ref: 034e5dbf92ea3a7ea7c9322e47a3a50ff23f7b55
dir: /src/autofit/afloader.c/
/****************************************************************************
*
* afloader.c
*
* Auto-fitter glyph loading routines (body).
*
* Copyright (C) 2003-2022 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.
*
*/
#include "afglobal.h"
#include "afloader.h"
#include "afhints.h"
#include "aferrors.h"
#include "afmodule.h"
#include <freetype/internal/ftcalc.h>
/* Initialize glyph loader. */
FT_LOCAL_DEF( void )
af_loader_init( AF_Loader loader,
AF_GlyphHints hints )
{
FT_ZERO( loader );
loader->hints = hints;
}
/* Reset glyph loader and compute globals if necessary. */
FT_LOCAL_DEF( FT_Error )
af_loader_reset( AF_Loader loader,
AF_Module module,
FT_Face face )
{
FT_Error error = FT_Err_Ok;
loader->face = face;
loader->globals = (AF_FaceGlobals)face->autohint.data;
if ( !loader->globals )
{
error = af_face_globals_new( face, &loader->globals, module );
if ( !error )
{
face->autohint.data =
(FT_Pointer)loader->globals;
face->autohint.finalizer =
(FT_Generic_Finalizer)af_face_globals_free;
}
}
return error;
}
/* Finalize glyph loader. */
FT_LOCAL_DEF( void )
af_loader_done( AF_Loader loader )
{
loader->face = NULL;
loader->globals = NULL;
loader->hints = NULL;
}
#define af_intToFixed( i ) \
( (FT_Fixed)( (FT_UInt32)(i) << 16 ) )
#define af_fixedToInt( x ) \
( (FT_Short)( ( (FT_UInt32)(x) + 0x8000U ) >> 16 ) )
#define af_floatToFixed( f ) \
( (FT_Fixed)( (f) * 65536.0 + 0.5 ) )
static FT_Error
af_loader_embolden_glyph_in_slot( AF_Loader loader,
FT_Face face,
AF_StyleMetrics style_metrics )
{
FT_Error error = FT_Err_Ok;
FT_GlyphSlot slot = face->glyph;
AF_FaceGlobals globals = loader->globals;
AF_WritingSystemClass writing_system_class;
FT_Size_Metrics* size_metrics = &face->size->internal->autohint_metrics;
FT_Pos stdVW = 0;
FT_Pos stdHW = 0;
FT_Bool size_changed = size_metrics->x_ppem !=
globals->stem_darkening_for_ppem;
FT_Fixed em_size = af_intToFixed( face->units_per_EM );
FT_Matrix scale_down_matrix = { 0x10000L, 0, 0, 0x10000L };
/* Skip stem darkening for broken fonts. */
if ( !face->units_per_EM )
{
error = FT_ERR( Corrupted_Font_Header );
goto Exit;
}
/*
* We depend on the writing system (script analyzers) to supply
* standard widths for the script of the glyph we are looking at. If
* it can't deliver, stem darkening is disabled.
*/
writing_system_class =
af_writing_system_classes[style_metrics->style_class->writing_system];
if ( writing_system_class->style_metrics_getstdw )
writing_system_class->style_metrics_getstdw( style_metrics,
&stdHW,
&stdVW );
else
{
error = FT_ERR( Unimplemented_Feature );
goto Exit;
}
if ( size_changed ||
( stdVW > 0 && stdVW != globals->standard_vertical_width ) )
{
FT_Fixed darken_by_font_units_x, darken_x;
darken_by_font_units_x =
af_loader_compute_darkening( loader,
face,
stdVW ) ;
darken_x = FT_MulFix( darken_by_font_units_x,
size_metrics->x_scale );
globals->standard_vertical_width = stdVW;
globals->stem_darkening_for_ppem = size_metrics->x_ppem;
globals->darken_x = af_fixedToInt( darken_x );
}
if ( size_changed ||
( stdHW > 0 && stdHW != globals->standard_horizontal_width ) )
{
FT_Fixed darken_by_font_units_y, darken_y;
darken_by_font_units_y =
af_loader_compute_darkening( loader,
face,
stdHW ) ;
darken_y = FT_MulFix( darken_by_font_units_y,
size_metrics->y_scale );
globals->standard_horizontal_width = stdHW;
globals->stem_darkening_for_ppem = size_metrics->x_ppem;
globals->darken_y = af_fixedToInt( darken_y );
/*
* Scale outlines down on the Y-axis to keep them inside their blue
* zones. The stronger the emboldening, the stronger the downscaling
* (plus heuristical padding to prevent outlines still falling out
* their zones due to rounding).
