ref: d1540c7f666e3c5d636b48c956b444205b50502d
dir: /libfreetype/ahoptim.c/
/***************************************************************************/
/* */
/* ahoptim.c */
/* */
/* FreeType auto hinting outline optimization (body). */
/* */
/* Copyright 2000-2001, 2002 Catharon Productions Inc. */
/* Author: David Turner */
/* */
/* This file is part of the Catharon Typography Project and shall only */
/* be used, modified, and distributed under the terms of the Catharon */
/* Open Source License that should come with this file under the name */
/* `CatharonLicense.txt'. By continuing to use, modify, or distribute */
/* this file you indicate that you have read the license and */
/* understand and accept it fully. */
/* */
/* Note that this license is compatible with the FreeType license. */
/* */
/***************************************************************************/
/*************************************************************************/
/* */
/* This module is in charge of optimising the outlines produced by the */
/* auto-hinter in direct mode. This is required at small pixel sizes in */
/* order to ensure coherent spacing, among other things.. */
/* */
/* The technique used in this module is a simplified simulated */
/* annealing. */
/* */
/*************************************************************************/
#include <ft2build.h>
#include FT_INTERNAL_OBJECTS_H /* for FT_ALLOC_ARRAY() and FT_FREE() */
#include "ahoptim.h"
/* define this macro to use brute force optimization -- this is slow, */
/* but a good way to perfect the distortion function `by hand' through */
/* tweaking */
#define AH_BRUTE_FORCE
#define xxxAH_DEBUG_OPTIM
#undef LOG
#ifdef AH_DEBUG_OPTIM
#define LOG( x ) optim_log ## x
#else
#define LOG( x )
#endif /* AH_DEBUG_OPTIM */
#ifdef AH_DEBUG_OPTIM
#include <stdarg.h>
#include <stdlib.h>
#define FLOAT( x ) ( (float)( (x) / 64.0 ) )
static void
optim_log( const char* fmt, ... )
{
va_list ap;
va_start( ap, fmt );
vprintf( fmt, ap );
va_end( ap );
}
static void
AH_Dump_Stems( AH_Optimizer* optimizer )
{
int n;
AH_Stem* stem;
stem = optimizer->stems;
for ( n = 0; n < optimizer->num_stems; n++, stem++ )
{
LOG(( " %c%2d [%.1f:%.1f]={%.1f:%.1f}="
"<%1.f..%1.f> force=%.1f speed=%.1f\n",
optimizer->vertical ? 'V' : 'H', n,
FLOAT( stem->edge1->opos ), FLOAT( stem->edge2->opos ),
FLOAT( stem->edge1->pos ), FLOAT( stem->edge2->pos ),
FLOAT( stem->min_pos ), FLOAT( stem->max_pos ),
FLOAT( stem->force ), FLOAT( stem->velocity ) ));
}
}
static void
AH_Dump_Stems2( AH_Optimizer* optimizer )
{
int n;
AH_Stem* stem;
stem = optimizer->stems;
for ( n = 0; n < optimizer->num_stems; n++, stem++ )
{
LOG(( " %c%2d [%.1f]=<%1.f..%1.f> force=%.1f speed=%.1f\n",
optimizer->vertical ? 'V' : 'H', n,
FLOAT( stem->pos ),
FLOAT( stem->min_pos ), FLOAT( stem->max_pos ),
FLOAT( stem->force ), FLOAT( stem->velocity ) ));
}
}
static void
AH_Dump_Springs( AH_Optimizer* optimizer )
{
int n;
AH_Spring* spring;
AH_Stem* stems;
spring = optimizer->springs;
stems = optimizer->stems;
LOG(( "%cSprings ", optimizer->vertical ? 'V' : 'H' ));
for ( n = 0; n < optimizer->num_springs; n++, spring++ )
{
LOG(( " [%d-%d:%.1f:%1.f:%.1f]",
spring->stem1 - stems, spring->stem2 - stems,
FLOAT( spring->owidth ),
FLOAT( spring->stem2->pos -
( spring->stem1->pos + spring->stem1->width ) ),
FLOAT( spring->tension ) ));
}
LOG(( "\n" ));
}
#endif /* AH_DEBUG_OPTIM */
/*************************************************************************/
/*************************************************************************/
/*************************************************************************/
/**** ****/
/**** COMPUTE STEMS AND SPRINGS IN AN OUTLINE ****/
