freetype2/src/cff/cf2font.c

/***************************************************************************/
/*                                                                         */
/*  cf2font.c                                                              */
/*                                                                         */
/*    Adobe's code for font instances (body).                              */
/*                                                                         */
/*  Copyright 2007-2013 Adobe Systems Incorporated.                        */
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/***************************************************************************/


#include "cf2ft.h"

#include "cf2glue.h"
#include "cf2font.h"
#include "cf2error.h"
#include "cf2intrp.h"


  /* Compute a stem darkening amount in character space. */
  static void
  cf2_computeDarkening( CF2_Fixed   emRatio,
                        CF2_Fixed   ppem,
                        CF2_Fixed   stemWidth,
                        CF2_Fixed*  darkenAmount,
                        CF2_Fixed   boldenAmount,
                        FT_Bool     stemDarkened,
                        FT_Int*     darkenParams )
  {
    /*
     * Total darkening amount is computed in 1000 unit character space
     * using the modified 5 part curve as Adobe's Avalon rasterizer.
     * The darkening amount is smaller for thicker stems.
     * It becomes zero when the stem is thicker than 2.333 pixels.
     *
     * By default, we use
     *
     *   darkenAmount = 0.4 pixels   if scaledStem <= 0.5 pixels,
     *   darkenAmount = 0.275 pixels if 1 <= scaledStem <= 1.667 pixels,
     *   darkenAmount = 0 pixel      if scaledStem >= 2.333 pixels,
     *
     * and piecewise linear in-between:
     *
     *
     *   darkening
     *       ^
     *       |
     *       |      (x1,y1)
     *       |--------+
     *       |         \
     *       |          \
     *       |           \          (x3,y3)
     *       |            +----------+
     *       |        (x2,y2)         \
     *       |                         \
     *       |                          \
     *       |                           +-----------------
     *       |                         (x4,y4)
     *       +--------------------------------------------->   stem
     *                                                       thickness
     *
     *
     * This corresponds to the following values for the
     * `darkening-parameters' property:
     *
     *   (x1, y1) = (500, 400)
     *   (x2, y2) = (1000, 275)
     *   (x3, y3) = (1667, 275)
     *   (x4, y4) = (2333, 0)
     *
     */

    /* Internal calculations are done in units per thousand for */
    /* convenience.                                             */
    CF2_Fixed  stemWidthPer1000, scaledStem;


    if ( boldenAmount == 0 && !stemDarkened )
      return;

    /* protect against range problems and divide by zero */
    if ( emRatio < cf2_floatToFixed( .01 ) )
      return;

    if ( stemDarkened )
    {
      FT_Int  x1 = darkenParams[0];
      FT_Int  y1 = darkenParams[1];
      FT_Int  x2 = darkenParams[2];
      FT_Int  y2 = darkenParams[3];
      FT_Int  x3 = darkenParams[4];
      FT_Int  y3 = darkenParams[5];
      FT_Int  x4 = darkenParams[6];
      FT_Int  y4 = darkenParams[7];


      /* convert from true character space to 1000 unit character space; */
      /* add synthetic emboldening effect                                */

      /* we have to assure that the computation of `scaledStem' */
      /* and `stemWidthPer1000' don't overflow                  */

      stemWidthPer1000 = FT_MulFix( stemWidth + boldenAmount, emRatio );

      if ( emRatio > CF2_FIXED_ONE                          &&
           stemWidthPer1000 <= ( stemWidth + boldenAmount ) )
      {
        stemWidthPer1000 = 0;                      /* to pacify compiler */
        scaledStem       = cf2_intToFixed( x4 );
      }
      else
      {
        scaledStem = FT_MulFix( stemWidthPer1000, ppem );

        if ( ppem > CF2_FIXED_ONE           &&
             scaledStem <= stemWidthPer1000 )
          scaledStem = cf2_intToFixed( x4 );
      }

      /* now apply the darkening parameters */

      if ( scaledStem < cf2_intToFixed( x1 ) )
        *darkenAmount = FT_DivFix( cf2_intToFixed( y1 ), ppem );

      else if ( scaledStem < cf2_intToFixed( x2 ) )
      {
        FT_Int  xdelta = x2 - x1;
        FT_Int  ydelta = y2 - y1;
        FT_Int  x      = stemWidthPer1000 -
                           FT_DivFix( cf2_intToFixed( x1 ), ppem );


        if ( !ydelta )
          goto Try_x3;

        *darkenAmount = FT_MulFix( x, FT_DivFix( ydelta, xdelta ) ) +
                          FT_DivFix( cf2_intToFixed( y1 ), ppem );
      }

      else if ( scaledStem < cf2_intToFixed( x3 ) )
      {
      Try_x3:
        {
          FT_Int  xdelta = x3 - x2;
          FT_Int  ydelta = y3 - y2;
          FT_Int  x      = stemWidthPer1000 -
                             FT_DivFix( cf2_intToFixed( x2 ), ppem );


          if ( !ydelta )
            goto Try_x4;