*
* Reason: `FT_Outline_Embolden' works by shifting the rightmost
* points of stems farther to the right, and topmost points farther
* up. This positions points on the Y-axis outside their
* pre-computed blue zones and leads to distortion when applying the
* hints in the code further below. Code outside this emboldening
* block doesn't know we are presenting it with modified outlines the
* analyzer didn't see!
*
* An unfortunate side effect of downscaling is that the emboldening
* effect is slightly decreased. The loss becomes more pronounced
* versus the CFF driver at smaller sizes, e.g., at 9ppem and below.
*/
globals->scale_down_factor =
FT_DivFix( em_size - ( darken_by_font_units_y + af_intToFixed( 8 ) ),
em_size );
}
FT_Outline_EmboldenXY( &slot->outline,
globals->darken_x,
globals->darken_y );
scale_down_matrix.yy = globals->scale_down_factor;
FT_Outline_Transform( &slot->outline, &scale_down_matrix );
Exit:
return error;
}
/* Load the glyph at index into the current slot of a face and hint it. */
FT_LOCAL_DEF( FT_Error )
af_loader_load_glyph( AF_Loader loader,
AF_Module module,
FT_Face face,
FT_UInt glyph_index,
FT_Int32 load_flags )
{
FT_Error error;
FT_Size size = face->size;
FT_Size_Internal size_internal = size->internal;
FT_GlyphSlot slot = face->glyph;
FT_Slot_Internal slot_internal = slot->internal;
FT_GlyphLoader gloader = slot_internal->loader;
AF_GlyphHints hints = loader->hints;
AF_ScalerRec scaler;
AF_StyleMetrics style_metrics;
FT_UInt style_options = AF_STYLE_NONE_DFLT;
AF_StyleClass style_class;
AF_WritingSystemClass writing_system_class;
if ( !size )
return FT_THROW( Invalid_Size_Handle );
FT_ZERO( &scaler );
if ( !size_internal->autohint_metrics.x_scale ||
size_internal->autohint_mode != FT_LOAD_TARGET_MODE( load_flags ) )
{
/* switching between hinting modes usually means different scaling */
/* values; this later on enforces recomputation of everything */
/* related to the current size */
size_internal->autohint_mode = FT_LOAD_TARGET_MODE( load_flags );
size_internal->autohint_metrics = size->metrics;
#ifdef AF_CONFIG_OPTION_TT_SIZE_METRICS
{
FT_Size_Metrics* size_metrics = &size_internal->autohint_metrics;
/* set metrics to integer values and adjust scaling accordingly; */
/* this is the same setup as with TrueType fonts, cf. function */
/* `tt_size_reset' in file `ttobjs.c' */
size_metrics->ascender = FT_PIX_ROUND(
FT_MulFix( face->ascender,
size_metrics->y_scale ) );
size_metrics->descender = FT_PIX_ROUND(
FT_MulFix( face->descender,
size_metrics->y_scale ) );
size_metrics->height = FT_PIX_ROUND(
FT_MulFix( face->height,
size_metrics->y_scale ) );
size_metrics->x_scale = FT_DivFix( size_metrics->x_ppem << 6,
face->units_per_EM );
size_metrics->y_scale = FT_DivFix( size_metrics->y_ppem << 6,
face->units_per_EM );
size_metrics->max_advance = FT_PIX_ROUND(
FT_MulFix( face->max_advance_width,
size_metrics->x_scale ) );
}
#endif /* AF_CONFIG_OPTION_TT_SIZE_METRICS */
}
/*
* TODO: This code currently doesn't support fractional advance widths,
* i.e., placing hinted glyphs at anything other than integer
* x-positions. This is only relevant for the warper code, which
* scales and shifts glyphs to optimize blackness of stems (hinting on
* the x-axis by nature places things on pixel integers, hinting on the
* y-axis only, i.e., LIGHT mode, doesn't touch the x-axis). The delta
* values of the scaler would need to be adjusted.
*/
scaler.face = face;
scaler.x_scale = size_internal->autohint_metrics.x_scale;
scaler.x_delta = 0;
scaler.y_scale = size_internal->autohint_metrics.y_scale;
scaler.y_delta = 0;
scaler.render_mode = FT_LOAD_TARGET_MODE( load_flags );
scaler.flags = 0;
/* note that the fallback style can't be changed anymore */
/* after the first call of `af_loader_load_glyph' */
error = af_loader_reset( loader, module, face );
if ( error )
goto Exit;
/*
* Glyphs (really code points) are assigned to scripts. Script
* analysis is done lazily: For each glyph that passes through here,
* the corresponding script analyzer is called, but returns immediately
* if it has been run already.
