harvey/sys/src/cmd/gs/src/gxhint1.c

/* Copyright (C) 1990, 1992, 1993, 1997, 1998 Aladdin Enterprises.  All rights reserved.
  
  This file is part of AFPL Ghostscript.
  
  AFPL Ghostscript is distributed with NO WARRANTY OF ANY KIND.  No author or
  distributor accepts any responsibility for the consequences of using it, or
  for whether it serves any particular purpose or works at all, unless he or
  she says so in writing.  Refer to the Aladdin Free Public License (the
  "License") for full details.
  
  Every copy of AFPL Ghostscript must include a copy of the License, normally
  in a plain ASCII text file named PUBLIC.  The License grants you the right
  to copy, modify and redistribute AFPL Ghostscript, but only under certain
  conditions described in the License.  Among other things, the License
  requires that the copyright notice and this notice be preserved on all
  copies.
*/

/*$Id: gxhint1.c,v 1.2 2000/09/19 19:00:37 lpd Exp $ */
/* Font level hints for Type 1 fonts */
#include "gx.h"
#include "gserrors.h"
#include "gxarith.h"
#include "gxfixed.h"
#include "gxmatrix.h"
#include "gxfont.h"
#include "gxfont1.h"
#include "gxtype1.h"

/* Define whether to use font hints. */
/* Only set this to false for debugging the hint machinery. */
static bool USE_HINTS = true;

/* ------ Initialization ------ */

typedef zone_table(1) a_zone_table;
typedef stem_table(1) a_stem_table;
private void
    compute_snaps(P6(const gs_matrix_fixed *, const a_stem_table *,
		     stem_snap_table *, int, int, const char *));
private alignment_zone *
    compute_zones(P6(const gs_matrix_fixed *, const font_hints *,
	const a_zone_table *, const a_zone_table *, alignment_zone *, int));
private int
    transform_zone(P4(const gs_matrix_fixed *, const font_hints *,
		      const float *, alignment_zone *));

/* Reset the font-level hints. */
void
reset_font_hints(font_hints * pfh, const gs_log2_scale_point * plog2_scale)
{
    set_pixel_scale(&pfh->scale.x, plog2_scale->x);
    set_pixel_scale(&pfh->scale.y, plog2_scale->y);
    pfh->axes_swapped = pfh->x_inverted = pfh->y_inverted = false;
    pfh->use_x_hints = pfh->use_y_hints = false;
    pfh->snap_h.count = pfh->snap_v.count = 0;
    pfh->a_zone_count = 0;
}

/* Compute the font-level hints from the font and the matrix. */
/* We should cache this with the font/matrix pair.... */
void
compute_font_hints(font_hints * pfh, const gs_matrix_fixed * pmat,
       const gs_log2_scale_point * plog2_scale, const gs_type1_data * pdata)
{
    alignment_zone *zp = &pfh->a_zones[0];

    reset_font_hints(pfh, plog2_scale);
    /* Figure out which hints, if any, to use, */
    /* and the orientation of the axes. */
    if (is_fzero(pmat->xy))
	pfh->y_inverted = is_fneg(pmat->yy),
	    pfh->use_y_hints = USE_HINTS;
    else if (is_fzero(pmat->xx))
	pfh->y_inverted = is_fneg(pmat->xy),
	    pfh->axes_swapped = true,
	    pfh->use_y_hints = USE_HINTS;
    if (is_fzero(pmat->yx))
	pfh->x_inverted = is_fneg(pmat->xx),
	    pfh->use_x_hints = USE_HINTS;
    else if (is_fzero(pmat->yy))
	pfh->x_inverted = is_fneg(pmat->yx),
	    pfh->axes_swapped = true,
	    pfh->use_x_hints = USE_HINTS;
    if_debug6('y', "[y]ctm=[%g %g %g %g %g %g]\n",
	      pmat->xx, pmat->xy, pmat->yx, pmat->yy,
	      pmat->tx, pmat->ty);
    if_debug7('y', "[y]scale=%d/%d, swapped=%d, x/y_hints=%d,%d, x/y_inverted=%d,%d\n",
	      1 << plog2_scale->x, 1 << plog2_scale->y,
	      pfh->axes_swapped, pfh->use_x_hints, pfh->use_y_hints,
	      pfh->x_inverted, pfh->y_inverted);
    /* Transform the actual hints. */
    if (pfh->use_x_hints) {
	compute_snaps(pmat, (const a_stem_table *)&pdata->StdHW,
		      &pfh->snap_h, 0, pfh->axes_swapped, "h");
	compute_snaps(pmat, (const a_stem_table *)&pdata->StemSnapH,
		      &pfh->snap_h, 0, pfh->axes_swapped, "h");
    }
    if (pfh->use_y_hints) {
	gs_fixed_point vw;
	fixed *vp = (pfh->axes_swapped ? &vw.x : &vw.y);
	pixel_scale *psp =
	(pfh->axes_swapped ? &pfh->scale.x : &pfh->scale.y);