          *darkenAmount = FT_MulFix( x, FT_DivFix( ydelta, xdelta ) ) +
                            FT_DivFix( cf2_intToFixed( y2 ), ppem );
        }
      }

      else if ( scaledStem < cf2_intToFixed( x4 ) )
      {
      Try_x4:
        {
          FT_Int  xdelta = x4 - x3;
          FT_Int  ydelta = y4 - y3;
          FT_Int  x      = stemWidthPer1000 -
                             FT_DivFix( cf2_intToFixed( x3 ), ppem );


          if ( !ydelta )
            goto Use_y4;

          *darkenAmount = FT_MulFix( x, FT_DivFix( ydelta, xdelta ) ) +
                            FT_DivFix( cf2_intToFixed( y3 ), ppem );
        }
      }

      else
      {
      Use_y4:
        *darkenAmount = FT_DivFix( cf2_intToFixed( y4 ), ppem );
      }

      /* use half the amount on each side and convert back to true */
      /* character space                                           */
      *darkenAmount = FT_DivFix( *darkenAmount, 2 * emRatio );
    }

    /* add synthetic emboldening effect in character space */
    *darkenAmount += boldenAmount / 2;
  }


  /* set up values for the current FontDict and matrix */

  /* caller's transform is adjusted for subpixel positioning */
  static void
  cf2_font_setup( CF2_Font           font,
                  const CF2_Matrix*  transform )
  {
    /* pointer to parsed font object */
    CFF_Decoder*  decoder = font->decoder;

    FT_Bool  needExtraSetup;

    /* character space units */
    CF2_Fixed  boldenX = font->syntheticEmboldeningAmountX;
    CF2_Fixed  boldenY = font->syntheticEmboldeningAmountY;

    CF2_Fixed  ppem;


    /* clear previous error */
    font->error = FT_Err_Ok;

    /* if a CID fontDict has changed, we need to recompute some cached */
    /* data                                                            */
    needExtraSetup =
      (FT_Bool)( font->lastSubfont != cf2_getSubfont( decoder ) );

    /* if ppem has changed, we need to recompute some cached data         */
    /* note: because of CID font matrix concatenation, ppem and transform */
    /*       do not necessarily track.                                    */
    ppem = cf2_getPpemY( decoder );
    if ( font->ppem != ppem )
    {
      font->ppem     = ppem;
      needExtraSetup = TRUE;
    }

    /* copy hinted flag on each call */
    font->hinted = (FT_Bool)( font->renderingFlags & CF2_FlagsHinted );

    /* determine if transform has changed;       */
    /* include Fontmatrix but ignore translation */
    if ( ft_memcmp( transform,
                    &font->currentTransform,
                    4 * sizeof ( CF2_Fixed ) ) != 0 )
    {
      /* save `key' information for `cache of one' matrix data; */
      /* save client transform, without the translation         */
      font->currentTransform    = *transform;
      font->currentTransform.tx =
      font->currentTransform.ty = cf2_intToFixed( 0 );

      /* TODO: FreeType transform is simple scalar; for now, use identity */
      /*       for outer                                                  */
      font->innerTransform   = *transform;
      font->outerTransform.a =
      font->outerTransform.d = cf2_intToFixed( 1 );
      font->outerTransform.b =
      font->outerTransform.c = cf2_intToFixed( 0 );

      needExtraSetup = TRUE;
    }

    /*
     * font->darkened is set to true if there is a stem darkening request or
     * the font is synthetic emboldened.
     * font->darkened controls whether to adjust blue zones, winding order,
     * and hinting.
     *
     */
    if ( font->stemDarkened != ( font->renderingFlags & CF2_FlagsDarkened ) )
    {
      font->stemDarkened =
        (FT_Bool)( font->renderingFlags & CF2_FlagsDarkened );

      /* blue zones depend on darkened flag */
      needExtraSetup = TRUE;
    }

    /* recompute variables that are dependent on transform or FontDict or */
    /* darken flag                                                        */
    if ( needExtraSetup )
    {
      /* StdVW is found in the private dictionary;                       */
      /* recompute darkening amounts whenever private dictionary or      */
      /* transform change                                                */
      /* Note: a rendering flag turns darkening on or off, so we want to */
      /*       store the `on' amounts;                                   */
      /*       darkening amount is computed in character space           */
      /* TODO: testing size-dependent darkening here;                    */
      /*       what to do for rotations?                                 */

      CF2_Fixed  emRatio;
      CF2_Fixed  stdHW;
      CF2_Int    unitsPerEm = font->unitsPerEm;


      if ( unitsPerEm == 0 )
        unitsPerEm = 1000;

      ppem = FT_MAX( cf2_intToFixed( 4 ),
                     font->ppem ); /* use minimum ppem of 4 */

