ref: 3c983eb84ab42c1d63304031b4704067810201d9
dir: /src/autofit/afwarp.c/
/****************************************************************************
*
* afwarp.c
*
* Auto-fitter warping algorithm (body).
*
* Copyright (C) 2006-2020 by
* David Turner, Robert Wilhelm, and Werner Lemberg.
*
* This file is part of the FreeType project, and may only be used,
* modified, and distributed under the terms of the FreeType project
* license, LICENSE.TXT. By continuing to use, modify, or distribute
* this file you indicate that you have read the license and
* understand and accept it fully.
*
*/
/*
* The idea of the warping code is to slightly scale and shift a glyph
* within a single dimension so that as much of its segments are aligned
* (more or less) on the grid. To find out the optimal scaling and
* shifting value, various parameter combinations are tried and scored.
*/
#include "afwarp.h"
#ifdef AF_CONFIG_OPTION_USE_WARPER
/**************************************************************************
*
* The macro FT_COMPONENT is used in trace mode. It is an implicit
* parameter of the FT_TRACE() and FT_ERROR() macros, used to print/log
* messages during execution.
*/
#undef FT_COMPONENT
#define FT_COMPONENT afwarp
/* The weights cover the range 0/64 - 63/64 of a pixel. Obviously, */
/* values around a half pixel (which means exactly between two grid */
/* lines) gets the worst weight. */
#if 1
static const AF_WarpScore
af_warper_weights[64] =
{
35, 32, 30, 25, 20, 15, 12, 10, 5, 1, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, -1, -2, -5, -8,-10,-10,-20,-20,-30,-30,
-30,-30,-20,-20,-10,-10, -8, -5, -2, -1, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 1, 5, 10, 12, 15, 20, 25, 30, 32,
};
#else
static const AF_WarpScore
af_warper_weights[64] =
{
30, 20, 10, 5, 4, 4, 3, 2, 1, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, -1, -2, -2, -5, -5,-10,-10,-15,-20,
-20,-15,-15,-10,-10, -5, -5, -2, -2, -1, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 4, 5, 10, 20,
};
#endif
/* Score segments for a given `scale' and `delta' in the range */
/* `xx1' to `xx2', and store the best result in `warper'. If */
/* the new best score is equal to the old one, prefer the */
/* value with a smaller distortion (around `base_distort'). */
static void
af_warper_compute_line_best( AF_Warper warper,
FT_Fixed scale,
FT_Pos delta,
FT_Pos xx1,
FT_Pos xx2,
AF_WarpScore base_distort,
AF_Segment segments,
FT_Int num_segments )
{
FT_Int idx_min, idx_max, idx0;
FT_Int nn;
AF_WarpScore scores[65];
for ( nn = 0; nn < 65; nn++ )
scores[nn] = 0;
idx0 = xx1 - warper->t1;
/* compute minimum and maximum indices */
{
FT_Pos xx1min = warper->x1min;
FT_Pos xx1max = warper->x1max;
FT_Pos w = xx2 - xx1;
if ( xx1min + w < warper->x2min )
xx1min = warper->x2min - w;
if ( xx1max + w > warper->x2max )
xx1max = warper->x2max - w;
idx_min = xx1min - warper->t1;
idx_max = xx1max - warper->t1;
if ( idx_min < 0 || idx_min > idx_max || idx_max > 64 )
{
FT_TRACE5(( "invalid indices:\n" ));
FT_TRACE5(( " min=%d max=%d, xx1=%ld xx2=%ld,\n",
idx_min, idx_max, xx1, xx2 ));
FT_TRACE5(( " x1min=%ld x1max=%ld, x2min=%ld x2max=%ld\n",
warper->x1min, warper->x1max,
warper->x2min, warper->x2max ));
return;
}
}
for ( nn = 0; nn < num_segments; nn++ )
{
FT_Pos len = segments[nn].max_coord - segments[nn].min_coord;
FT_Pos y0 = FT_MulFix( segments[nn].pos, scale ) + delta;
FT_Pos y = y0 + ( idx_min - idx0 );
FT_Int idx;
/* score the length of the segments for the given range */
for ( idx = idx_min; idx <= idx_max; idx++, y++ )
scores[idx] += af_warper_weights[y & 63] * len;
}
/* find best score */
{
FT_Int idx;
for ( idx = idx_min; idx <= idx_max; idx++ )
{
AF_WarpScore score = scores[idx];
AF_WarpScore distort = base_distort + ( idx - idx0 );
if ( score > warper->best_score ||
( score == warper->best_score &&
distort < warper->best_distort ) )
{
warper->best_score = score;
warper->best_distort = distort;
warper->best_scale = scale;
warper->best_delta = delta + ( idx - idx0 );
}
}
}
}
/* Compute optimal scaling and delta values for a given glyph and */
