ( error )
          goto Exit;
      }

      /* we will first end our two subpaths */
      ft_stroke_border_close( stroker->borders + 0 );
      ft_stroke_border_close( stroker->borders + 1 );

      /* now, add the reversed left subpath to "right" */
      error = ft_stroker_add_reverse_left( stroker, 0 );
      if ( error )
        goto Exit;
    }

  Exit:
    return error;
  }


  FT_EXPORT_DEF( FT_Error )
  FT_Stroker_GetCounts( FT_Stroker  stroker,
                        FT_UInt    *anum_points,
                        FT_UInt    *anum_contours )
  {
    FT_UInt   count1, count2, num_points   = 0;
    FT_UInt   count3, count4, num_contours = 0;
    FT_Error  error;


    error = ft_stroke_border_get_counts( stroker->borders + 0,
                                         &count1, &count2 );
    if ( error )
      goto Exit;

    error = ft_stroke_border_get_counts( stroker->borders + 1,
                                         &count3, &count4 );
    if ( error )
      goto Exit;

    num_points   = count1 + count3;
    num_contours = count2 + count4;

    stroker->valid = 1;

  Exit:
    *anum_points   = num_points;
    *anum_contours = num_contours;
    return error;
  }


  FT_EXPORT_DEF( void )
  FT_Stroker_Export( FT_Stroker   stroker,
                     FT_Outline*  outline )
  {
    if ( stroker->valid )
    {
      ft_stroke_border_export( stroker->borders + 0, outline );
      ft_stroke_border_export( stroker->borders + 1, outline );
    }
  }


  /*
   *  The following is very similar to FT_Outline_Decompose, except
   *  that we do support opened paths, and do not scale the outline.
   */
  FT_EXPORT_DEF( FT_Error )
  FT_Stroker_ParseOutline( FT_Stroker   stroker,
                           FT_Outline*  outline,
                           FT_Bool      opened )
  {
    FT_Vector   v_last;
    FT_Vector   v_control;
    FT_Vector   v_start;

    FT_Vector*  point;
    FT_Vector*  limit;
    char*       tags;

    FT_Error    error;

    FT_Int   n;         /* index of contour in outline     */
    FT_UInt  first;     /* index of first point in contour */
    FT_Int   tag;       /* current point's state           */


    if ( !outline || !stroker )
      return FT_Err_Invalid_Argument;

    first = 0;

    for ( n = 0; n < outline->n_contours; n++ )
    {
      FT_Int  last;  /* index of last point in contour */


      last  = outline->contours[n];
      limit = outline->points + last;

      v_start = outline->points[first];
      v_last  = outline->points[last];

      v_control = v_start;

      point = outline->points + first;
      tags  = outline->tags  + first;
      tag   = FT_CURVE_TAG( tags[0] );

      /* A contour cannot start with a cubic control point! */
      if ( tag == FT_CURVE_TAG_CUBIC )
        goto Invalid_Outline;

      /* check first point to determine origin */
      if ( tag == FT_CURVE_TAG_CONIC )
      {
        /* First point is conic control.  Yes, this happens. */
        if ( FT_CURVE_TAG( outline->tags[last] ) == FT_CURVE_TAG_ON )
        {
          /* start at last point if it is on the curve */
          v_start = v_last;
          limit--;
        }
        else
        {
          /* if both first and last points are conic,         */
          /* start at their middle and record its position    */
          /* for closure                                      */
          v_start.x = ( v_start.x + v_last.x ) / 2;
          v_start.y = ( v_start.y + v_last.y ) / 2;

          v_last = v_start;
        }
        point--;
        tags--;
      }

      error = FT_Stroker_BeginSubPath( stroker, &v_start, opened );
      if ( error )
        goto Exit;

      while ( point < limit )
      {
        point++;
        tags++;

        tag = FT_CURVE_TAG( tags[0] );
        switch ( tag )
        {
        case FT_CURVE_TAG_ON:  /* emit a single line_to */
          {
            FT_Vector  vec;


            vec.x = point->x;
            vec.y = point->y;

            error = FT_Stroker_LineTo( stroker, &vec );
            if ( error )
              goto Exit;
            continue;
          }

        case FT_CURVE_TAG_CONIC:  /* consume conic arcs */
          v_control.x = point->x;
          v_control.y = point->y;

        Do_Conic:
          if ( point < limit )
          {
            FT_Vector  vec;
            FT_Vector  v_middle;


            point++;
            tags++;
            tag = FT_CURVE_TAG( tags[0] );

            vec = point[0];

            if ( tag == FT_CURVE_TAG_ON )
            {
              error = FT_Stroker_ConicTo( stroker, &v_control, &vec );
              if ( error )
                goto Exit;
              continue;
            }

            if ( tag != FT_CURVE_TAG_CONIC )
              goto Invalid_Outline;

            v_middle.x = ( v_control.x + vec.x ) / 2;
            v_middle.y = ( v_control.y + vec.y ) / 2;

            error = FT_Stroker_ConicTo( stroker, &v_control, &v_middle );
            if ( error )
              goto Exit;

            v_control = vec;
            goto Do_Conic;
          }

          error = FT_Stroker_ConicTo( stroker, &v_control, &v_start );
          goto Close;

        default:  /* FT_CURVE_TAG_CUBIC */
          {
            FT_Vector  vec1, vec2;


            if ( point + 1 > limit                             ||
                 FT_CURVE_TAG( tags[1] ) != FT_CURVE_TAG_CUBIC )
              goto Invalid_Outline;

            point += 2;
            tags  += 2;

            vec1 = point[-2];
            vec2 = point[-1];

            if ( point <= limit )
            {
              FT_Vector  vec;


              vec = point[0];

              error = FT_Stroker_CubicTo( stroker, &vec1, &vec2, &vec );
              if ( error )
                goto Exit;
              continue;
            }

            error = FT_Stroker_CubicTo( stroker, &vec1, &vec2, &v_start );
            goto Close;
          }
        }
      }

    Close:
      if ( error )
        goto Exit;

      error = FT_Stroker_EndSubPath( stroker );
      if ( error )
        goto Exit;

      first = last + 1;
    }

    return 0;

  Exit:
    return error;

  Invalid_Outline:
    return FT_Err_Invalid_Outline;
  }


/* END */