#if 0
      /* since vstem is measured in the x-direction, we use the `a' member */
      /* of the fontMatrix                                                 */
      emRatio = cf2_fixedFracMul( cf2_intToFixed( 1000 ), fontMatrix->a );
#endif

      /* Freetype does not preserve the fontMatrix when parsing; use */
      /* unitsPerEm instead.                                         */
      /* TODO: check precision of this                               */
      emRatio     = cf2_intToFixed( 1000 ) / unitsPerEm;
      font->stdVW = cf2_getStdVW( decoder );

      if ( font->stdVW <= 0 )
        font->stdVW = FT_DivFix( cf2_intToFixed( 75 ), emRatio );

      if ( boldenX > 0 )
      {
        /* Ensure that boldenX is at least 1 pixel for synthetic bold font */
        /* (similar to what Avalon does)                                   */
        boldenX = FT_MAX( boldenX,
                          FT_DivFix( cf2_intToFixed( unitsPerEm ), ppem ) );

        /* Synthetic emboldening adds at least 1 pixel to darkenX, while */
        /* stem darkening adds at most half pixel.  Since the purpose of */
        /* stem darkening (readability at small sizes) is met with       */
        /* synthetic emboldening, no need to add stem darkening for a    */
        /* synthetic bold font.                                          */
        cf2_computeDarkening( emRatio,
                              ppem,
                              font->stdVW,
                              &font->darkenX,
                              boldenX,
                              FALSE,
                              font->darkenParams );
      }
      else
        cf2_computeDarkening( emRatio,
                              ppem,
                              font->stdVW,
                              &font->darkenX,
                              0,
                              font->stemDarkened,
                              font->darkenParams );

#if 0
      /* since hstem is measured in the y-direction, we use the `d' member */
      /* of the fontMatrix                                                 */
      /* TODO: use the same units per em as above; check this              */
      emRatio = cf2_fixedFracMul( cf2_intToFixed( 1000 ), fontMatrix->d );
#endif

      /* set the default stem width, because it must be the same for all */
      /* family members;                                                 */
      /* choose a constant for StdHW that depends on font contrast       */
      stdHW = cf2_getStdHW( decoder );

      if ( stdHW > 0 && font->stdVW > 2 * stdHW )
        font->stdHW = FT_DivFix( cf2_intToFixed( 75 ), emRatio );
      else
      {
        /* low contrast font gets less hstem darkening */
        font->stdHW = FT_DivFix( cf2_intToFixed( 110 ), emRatio );
      }

      cf2_computeDarkening( emRatio,
                            ppem,
                            font->stdHW,
                            &font->darkenY,
                            boldenY,
                            font->stemDarkened,
                            font->darkenParams );

      if ( font->darkenX != 0 || font->darkenY != 0 )
        font->darkened = TRUE;
      else
        font->darkened = FALSE;

      font->reverseWinding = FALSE; /* initial expectation is CCW */

      /* compute blue zones for this instance */
      cf2_blues_init( &font->blues, font );
    }
  }


  /* equivalent to AdobeGetOutline */
  FT_LOCAL_DEF( FT_Error )
  cf2_getGlyphOutline( CF2_Font           font,
                       CF2_Buffer         charstring,
                       const CF2_Matrix*  transform,
                       CF2_F16Dot16*      glyphWidth )
  {
    FT_Error  lastError = FT_Err_Ok;

    FT_Vector  translation;

#if 0
    FT_Vector  advancePoint;
#endif

    CF2_Fixed  advWidth = 0;
    FT_Bool    needWinding;


    /* Note: use both integer and fraction for outlines.  This allows bbox */
    /*       to come out directly.                                         */

    translation.x = transform->tx;
    translation.y = transform->ty;

    /* set up values based on transform */
    cf2_font_setup( font, transform );
    if ( font->error )
      goto exit;                      /* setup encountered an error */

    /* reset darken direction */
    font->reverseWinding = FALSE;

    /* winding order only affects darkening */
    needWinding = font->darkened;

    while ( 1 )
    {
      /* reset output buffer */
      cf2_outline_reset( &font->outline );

      /* build the outline, passing the full translation */
      cf2_interpT2CharString( font,
                              charstring,
                              (CF2_OutlineCallbacks)&font->outline,
                              &translation,
                              FALSE,
                              0,
                              0,
                              &advWidth );

      if ( font->error )
        goto exit;

      if ( !needWinding )
        break;

      /* check winding order */
      if ( font->outline.root.windingMomentum >= 0 ) /* CFF is CCW */
        break;

      /* invert darkening and render again                            */
      /* TODO: this should be a parameter to getOutline-computeOffset */
      font->reverseWinding = TRUE;

      needWinding = FALSE;    /* exit after next iteration */
    }

    /* finish storing client outline */
    cf2_outline_close( &font->outline );

  exit:
    /* FreeType just wants the advance width; there is no translation */
    *glyphWidth = advWidth;

    /* free resources and collect errors from objects we've used */
    cf2_setError( &font->error, lastError );

    return font->error;
  }


/* END */