*/
error = af_face_globals_get_metrics( loader->globals, glyph_index,
style_options, &style_metrics );
if ( error )
goto Exit;
style_class = style_metrics->style_class;
writing_system_class =
af_writing_system_classes[style_class->writing_system];
loader->metrics = style_metrics;
if ( writing_system_class->style_metrics_scale )
writing_system_class->style_metrics_scale( style_metrics, &scaler );
else
style_metrics->scaler = scaler;
if ( writing_system_class->style_hints_init )
{
error = writing_system_class->style_hints_init( hints,
style_metrics );
if ( error )
goto Exit;
}
/*
* Do the main work of `af_loader_load_glyph'. Note that we never have
* to deal with composite glyphs as those get loaded into
* FT_GLYPH_FORMAT_OUTLINE by the recursed `FT_Load_Glyph' function.
* In the rare cases where FT_LOAD_NO_RECURSE is set, it implies
* FT_LOAD_NO_SCALE and as such the auto-hinter is never called.
*/
load_flags |= FT_LOAD_NO_SCALE |
FT_LOAD_IGNORE_TRANSFORM |
FT_LOAD_LINEAR_DESIGN;
load_flags &= ~FT_LOAD_RENDER;
error = FT_Load_Glyph( face, glyph_index, load_flags );
if ( error )
goto Exit;
/*
* Apply stem darkening (emboldening) here before hints are applied to
* the outline. Glyphs are scaled down proportionally to the
* emboldening so that curve points don't fall outside their
* precomputed blue zones.
*
* Any emboldening done by the font driver (e.g., the CFF driver)
* doesn't reach here because the autohinter loads the unprocessed
* glyphs in font units for analysis (functions `af_*_metrics_init_*')
* and then above to prepare it for the rasterizers by itself,
* independently of the font driver. So emboldening must be done here,
* within the autohinter.
*
* All glyphs to be autohinted pass through here one by one. The
* standard widths can therefore change from one glyph to the next,
* depending on what script a glyph is assigned to (each script has its
* own set of standard widths and other metrics). The darkening amount
* must therefore be recomputed for each size and
* `standard_{vertical,horizontal}_width' change.
*
* Ignore errors and carry on without emboldening.
*
*/
/* stem darkening only works well in `light' mode */
if ( scaler.render_mode == FT_RENDER_MODE_LIGHT &&
( !face->internal->no_stem_darkening ||
( face->internal->no_stem_darkening < 0 &&
!module->no_stem_darkening ) ) )
af_loader_embolden_glyph_in_slot( loader, face, style_metrics );
loader->transformed = slot_internal->glyph_transformed;
if ( loader->transformed )
{
FT_Matrix inverse;
loader->trans_matrix = slot_internal->glyph_matrix;
loader->trans_delta = slot_internal->glyph_delta;
inverse = loader->trans_matrix;
if ( !FT_Matrix_Invert( &inverse ) )
FT_Vector_Transform( &loader->trans_delta, &inverse );
}
switch ( slot->format )
{
case FT_GLYPH_FORMAT_OUTLINE:
/* translate the loaded glyph when an internal transform is needed */
if ( loader->transformed )
FT_Outline_Translate( &slot->outline,
loader->trans_delta.x,
loader->trans_delta.y );
/* compute original horizontal phantom points */
/* (and ignore vertical ones) */
loader->pp1.x = hints->x_delta;
loader->pp1.y = hints->y_delta;
loader->pp2.x = FT_MulFix( slot->metrics.horiAdvance,
hints->x_scale ) + hints->x_delta;
loader->pp2.y = hints->y_delta;
/* be sure to check for spacing glyphs */
if ( slot->outline.n_points == 0 )
goto Hint_Metrics;
/* now load the slot image into the auto-outline */
/* and run the automatic hinting process */
if ( writing_system_class->style_hints_apply )
{
error = writing_system_class->style_hints_apply(
glyph_index,
hints,
&gloader->base.outline,
style_metrics );
if ( error )
goto Exit;
}
/* we now need to adjust the metrics according to the change in */
/* width/positioning that occurred during the hinting process */
if ( scaler.render_mode != FT_RENDER_MODE_LIGHT )
{
AF_AxisHints axis = &hints->axis[AF_DIMENSION_HORZ];
if ( axis->num_edges > 1 && AF_HINTS_DO_ADVANCE( hints ) )
{
AF_Edge edge1 = axis->edges; /* leftmost edge */
