freetype中FT_Set_Transform（）和FT_Load_Char（）分析（待续）
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在程序中：
………………
pen.x = 0 * 64;
pen.y = ( target_height - 70 ) * 64;
FT_Set_Transform( face, 0, &pen );
error = FT_Load_Char( face, text[n], FT_LOAD_RENDER ); （渲染的位图会根据pen，设置好face->glyph->bitmap_left和tbitmap_top）
………………
先设置了pen的x和y值，然后执行FT_Set_Transform（）。我们进入FT_Set_Transform（）分析。
1( void )2 FT_Set_Transform( FT_Face face,3 FT_Matrix* matrix,4 FT_Vector* delta )5 {6 FT_Face_Internal internal;789 if ( !face )10 return;1112 internal = face->internal;1314 internal->transform_flags = 0;1516 if ( !matrix )17 {18 internal->transform_matrix.xx = 0x10000L;19 internal->transform_matrix.xy = 0;20 internal->transform_matrix.yx = 0;21 internal->transform_matrix.yy = 0x10000L;22 matrix = &internal->transform_matrix;23 }24 else25 internal->transform_matrix = *matrix;2627 /* set transform_flags bit flag 0 if `matrix' isn't the identity */28 if ( ( matrix->xy | matrix->yx ) ||29 matrix->xx != 0x10000L ||30 matrix->yy != 0x10000L )31 internal->transform_flags |= 1;3233 if ( !delta )34 {35 internal->transform_delta.x = 0;36 internal->transform_delta.y = 0;37 delta = &internal->transform_delta;38 }39 else40 internal->transform_delta = *delta;4142 /* set transform_flags bit flag 1 if `delta' isn't the null vector */43 if ( delta->x | delta->y )44 internal->transform_flags |= 2;45 }第9行判断是否有face，如果不存在则出错。第16行判断是否有matrix（矩阵变换），不存在时按默认设置。
第33行当传入delta时按照它设置face->internal->transform_delta。
继续分析程序中的FT_Load_Char：
1( FT_Error )2 FT_Load_Char( FT_Face face,3 FT_ULong char_code,4 FT_Int32 load_flags )5 {6 FT_UInt glyph_index;789 if ( !face )10 return FT_Err_Invalid_Face_Handle;1112 glyph_index = (FT_UInt)char_code;13 if ( face->charmap )14 glyph_index = FT_Get_Char_Index( face, char_code );1516 return FT_Load_Glyph( face, glyph_index, load_flags );17 }当存在face时，调用了FT_Load_Glyph来加载位图。我们进入FT_Load_Glyph中：
1 FT_EXPORT_DEF( FT_Error )2 FT_Load_Glyph( FT_Face face,3 FT_UInt glyph_index,4 FT_Int32 load_flags )5 {6 FT_Error error;7 FT_Driver driver;8 FT_GlyphSlot slot;9 FT_Library library;10 FT_Bool autohint = FALSE;11 FT_Module hinter;12 TT_Face ttface = (TT_Face)face;131415 if ( !face || !face->size || !face->glyph )16 return FT_Err_Invalid_Face_Handle;1718 /* The validity test for `glyph_index' is performed by the */19 /* font drivers. */2021 slot = face->glyph;22 ft_glyphslot_clear( slot );2324 driver = face->driver;25 library = driver->root.library;26 hinter = library->auto_hinter;2728 /* resolve load flags dependencies */2930 if ( load_flags & FT_LOAD_NO_RECURSE )31 load_flags |= FT_LOAD_NO_SCALE |32 FT_LOAD_IGNORE_TRANSFORM;3334 if ( load_flags & FT_LOAD_NO_SCALE )35 {36 load_flags |= FT_LOAD_NO_HINTING |37 FT_LOAD_NO_BITMAP;3839 load_flags &= ~FT_LOAD_RENDER;40 }4142 /*43 * Determine whether we need to auto-hint or not.44 * The general rules are:45 *46 * - Do only auto-hinting if we have a hinter module, a scalable font47 * format dealing with outlines, and no transforms except simple48 * slants and/or rotations by integer multiples of 90 degrees.49 *50 * - Then, auto-hint if FT_LOAD_FORCE_AUTOHINT is set or if we don't51 * have a native font hinter.52 *53 * - Otherwise, auto-hint for LIGHT hinting mode or if there isn't54 * any hinting bytecode in the TrueType/OpenType font.55 *56 * - Exception: The font is `tricky' and requires the native hinter to57 * load properly.58 */5960 if ( hinter &&61 !( load_flags & FT_LOAD_NO_HINTING ) &&62 !