/**** ****/
/*************************************************************************/
/*************************************************************************/
/*************************************************************************/
static int
valid_stem_segments( AH_Segment seg1,
AH_Segment seg2 )
{
return seg1->serif == 0 &&
seg2 &&
seg2->link == seg1 &&
seg1->pos < seg2->pos &&
seg1->min_coord <= seg2->max_coord &&
seg2->min_coord <= seg1->max_coord;
}
/* compute all stems in an outline */
static int
optim_compute_stems( AH_Optimizer* optimizer )
{
AH_Outline outline = optimizer->outline;
FT_Fixed scale;
FT_Memory memory = optimizer->memory;
FT_Error error = 0;
FT_Int dimension;
AH_Edge edges;
AH_Edge edge_limit;
AH_Stem** p_stems;
FT_Int* p_num_stems;
edges = outline->horz_edges;
edge_limit = edges + outline->num_hedges;
scale = outline->y_scale;
p_stems = &optimizer->horz_stems;
p_num_stems = &optimizer->num_hstems;
for ( dimension = 1; dimension >= 0; dimension-- )
{
AH_Stem* stems = 0;
FT_Int num_stems = 0;
AH_Edge edge;
/* first of all, count the number of stems in this direction */
for ( edge = edges; edge < edge_limit; edge++ )
{
AH_Segment seg = edge->first;
do
{
if (valid_stem_segments( seg, seg->link ) )
num_stems++;
seg = seg->edge_next;
} while ( seg != edge->first );
}
/* now allocate the stems and build their table */
if ( num_stems > 0 )
{
AH_Stem* stem;
if ( FT_NEW_ARRAY( stems, num_stems ) )
goto Exit;
stem = stems;
for ( edge = edges; edge < edge_limit; edge++ )
{
AH_Segment seg = edge->first;
AH_Segment seg2;
do
{
seg2 = seg->link;
if ( valid_stem_segments( seg, seg2 ) )
{
AH_Edge edge1 = seg->edge;
AH_Edge edge2 = seg2->edge;
stem->edge1 = edge1;
stem->edge2 = edge2;
stem->opos = edge1->opos;
stem->pos = edge1->pos;
stem->owidth = edge2->opos - edge1->opos;
stem->width = edge2->pos - edge1->pos;
/* compute min_coord and max_coord */
{
FT_Pos min_coord = seg->min_coord;
FT_Pos max_coord = seg->max_coord;
if ( seg2->min_coord > min_coord )
min_coord = seg2->min_coord;
if ( seg2->max_coord < max_coord )
max_coord = seg2->max_coord;
stem->min_coord = min_coord;
stem->max_coord = max_coord;
}
/* compute minimum and maximum positions for stem -- */
/* note that the left-most/bottom-most stem has always */
/* a fixed position */
if ( stem == stems || edge1->blue_edge || edge2->blue_edge )
{
/* this stem cannot move; it is snapped to a blue edge */
stem->min_pos = stem->pos;
stem->max_pos = stem->pos;
}
else
{
/* this edge can move; compute its min and max positions */
FT_Pos pos1 = stem->opos;
FT_Pos pos2 = pos1 + stem->owidth - stem->width;
FT_Pos min1 = pos1 & -64;
FT_Pos min2 = pos2 & -64;
stem->min_pos = min1;
stem->max_pos = min1 + 64;
if ( min2 < min1 )
stem->min_pos = min2;
else
stem->max_pos = min2 + 64;
/* XXX: just to see what it does */
stem->max_pos += 64;
/* just for the case where direct hinting did some */
/* incredible things (e.g. blue edge shifts) */
if ( stem->min_pos > stem->pos )
stem->min_pos = stem->pos;
if ( stem->max_pos < stem->pos )
stem->max_pos = stem->pos;
}
stem->velocity = 0;
stem->force = 0;
stem++;
}
seg = seg->edge_next;
} while ( seg != edge->first );
}
}
*p_stems = stems;
*p_num_stems = num_stems;
edges = outline->vert_edges;
edge_limit = edges + outline->num_vedges;
scale = outline->x_scale;
p_stems = &optimizer->vert_stems;
p_num_stems = &optimizer->num_vstems;
}
Exit:
#ifdef AH_DEBUG_OPTIM
AH_Dump_Stems( optimizer );
#endif
return error;
}
/* returns the spring area between two stems, 0 if none */
static FT_Pos
stem_spring_area( AH_Stem* stem1,
AH_Stem* stem2 )
{
FT_Pos area1 = stem1->max_coord - stem1->min_coord;
FT_Pos area2 = stem2->max_coord - stem2->min_coord;