AF_Edge edge2 = edge1 +
axis->num_edges - 1; /* rightmost edge */
FT_Pos old_rsb = loader->pp2.x - edge2->opos;
/* loader->pp1.x is always zero at this point of time */
FT_Pos old_lsb = edge1->opos; /* - loader->pp1.x */
FT_Pos new_lsb = edge1->pos;
/* remember unhinted values to later account */
/* for rounding errors */
FT_Pos pp1x_uh = new_lsb - old_lsb;
FT_Pos pp2x_uh = edge2->pos + old_rsb;
/* prefer too much space over too little space */
/* for very small sizes */
if ( old_lsb < 24 )
pp1x_uh -= 8;
if ( old_rsb < 24 )
pp2x_uh += 8;
loader->pp1.x = FT_PIX_ROUND( pp1x_uh );
loader->pp2.x = FT_PIX_ROUND( pp2x_uh );
if ( loader->pp1.x >= new_lsb && old_lsb > 0 )
loader->pp1.x -= 64;
if ( loader->pp2.x <= edge2->pos && old_rsb > 0 )
loader->pp2.x += 64;
slot->lsb_delta = loader->pp1.x - pp1x_uh;
slot->rsb_delta = loader->pp2.x - pp2x_uh;
}
else
{
FT_Pos pp1x = loader->pp1.x;
FT_Pos pp2x = loader->pp2.x;
loader->pp1.x = FT_PIX_ROUND( pp1x );
loader->pp2.x = FT_PIX_ROUND( pp2x );
slot->lsb_delta = loader->pp1.x - pp1x;
slot->rsb_delta = loader->pp2.x - pp2x;
}
}
/* `light' mode uses integer advance widths */
/* but sets `lsb_delta' and `rsb_delta' */
else
{
FT_Pos pp1x = loader->pp1.x;
FT_Pos pp2x = loader->pp2.x;
loader->pp1.x = FT_PIX_ROUND( pp1x );
loader->pp2.x = FT_PIX_ROUND( pp2x );
slot->lsb_delta = loader->pp1.x - pp1x;
slot->rsb_delta = loader->pp2.x - pp2x;
}
break;
default:
/* we don't support other formats (yet?) */
error = FT_THROW( Unimplemented_Feature );
}
Hint_Metrics:
{
FT_BBox bbox;
FT_Vector vvector;
vvector.x = slot->metrics.vertBearingX - slot->metrics.horiBearingX;
vvector.y = slot->metrics.vertBearingY - slot->metrics.horiBearingY;
vvector.x = FT_MulFix( vvector.x, style_metrics->scaler.x_scale );
vvector.y = FT_MulFix( vvector.y, style_metrics->scaler.y_scale );
/* transform the hinted outline if needed */
if ( loader->transformed )
{
FT_Outline_Transform( &gloader->base.outline, &loader->trans_matrix );
FT_Vector_Transform( &vvector, &loader->trans_matrix );
}
/* we must translate our final outline by -pp1.x and compute */
/* the new metrics */
if ( loader->pp1.x )
FT_Outline_Translate( &gloader->base.outline, -loader->pp1.x, 0 );
FT_Outline_Get_CBox( &gloader->base.outline, &bbox );
bbox.xMin = FT_PIX_FLOOR( bbox.xMin );
bbox.yMin = FT_PIX_FLOOR( bbox.yMin );
bbox.xMax = FT_PIX_CEIL( bbox.xMax );
bbox.yMax = FT_PIX_CEIL( bbox.yMax );
slot->metrics.width = bbox.xMax - bbox.xMin;
slot->metrics.height = bbox.yMax - bbox.yMin;
slot->metrics.horiBearingX = bbox.xMin;
slot->metrics.horiBearingY = bbox.yMax;
slot->metrics.vertBearingX = FT_PIX_FLOOR( bbox.xMin + vvector.x );
slot->metrics.vertBearingY = FT_PIX_FLOOR( bbox.yMax + vvector.y );
/* for mono-width fonts (like Andale, Courier, etc.) we need */
/* to keep the original rounded advance width; ditto for */
/* digits if all have the same advance width */
if ( scaler.render_mode != FT_RENDER_MODE_LIGHT &&
( FT_IS_FIXED_WIDTH( slot->face ) ||
( af_face_globals_is_digit( loader->globals, glyph_index ) &&
style_metrics->digits_have_same_width ) ) )
{
slot->metrics.horiAdvance =
FT_MulFix( slot->metrics.horiAdvance,
style_metrics->scaler.x_scale );
/* Set delta values to 0. Otherwise code that uses them is */
/* going to ruin the fixed advance width. */
slot->lsb_delta = 0;
slot->rsb_delta = 0;
}
else
{
/* non-spacing glyphs must stay as-is */
if ( slot->metrics.horiAdvance )
slot->metrics.horiAdvance = loader->pp2.x - loader->pp1.x;
}
slot->metrics.vertAdvance = FT_MulFix( slot->metrics.vertAdvance,
style_metrics->scaler.y_scale );
slot->metrics.horiAdvance = FT_PIX_ROUND( slot->metrics.horiAdvance );
slot->metrics.vertAdvance = FT_PIX_ROUND( slot->metrics.vertAdvance );
slot->format = FT_GLYPH_FORMAT_OUTLINE;
}
Exit:
return error;
}
/*
* Compute amount of font units the face should be emboldened by, in
* analogy to the CFF driver's `cf2_computeDarkening' function. See there
* for details of the algorithm.
