path: root/gs/src/gxhint1.c

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*/

/*$Id$ */
/* 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;
}