( load_flags & FT_LOAD_NO_AUTOHINT ) &&63 FT_DRIVER_IS_SCALABLE( driver ) &&64 FT_DRIVER_USES_OUTLINES( driver ) &&65 !FT_IS_TRICKY( face ) &&66 ( ( load_flags & FT_LOAD_IGNORE_TRANSFORM ) || ( face->internal->transform_matrix.yx == 0 && face->internal->transform_matrix.xx != 0 ) || ( face->internal->transform_matrix.xx == 0 && face->internal->transform_matrix.yx != 0 ) ) ) { if ( ( load_flags & FT_LOAD_FORCE_AUTOHINT ) || !FT_DRIVER_HAS_HINTER( driver ) ) autohint = TRUE; else { FT_Render_Mode mode = FT_LOAD_TARGET_MODE( load_flags ); /* the check for `num_locations' assures that we actually */ /* test for instructions in a TTF and not in a CFF-based OTF */ if ( mode == FT_RENDER_MODE_LIGHT || face->internal->ignore_unpatented_hinter || ( FT_IS_SFNT( face ) && ttface->num_locations && ttface->max_profile.maxSizeOfInstructions == 0 ) ) autohint = TRUE; } } if ( autohint ) { FT_AutoHinter_Service hinting; /* try to load embedded bitmaps first if available */ /* */ /* XXX: This is really a temporary hack that should disappear */ /* promptly with FreeType 2.1! */ /* */ if ( FT_HAS_FIXED_SIZES( face ) && ( load_flags & FT_LOAD_NO_BITMAP ) == 0 ) { error = driver->clazz->load_glyph( slot, face->size, glyph_index, load_flags | FT_LOAD_SBITS_ONLY ); if ( !error && slot->format == FT_GLYPH_FORMAT_BITMAP ) goto Load_Ok; } { FT_Face_Internal internal = face->internal; FT_Int transform_flags = internal->transform_flags; /* since the auto-hinter calls FT_Load_Glyph by itself, */ /* make sure that glyphs aren't transformed */ internal->transform_flags = 0; /* load auto-hinted outline */ hinting = (FT_AutoHinter_Service)hinter->clazz->module_interface; error = hinting->load_glyph( (FT_AutoHinter)hinter, slot, face->size, glyph_index, load_flags ); internal->transform_flags = transform_flags; } } else { error = driver->clazz->load_glyph( slot, face->size, glyph_index, load_flags ); if ( error ) goto Exit; if ( slot->format == FT_GLYPH_FORMAT_OUTLINE ) { /* check that the loaded outline is correct */ error = FT_Outline_Check( &slot->outline ); if ( error ) goto Exit;#ifdef GRID_FIT_METRICS if ( !( load_flags & FT_LOAD_NO_HINTING ) ) ft_glyphslot_grid_fit_metrics( slot, FT_BOOL( load_flags & FT_LOAD_VERTICAL_LAYOUT ) );#endif } } Load_Ok: /* compute the advance */ if ( load_flags & FT_LOAD_VERTICAL_LAYOUT ) { slot->advance.x = 0; slot->advance.y = slot->metrics.vertAdvance; } else { slot->advance.x = slot->metrics.horiAdvance; slot->advance.y = 0; } /* compute the linear advance in 16.16 pixels */ if ( ( load_flags & FT_LOAD_LINEAR_DESIGN ) == 0 && ( FT_IS_SCALABLE( face ) ) ) { FT_Size_Metrics* metrics = &face->size->metrics; /* it's tricky! */ slot->linearHoriAdvance = FT_MulDiv( slot->linearHoriAdvance, metrics->x_scale, 64 ); slot->linearVertAdvance = FT_MulDiv( slot->linearVertAdvance, metrics->y_scale, 64 ); } if ( ( load_flags & FT_LOAD_IGNORE_TRANSFORM ) == 0 ) { FT_Face_Internal internal = face->internal; /* now, transform the glyph image if needed */ if ( internal->transform_flags ) { /* get renderer */ FT_Renderer renderer = ft_lookup_glyph_renderer( slot ); if ( renderer ) error = renderer->clazz->transform_glyph( renderer, slot, &internal->transform_matrix, &internal->transform_delta ); else if ( slot->format == FT_GLYPH_FORMAT_OUTLINE ) { /* apply `standard' transformation if no renderer is available */ if ( internal->transform_flags & 1 ) FT_Outline_Transform( &slot->outline, &internal->transform_matrix ); if ( internal->transform_flags & 2 ) FT_Outline_Translate( &slot->outline, internal->transform_delta.x, internal->transform_delta.y ); } /* transform advance */ FT_Vector_Transform( &slot->advance, &internal->transform_matrix ); } } FT_TRACE5(( " x advance: %d\n" , slot->advance.x )); FT_TRACE5(( " y advance: %d\n" , slot->advance.y )); FT_TRACE5(( " linear x advance: %d\n" , slot->linearHoriAdvance )); FT_TRACE5(( " linear y advance: %d\n" , slot->linearVertAdvance )); /* do we need to render the image now? */ if ( !error && slot->format != FT_GLYPH_FORMAT_BITMAP && slot->format != FT_GLYPH_FORMAT_COMPOSITE && load_flags & FT_LOAD_RENDER ) { FT_Render_Mode mode = FT_LOAD_TARGET_MODE( load_flags ); if ( mode == FT_RENDER_MODE_NORMAL && (load_flags & FT_LOAD_MONOCHROME ) ) mode = FT_RENDER_MODE_MONO; error = FT_Render_Glyph( slot, mode ); } Exit: return error; } 0 0
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