FT_Pos min = stem1->min_coord;
FT_Pos max = stem1->max_coord;
FT_Pos area;
/* order stems */
if ( stem2->opos <= stem1->opos + stem1->owidth )
return 0;
if ( min < stem2->min_coord )
min = stem2->min_coord;
if ( max < stem2->max_coord )
max = stem2->max_coord;
area = ( max-min );
if ( 2 * area < area1 && 2 * area < area2 )
area = 0;
return area;
}
/* compute all springs in an outline */
static int
optim_compute_springs( AH_Optimizer* optimizer )
{
/* basically, a spring exists between two stems if most of their */
/* surface is aligned */
FT_Memory memory = optimizer->memory;
AH_Stem* stems;
AH_Stem* stem_limit;
AH_Stem* stem;
int dimension;
int error = 0;
FT_Int* p_num_springs;
AH_Spring** p_springs;
stems = optimizer->horz_stems;
stem_limit = stems + optimizer->num_hstems;
p_springs = &optimizer->horz_springs;
p_num_springs = &optimizer->num_hsprings;
for ( dimension = 1; dimension >= 0; dimension-- )
{
FT_Int num_springs = 0;
AH_Spring* springs = 0;
/* first of all, count stem springs */
for ( stem = stems; stem + 1 < stem_limit; stem++ )
{
AH_Stem* stem2;
for ( stem2 = stem+1; stem2 < stem_limit; stem2++ )
if ( stem_spring_area( stem, stem2 ) )
num_springs++;
}
/* then allocate and build the springs table */
if ( num_springs > 0 )
{
AH_Spring* spring;
/* allocate table of springs */
if ( FT_NEW_ARRAY( springs, num_springs ) )
goto Exit;
/* fill the springs table */
spring = springs;
for ( stem = stems; stem+1 < stem_limit; stem++ )
{
AH_Stem* stem2;
FT_Pos area;
for ( stem2 = stem + 1; stem2 < stem_limit; stem2++ )
{
area = stem_spring_area( stem, stem2 );
if ( area )
{
/* add a new spring here */
spring->stem1 = stem;
spring->stem2 = stem2;
spring->owidth = stem2->opos - ( stem->opos + stem->owidth );
spring->tension = 0;
spring++;
}
}
}
}
*p_num_springs = num_springs;
*p_springs = springs;
stems = optimizer->vert_stems;
stem_limit = stems + optimizer->num_vstems;
p_springs = &optimizer->vert_springs;
p_num_springs = &optimizer->num_vsprings;
}
Exit:
#ifdef AH_DEBUG_OPTIM
AH_Dump_Springs( optimizer );
#endif
return error;
}
/*************************************************************************/
/*************************************************************************/
/*************************************************************************/
/**** ****/
/**** OPTIMIZE THROUGH MY STRANGE SIMULATED ANNEALING ALGO ;-) ****/
/**** ****/
/*************************************************************************/
/*************************************************************************/
/*************************************************************************/
#ifndef AH_BRUTE_FORCE
/* compute all spring tensions */
static void
optim_compute_tensions( AH_Optimizer* optimizer )
{
AH_Spring* spring = optimizer->springs;
AH_Spring* limit = spring + optimizer->num_springs;
for ( ; spring < limit; spring++ )
{
AH_Stem* stem1 = spring->stem1;
AH_Stem* stem2 = spring->stem2;
FT_Int status;
FT_Pos width;
FT_Pos tension;
FT_Pos sign;
/* compute the tension; it simply is -K*(new_width-old_width) */
width = stem2->pos - ( stem1->pos + stem1->width );
tension = width - spring->owidth;
sign = 1;
if ( tension < 0 )
{
sign = -1;
tension = -tension;
}
if ( width <= 0 )
tension = 32000;
else
tension = ( tension << 10 ) / width;
tension = -sign * FT_MulFix( tension, optimizer->tension_scale );
spring->tension = tension;
/* now, distribute tension among the englobing stems, if they */
/* are able to move */
status = 0;
if ( stem1->pos <= stem1->min_pos )
status |= 1;
if ( stem2->pos >= stem2->max_pos )
status |= 2;
if ( !status )
tension /= 2;
if ( ( status & 1 ) == 0 )
stem1->force -= tension;
if ( ( status & 2 ) == 0 )