/* dimension. */
FT_LOCAL_DEF( void )
af_warper_compute( AF_Warper warper,
AF_GlyphHints hints,
AF_Dimension dim,
FT_Fixed *a_scale,
FT_Pos *a_delta )
{
AF_AxisHints axis;
AF_Point points;
FT_Fixed org_scale;
FT_Pos org_delta;
FT_Int nn, num_points, num_segments;
FT_Int X1, X2;
FT_Int w;
AF_WarpScore base_distort;
AF_Segment segments;
/* get original scaling transformation */
if ( dim == AF_DIMENSION_VERT )
{
org_scale = hints->y_scale;
org_delta = hints->y_delta;
}
else
{
org_scale = hints->x_scale;
org_delta = hints->x_delta;
}
warper->best_scale = org_scale;
warper->best_delta = org_delta;
warper->best_score = FT_INT_MIN;
warper->best_distort = 0;
axis = &hints->axis[dim];
segments = axis->segments;
num_segments = axis->num_segments;
points = hints->points;
num_points = hints->num_points;
*a_scale = org_scale;
*a_delta = org_delta;
/* get X1 and X2, minimum and maximum in original coordinates */
if ( num_segments < 1 )
return;
#if 1
X1 = X2 = points[0].fx;
for ( nn = 1; nn < num_points; nn++ )
{
FT_Int X = points[nn].fx;
if ( X < X1 )
X1 = X;
if ( X > X2 )
X2 = X;
}
#else
X1 = X2 = segments[0].pos;
for ( nn = 1; nn < num_segments; nn++ )
{
FT_Int X = segments[nn].pos;
if ( X < X1 )
X1 = X;
if ( X > X2 )
X2 = X;
}
#endif
if ( X1 >= X2 )
return;
warper->x1 = FT_MulFix( X1, org_scale ) + org_delta;
warper->x2 = FT_MulFix( X2, org_scale ) + org_delta;
warper->t1 = AF_WARPER_FLOOR( warper->x1 );
warper->t2 = AF_WARPER_CEIL( warper->x2 );
/* examine a half pixel wide range around the maximum coordinates */
warper->x1min = warper->x1 & ~31;
warper->x1max = warper->x1min + 32;
warper->x2min = warper->x2 & ~31;
warper->x2max = warper->x2min + 32;
if ( warper->x1max > warper->x2 )
warper->x1max = warper->x2;
if ( warper->x2min < warper->x1 )
warper->x2min = warper->x1;
warper->w0 = warper->x2 - warper->x1;
if ( warper->w0 <= 64 )
{
warper->x1max = warper->x1;
warper->x2min = warper->x2;
}
/* examine (at most) a pixel wide range around the natural width */
warper->wmin = warper->x2min - warper->x1max;
warper->wmax = warper->x2max - warper->x1min;
#if 1
/* some heuristics to reduce the number of widths to be examined */
{
int margin = 16;
if ( warper->w0 <= 128 )
{
margin = 8;
if ( warper->w0 <= 96 )
margin = 4;
}
if ( warper->wmin < warper->w0 - margin )
warper->wmin = warper->w0 - margin;
if ( warper->wmax > warper->w0 + margin )
warper->wmax = warper->w0 + margin;
}
if ( warper->wmin < warper->w0 * 3 / 4 )
warper->wmin = warper->w0 * 3 / 4;
if ( warper->wmax > warper->w0 * 5 / 4 )
warper->wmax = warper->w0 * 5 / 4;
#else
/* no scaling, just translation */
warper->wmin = warper->wmax = warper->w0;
#endif
for ( w = warper->wmin; w <= warper->wmax; w++ )
{
FT_Fixed new_scale;
FT_Pos new_delta;
FT_Pos xx1, xx2;
/* compute min and max positions for given width, */
/* assuring that they stay within the coordinate ranges */
xx1 = warper->x1;
xx2 = warper->x2;
if ( w >= warper->w0 )
{
xx1 -= w - warper->w0;
if ( xx1 < warper->x1min )
{
xx2 += warper->x1min - xx1;
xx1 = warper->x1min;
}
}
else
{
xx1 -= w - warper->w0;
if ( xx1 > warper->x1max )
{
xx2 -= xx1 - warper->x1max;
xx1 = warper->x1max;
}
}
if ( xx1 < warper->x1 )
base_distort = warper->x1 - xx1;
else
base_distort = xx1 - warper->x1;
if ( xx2 < warper->x2 )
base_distort += warper->x2 - xx2;
else
base_distort += xx2 - warper->x2;
/* give base distortion a greater weight while scoring */
base_distort *= 10;
new_scale = org_scale + FT_DivFix( w - warper->w0, X2 - X1 );
new_delta = xx1 - FT_MulFix( X1, new_scale );
af_warper_compute_line_best( warper, new_scale, new_delta, xx1, xx2,
base_distort,
segments, num_segments );
}
{
FT_Fixed best_scale = warper->best_scale;
FT_Pos best_delta = warper->best_delta;
hints->xmin_delta = FT_MulFix( X1, best_scale - org_scale )
+ best_delta;
hints->xmax_delta = FT_MulFix( X2, best_scale - org_scale )
+ best_delta;
*a_scale = best_scale;
*a_delta = best_delta;
}
}
#else /* !AF_CONFIG_OPTION_USE_WARPER */
/* ANSI C doesn't like empty source files */
typedef int _af_warp_dummy;
#endif /* !AF_CONFIG_OPTION_USE_WARPER */
/* END */