	/* Convert BlueFuzz to device pixels. */
	if (gs_distance_transform2fixed(pmat, 0.0,
					(float)pdata->BlueFuzz,
					&vw) < 0
	    )
	    vw.x = vw.y = fixed_0;
	pfh->blue_fuzz = any_abs(*vp);
	/*
	 * Decide whether to suppress overshoots.  The formula in
	 * section 5.6 of the "Adobe Type 1 Font Format" says that
	 * at 300 dpi, if BlueScale = (P - 0.49) / 240, overshoot
	 * suppression turns off at point sizes at least P, i.e.:
	 *      P >= BlueScale * 240 + 0.49.
	 * At 300 dpi, P = |CTM.yy| / (300/72), so the condition is
	 * equivalent to
	 *      |CTM.yy| >= BlueScale * 1000 + 2.0417,
	 * or
	 *      BlueScale >= (|CTM.yy| - 2.0417) / 1000.
	 * Since *pmat is the concatenation of the FontMatrix and
	 * CTM, if we assume a 1000-unit scale, this is equivalent to
	 *      BlueScale >= |pmat->yy| - 0.00020417.
	 * Since the constant term is slightly smaller than
	 * fixed_epsilon, we just disregard it.
	 *
	 * According to the same section of the Adobe documentation,
	 * there is a requirement that BlueScale times the maximum
	 * alignment zone height must be less than 1.  We enforced
	 * this when the font was constructed (in zfont1.c).
	 */
	if (gs_distance_transform2fixed(pmat, 0.0, 1.0, &vw) < 0)
	    vw.x = vw.y = fixed_0;
	pfh->suppress_overshoot =
	    fixed2float(any_abs(*vp) >> psp->log2_unit) <
	    pdata->BlueScale;
	if (gs_distance_transform2fixed(pmat, 0.0, pdata->BlueShift,
					&vw) < 0
	    )
	    vw.x = vw.y = fixed_0;
	pfh->blue_shift = any_abs(*vp);
	/*
	 * Don't let the blue shift exceed half a pixel.
	 * See the discussion of BlueShift in section 5.7 of the
	 * "Adobe Type 1 Font Format" book.
	 */
	if (pfh->blue_shift > psp->half)
	    pfh->blue_shift = psp->half;
	if_debug6('y', "[y]blue_fuzz=%d->%g, blue_scale=%g, blue_shift=%g->%g, sup_ov=%d\n",
		  pdata->BlueFuzz, fixed2float(pfh->blue_fuzz),
		  pdata->BlueScale,
		  pdata->BlueShift, fixed2float(pfh->blue_shift),
		  pfh->suppress_overshoot);
	zp = compute_zones(pmat, pfh,
			   (const a_zone_table *)&pdata->BlueValues,
			   (const a_zone_table *)&pdata->FamilyBlues,
			   zp, 1);
	zp = compute_zones(pmat, pfh,
			   (const a_zone_table *)&pdata->OtherBlues,
			   (const a_zone_table *)&pdata->FamilyOtherBlues,
			   zp, max_OtherBlues);
	compute_snaps(pmat, (const a_stem_table *)&pdata->StdVW,
		      &pfh->snap_v, 1, !pfh->axes_swapped, "v");
	compute_snaps(pmat, (const a_stem_table *)&pdata->StemSnapV,
		      &pfh->snap_v, 1, !pfh->axes_swapped, "v");
    }
    pfh->a_zone_count = zp - &pfh->a_zones[0];
}