stem2->force += tension;
}
}
/* compute all stem movements -- returns 0 if nothing moved */
static int
optim_compute_stem_movements( AH_Optimizer* optimizer )
{
AH_Stem* stems = optimizer->stems;
AH_Stem* limit = stems + optimizer->num_stems;
AH_Stem* stem = stems;
int moved = 0;
/* set initial forces to velocity */
for ( stem = stems; stem < limit; stem++ )
{
stem->force = stem->velocity;
stem->velocity /= 2; /* XXX: Heuristics */
}
/* compute the sum of forces applied on each stem */
optim_compute_tensions( optimizer );
#ifdef AH_DEBUG_OPTIM
AH_Dump_Springs( optimizer );
AH_Dump_Stems2( optimizer );
#endif
/* now, see whether something can move */
for ( stem = stems; stem < limit; stem++ )
{
if ( stem->force > optimizer->tension_threshold )
{
/* there is enough tension to move the stem to the right */
if ( stem->pos < stem->max_pos )
{
stem->pos += 64;
stem->velocity = stem->force / 2;
moved = 1;
}
else
stem->velocity = 0;
}
else if ( stem->force < optimizer->tension_threshold )
{
/* there is enough tension to move the stem to the left */
if ( stem->pos > stem->min_pos )
{
stem->pos -= 64;
stem->velocity = stem->force / 2;
moved = 1;
}
else
stem->velocity = 0;
}
}
/* return 0 if nothing moved */
return moved;
}
#endif /* AH_BRUTE_FORCE */
/* compute current global distortion from springs */
static FT_Pos
optim_compute_distortion( AH_Optimizer* optimizer )
{
AH_Spring* spring = optimizer->springs;
AH_Spring* limit = spring + optimizer->num_springs;
FT_Pos distortion = 0;
for ( ; spring < limit; spring++ )
{
AH_Stem* stem1 = spring->stem1;
AH_Stem* stem2 = spring->stem2;
FT_Pos width;
width = stem2->pos - ( stem1->pos + stem1->width );
width -= spring->owidth;
if ( width < 0 )
width = -width;
distortion += width;
}
return distortion;
}
/* record stems configuration in `best of' history */
static void
optim_record_configuration( AH_Optimizer* optimizer )
{
FT_Pos distortion;
AH_Configuration* configs = optimizer->configs;
AH_Configuration* limit = configs + optimizer->num_configs;
AH_Configuration* config;
distortion = optim_compute_distortion( optimizer );
LOG(( "config distortion = %.1f ", FLOAT( distortion * 64 ) ));
/* check that we really need to add this configuration to our */
/* sorted history */
if ( limit > configs && limit[-1].distortion < distortion )
{
LOG(( "ejected\n" ));
return;
}
/* add new configuration at the end of the table */
{
int n;
config = limit;
if ( optimizer->num_configs < AH_MAX_CONFIGS )
optimizer->num_configs++;
else
config--;
config->distortion = distortion;
for ( n = 0; n < optimizer->num_stems; n++ )
config->positions[n] = optimizer->stems[n].pos;
}
/* move the current configuration towards the front of the list */
/* when necessary -- yes this is slow bubble sort ;-) */
while ( config > configs && config[0].distortion < config[-1].distortion )
{
AH_Configuration temp;
config--;
temp = config[0];
config[0] = config[1];
config[1] = temp;
}
LOG(( "recorded!\n" ));
}
#ifdef AH_BRUTE_FORCE
/* optimize outline in a single direction */
static void
optim_compute( AH_Optimizer* optimizer )
{
int n;
FT_Bool moved;
AH_Stem* stem = optimizer->stems;
AH_Stem* limit = stem + optimizer->num_stems;
/* empty, exit */
if ( stem >= limit )
return;
optimizer->num_configs = 0;
stem = optimizer->stems;
for ( ; stem < limit; stem++ )
stem->pos = stem->min_pos;
do
{
/* record current configuration */
optim_record_configuration( optimizer );
/* now change configuration */
moved = 0;
for ( stem = optimizer->stems; stem < limit; stem++ )
{
if ( stem->pos < stem->max_pos )
{
stem->pos += 64;
moved = 1;
break;
}
stem->pos = stem->min_pos;
}
} while ( moved );
/* now, set the best stem positions */
for ( n = 0; n < optimizer->num_stems; n++ )
