diff options
Diffstat (limited to 'src/autofit/afloader.c')
| -rw-r--r-- | src/autofit/afloader.c | 271 |
1 files changed, 270 insertions, 1 deletions
diff --git a/src/autofit/afloader.c b/src/autofit/afloader.c index 7c2fa7c..aa5b8fd 100644 --- a/src/autofit/afloader.c +++ b/src/autofit/afloader.c @@ -23,6 +23,8 @@ #include "afmodule.h" #include "afpic.h" +#include FT_INTERNAL_CALC_H + /* Initialize glyph loader. */ @@ -76,6 +78,14 @@ } +#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 ) ) + + /* 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. */ @@ -88,6 +98,8 @@ FT_UInt glyph_index, FT_Int32 load_flags ) { + AF_Module module = loader->globals->module; + FT_Error error; FT_Face face = loader->face; AF_StyleMetrics metrics = loader->metrics; @@ -103,6 +115,132 @@ 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. + */ + if ( !module->no_stem_darkening ) + { + AF_FaceGlobals globals = loader->globals; + AF_WritingSystemClass writing_system_class; + + FT_Pos stdVW = 0; + FT_Pos stdHW = 0; + + FT_Bool size_changed = face->size->metrics.x_ppem + != globals->stem_darkening_for_ppem; + + FT_Fixed em_size = af_intToFixed( face->units_per_EM ); + FT_Fixed em_ratio = FT_DivFix( af_intToFixed( 1000 ), em_size ); + + FT_Matrix scale_down_matrix = { 0x10000L, 0, 0, 0x10000L }; + + + /* Skip stem darkening for broken fonts. */ + if ( !face->units_per_EM ) + goto After_Emboldening; + + /* + * 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 effectively disabled. + */ + writing_system_class = + AF_WRITING_SYSTEM_CLASSES_GET[metrics->style_class->writing_system]; + + if ( writing_system_class->style_metrics_getstdw ) + writing_system_class->style_metrics_getstdw( metrics, + &stdHW, + &stdVW ); + else + goto After_Emboldening; + + + 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_intToFixed( af_loader_compute_darkening( loader, + face, + stdVW ) ); + darken_x = FT_DivFix( FT_MulFix( darken_by_font_units_x, + face->size->metrics.x_scale ), + em_ratio ); + + globals->standard_vertical_width = stdVW; + globals->stem_darkening_for_ppem = face->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_intToFixed( af_loader_compute_darkening( loader, + face, + stdHW ) ); + darken_y = FT_DivFix( FT_MulFix( darken_by_font_units_y, + face->size->metrics.y_scale ), + em_ratio ); + + globals->standard_horizontal_width = stdHW; + globals->stem_darkening_for_ppem = face->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 ); + } + + After_Emboldening: loader->transformed = internal->glyph_transformed; if ( loader->transformed ) { @@ -150,7 +288,8 @@ if ( writing_system_class->style_hints_apply ) - writing_system_class->style_hints_apply( hints, + writing_system_class->style_hints_apply( glyph_index, + hints, &gloader->base.outline, metrics ); } @@ -404,4 +543,134 @@ } + /* + * 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_Int32 ) + 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 af_fixedToInt( FT_DivFix( darken_amount, em_ratio ) ); + } + + /* END */ |