/* Transform one set of stem snap widths. */
private void
compute_snaps(const gs_matrix_fixed * pmat, const a_stem_table * pst,
	    stem_snap_table * psst, int from_y, int to_y, const char *tname)
{
    gs_fixed_point wxy;
    fixed *wp = (to_y ? &wxy.y : &wxy.x);
    int i;
    int j = psst->count;

    for (i = 0; i < pst->count; i++) {
	float w = pst->values[i];
	int code =
	(from_y ?
	 gs_distance_transform2fixed(pmat, 0.0, w, &wxy) :
	 gs_distance_transform2fixed(pmat, w, 0.0, &wxy)
	);

	if (code < 0)
	    continue;
	psst->data[j] = any_abs(*wp);
	if_debug3('y', "[y]snap_%s[%d]=%g\n", tname, j,
		  fixed2float(psst->data[j]));
	j++;
    }
    psst->count = j;
}

/* Compute the alignment zones for one set of 'blue' values. */
private alignment_zone *
compute_zones(const gs_matrix_fixed * pmat, const font_hints * pfh,
	      const a_zone_table * blues, const a_zone_table * family_blues,
	      alignment_zone * zp, int bottom_count)
{
    int i;
    fixed fuzz = pfh->blue_fuzz;
    int inverted =
    (pfh->axes_swapped ? pfh->x_inverted : pfh->y_inverted);

    for (i = 0; i < blues->count; i += 2) {
	const float *vp = &blues->values[i];

	zp->is_top_zone = i >> 1 >= bottom_count;
	if (transform_zone(pmat, pfh, vp, zp) < 0)
	    continue;
	if_debug5('y', "[y]blues[%d]=%g,%g -> %g,%g\n",
		  i >> 1, vp[0], vp[1],
		  fixed2float(zp->v0), fixed2float(zp->v1));
	if (i < family_blues->count) {	/* Check whether family blues should supersede. */
	    alignment_zone fz;
	    const float *fvp = &family_blues->values[i];
	    fixed unit = (pfh->axes_swapped ?
			  pfh->scale.x.unit : pfh->scale.y.unit);
	    fixed diff;

	    if (transform_zone(pmat, pfh, fvp, &fz) < 0)
		continue;
	    if_debug5('y', "[y]f_blues[%d]=%g,%g -> %g,%g\n",
		      i >> 1, fvp[0], fvp[1],
		      fixed2float(fz.v0), fixed2float(fz.v1));
	    diff = (zp->v1 - zp->v0) - (fz.v1 - fz.v0);
	    if (diff > -unit && diff < unit)
		zp->v0 = fz.v0, zp->v1 = fz.v1;
	}
	/* Compute the flat position, and add the fuzz. */
	if ((inverted ? zp->is_top_zone : !zp->is_top_zone))
	    zp->flat = zp->v1, zp->v0 -= fuzz;
	else
	    zp->flat = zp->v0, zp->v1 += fuzz;
	zp++;
    }
    return zp;
}

/* Transform a single alignment zone to device coordinates, */
/* taking axis swapping into account. */
private int
transform_zone(const gs_matrix_fixed * pmat, const font_hints * pfh,
	       const float *vp, alignment_zone * zp)
{
    gs_fixed_point p0, p1;
    fixed v0, v1;
    int code;

    if ((code = gs_point_transform2fixed(pmat, 0.0, vp[0], &p0)) < 0 ||
	(code = gs_point_transform2fixed(pmat, 0.0, vp[1], &p1)) < 0
	)
	return code;
    if (pfh->axes_swapped)
	v0 = p0.x, v1 = p1.x;
    else
	v0 = p0.y, v1 = p1.y;
    if (v0 <= v1)
	zp->v0 = v0, zp->v1 = v1;
    else
	zp->v0 = v1, zp->v1 = v0;
    return 0;
}