{
AH_Stem* stem = optimizer->stems + n;
FT_Pos pos = optimizer->configs[0].positions[n];
stem->edge1->pos = pos;
stem->edge2->pos = pos + stem->width;
stem->edge1->flags |= AH_EDGE_DONE;
stem->edge2->flags |= AH_EDGE_DONE;
}
}
#else /* AH_BRUTE_FORCE */
/* optimize outline in a single direction */
static void
optim_compute( AH_Optimizer* optimizer )
{
int n, counter, counter2;
optimizer->num_configs = 0;
optimizer->tension_scale = 0x80000L;
optimizer->tension_threshold = 64;
/* record initial configuration threshold */
optim_record_configuration( optimizer );
counter = 0;
for ( counter2 = optimizer->num_stems*8; counter2 >= 0; counter2-- )
{
if ( counter == 0 )
counter = 2 * optimizer->num_stems;
if ( !optim_compute_stem_movements( optimizer ) )
break;
optim_record_configuration( optimizer );
counter--;
if ( counter == 0 )
optimizer->tension_scale /= 2;
}
/* now, set the best stem positions */
for ( n = 0; n < optimizer->num_stems; n++ )
{
AH_Stem* stem = optimizer->stems + n;
FT_Pos pos = optimizer->configs[0].positions[n];
stem->edge1->pos = pos;
stem->edge2->pos = pos + stem->width;
stem->edge1->flags |= AH_EDGE_DONE;
stem->edge2->flags |= AH_EDGE_DONE;
}
}
#endif /* AH_BRUTE_FORCE */
/*************************************************************************/
/*************************************************************************/
/*************************************************************************/
/**** ****/
/**** HIGH-LEVEL OPTIMIZER API ****/
/**** ****/
/*************************************************************************/
/*************************************************************************/
/*************************************************************************/
/* releases the optimization data */
void
AH_Optimizer_Done( AH_Optimizer* optimizer )
{
if ( optimizer )
{
FT_Memory memory = optimizer->memory;
FT_FREE( optimizer->horz_stems );
FT_FREE( optimizer->vert_stems );
FT_FREE( optimizer->horz_springs );
FT_FREE( optimizer->vert_springs );
FT_FREE( optimizer->positions );
}
}
/* loads the outline into the optimizer */
int
AH_Optimizer_Init( AH_Optimizer* optimizer,
AH_Outline outline,
FT_Memory memory )
{
FT_Error error;
FT_MEM_ZERO( optimizer, sizeof ( *optimizer ) );
optimizer->outline = outline;
optimizer->memory = memory;
LOG(( "initializing new optimizer\n" ));
/* compute stems and springs */
error = optim_compute_stems ( optimizer ) ||
optim_compute_springs( optimizer );
if ( error )
goto Fail;
/* allocate stem positions history and configurations */
{
int n, max_stems;
max_stems = optimizer->num_hstems;
if ( max_stems < optimizer->num_vstems )
max_stems = optimizer->num_vstems;
if ( FT_NEW_ARRAY( optimizer->positions, max_stems * AH_MAX_CONFIGS ) )
goto Fail;
optimizer->num_configs = 0;
for ( n = 0; n < AH_MAX_CONFIGS; n++ )
optimizer->configs[n].positions = optimizer->positions +
n * max_stems;
}
return error;
Fail:
AH_Optimizer_Done( optimizer );
return error;
}
/* compute optimal outline */
void
AH_Optimizer_Compute( AH_Optimizer* optimizer )
{
optimizer->num_stems = optimizer->num_hstems;
optimizer->stems = optimizer->horz_stems;
optimizer->num_springs = optimizer->num_hsprings;
optimizer->springs = optimizer->horz_springs;
if ( optimizer->num_springs > 0 )
{
LOG(( "horizontal optimization ------------------------\n" ));
optim_compute( optimizer );
}
optimizer->num_stems = optimizer->num_vstems;
optimizer->stems = optimizer->vert_stems;
optimizer->num_springs = optimizer->num_vsprings;
optimizer->springs = optimizer->vert_springs;
if ( optimizer->num_springs )
{
LOG(( "vertical optimization --------------------------\n" ));
optim_compute( optimizer );
}
}
/* END */