*
* XXX: Currently a crude adaption of the original algorithm. Do better?
*/
FT_LOCAL_DEF( FT_Fixed )
af_loader_compute_darkening( AF_Loader loader,
FT_Face face,
FT_Pos standard_width )
{
AF_Module module = loader->globals->module;
FT_UShort units_per_EM;
FT_Fixed ppem, em_ratio;
FT_Fixed stem_width, stem_width_per_1000, scaled_stem, darken_amount;
FT_Int log_base_2;
FT_Int x1, y1, x2, y2, x3, y3, x4, y4;
ppem = FT_MAX( af_intToFixed( 4 ),
af_intToFixed( face->size->metrics.x_ppem ) );
units_per_EM = face->units_per_EM;
em_ratio = FT_DivFix( af_intToFixed( 1000 ),
af_intToFixed ( units_per_EM ) );
if ( em_ratio < af_floatToFixed( .01 ) )
{
/* If something goes wrong, don't embolden. */
return 0;
}
x1 = module->darken_params[0];
y1 = module->darken_params[1];
x2 = module->darken_params[2];
y2 = module->darken_params[3];
x3 = module->darken_params[4];
y3 = module->darken_params[5];
x4 = module->darken_params[6];
y4 = module->darken_params[7];
if ( standard_width <= 0 )
{
stem_width = af_intToFixed( 75 ); /* taken from cf2font.c */
stem_width_per_1000 = stem_width;
}
else
{
stem_width = af_intToFixed( standard_width );
stem_width_per_1000 = FT_MulFix( stem_width, em_ratio );
}
log_base_2 = FT_MSB( (FT_UInt32)stem_width_per_1000 ) +
FT_MSB( (FT_UInt32)ppem );
if ( log_base_2 >= 46 )
{
/* possible overflow */
scaled_stem = af_intToFixed( x4 );
}
else
scaled_stem = FT_MulFix( stem_width_per_1000, ppem );
/* now apply the darkening parameters */
if ( scaled_stem < af_intToFixed( x1 ) )
darken_amount = FT_DivFix( af_intToFixed( y1 ), ppem );
else if ( scaled_stem < af_intToFixed( x2 ) )
{
FT_Int xdelta = x2 - x1;
FT_Int ydelta = y2 - y1;
FT_Int x = stem_width_per_1000 -
FT_DivFix( af_intToFixed( x1 ), ppem );
if ( !xdelta )
goto Try_x3;
darken_amount = FT_MulDiv( x, ydelta, xdelta ) +
FT_DivFix( af_intToFixed( y1 ), ppem );
}
else if ( scaled_stem < af_intToFixed( x3 ) )
{
Try_x3:
{
FT_Int xdelta = x3 - x2;
FT_Int ydelta = y3 - y2;
FT_Int x = stem_width_per_1000 -
FT_DivFix( af_intToFixed( x2 ), ppem );
if ( !xdelta )
goto Try_x4;
darken_amount = FT_MulDiv( x, ydelta, xdelta ) +
FT_DivFix( af_intToFixed( y2 ), ppem );
}
}
else if ( scaled_stem < af_intToFixed( x4 ) )
{
Try_x4:
{
FT_Int xdelta = x4 - x3;
FT_Int ydelta = y4 - y3;
FT_Int x = stem_width_per_1000 -
FT_DivFix( af_intToFixed( x3 ), ppem );
if ( !xdelta )
goto Use_y4;
darken_amount = FT_MulDiv( x, ydelta, xdelta ) +
FT_DivFix( af_intToFixed( y3 ), ppem );
}
}
else
{
Use_y4:
darken_amount = FT_DivFix( af_intToFixed( y4 ), ppem );
}
/* Convert darken_amount from per 1000 em to true character space. */
return FT_DivFix( darken_amount, em_ratio );
}
/* END */