Edit
kc3-lang/freetype/src/base/ftbbox.c
Werner Lemberg
- src/base/ftbbox.c
-
/***************************************************************************/ /* */ /* ftbbox.c */ /* */ /* FreeType bbox computation (body). */ /* */ /* Copyright 1996-2002, 2004, 2006, 2010, 2013 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. */ /* */ /***************************************************************************/ /*************************************************************************/ /* */ /* This component has a _single_ role: to compute exact outline bounding */ /* boxes. */ /* */ /*************************************************************************/ #include <ft2build.h> #include FT_INTERNAL_DEBUG_H #include FT_BBOX_H #include FT_IMAGE_H #include FT_OUTLINE_H #include FT_INTERNAL_CALC_H #include FT_INTERNAL_OBJECTS_H typedef struct TBBox_Rec_ { FT_Vector last; FT_BBox bbox; } TBBox_Rec; /*************************************************************************/ /* */ /* <Function> */ /* BBox_Move_To */ /* */ /* <Description> */ /* This function is used as a `move_to' and `line_to' emitter during */ /* FT_Outline_Decompose(). It simply records the destination point */ /* in `user->last'; no further computations are necessary since we */ /* use the cbox as the starting bbox which must be refined. */ /* */ /* <Input> */ /* to :: A pointer to the destination vector. */ /* */ /* <InOut> */ /* user :: A pointer to the current walk context. */ /* */ /* <Return> */ /* Always 0. Needed for the interface only. */ /* */ static int BBox_Move_To( FT_Vector* to, TBBox_Rec* user ) { user->last = *to; return 0; } #define CHECK_X( p, bbox ) \ ( p->x < bbox.xMin || p->x > bbox.xMax ) #define CHECK_Y( p, bbox ) \ ( p->y < bbox.yMin || p->y > bbox.yMax ) /*************************************************************************/ /* */ /* <Function> */ /* BBox_Conic_Check */ /* */ /* <Description> */ /* Find the extrema of a 1-dimensional conic Bezier curve and update */ /* a bounding range. This version uses direct computation, as it */ /* doesn't need square roots. */ /* */ /* <Input> */ /* y1 :: The start coordinate. */ /* */ /* y2 :: The coordinate of the control point. */ /* */ /* y3 :: The end coordinate. */ /* */ /* <InOut> */ /* min :: The address of the current minimum. */ /* */ /* max :: The address of the current maximum. */ /* */ static void BBox_Conic_Check( FT_Pos y1, FT_Pos y2, FT_Pos y3, FT_Pos* min, FT_Pos* max ) { /* This function is only called when a control off-point is outside */ /* the bbox that contains all on-points. It finds a local extremum */ /* within the segment, equal to (y1*y3 - y2*y2)/(y1 - 2*y2 + y3). */ /* Or, offsetting from y2, we get */ y1 -= y2; y3 -= y2; y2 += FT_MulDiv( y1, y3, y1 + y3 ); if ( y2 < *min ) *min = y2; if ( y2 > *max ) *max = y2; } /*************************************************************************/ /* */ /* <Function> */ /* BBox_Conic_To */ /* */ /* <Description> */ /* This function is used as a `conic_to' emitter during */ /* FT_Outline_Decompose(). It checks a conic Bezier curve with the */ /* current bounding box, and computes its extrema if necessary to */ /* update it. */ /* */ /* <Input> */ /* control :: A pointer to a control point. */ /* */ /* to :: A pointer to the destination vector. */ /* */ /* <InOut> */ /* user :: The address of the current walk context. */ /* */ /* <Return> */ /* Always 0. Needed for the interface only. */ /* */ /* <Note> */ /* In the case of a non-monotonous arc, we compute directly the */ /* extremum coordinates, as it is sufficiently fast. */ /* */ static int BBox_Conic_To( FT_Vector* control, FT_Vector* to, TBBox_Rec* user ) { /* we don't need to check `to' since it is always an `on' point, thus */ /* within the bbox */ if ( CHECK_X( control, user->bbox ) ) BBox_Conic_Check( user->last.x, control->x, to->x, &user->bbox.xMin, &user->bbox.xMax ); if ( CHECK_Y( control, user->bbox ) ) BBox_Conic_Check( user->last.y, control->y, to->y, &user->bbox.yMin, &user->bbox.yMax ); user->last = *to; return 0; } /*************************************************************************/ /* */ /* <Function> */ /* BBox_Cubic_Check */ /* */ /* <Description> */ /* Find the extrema of a 1-dimensional cubic Bezier curve and */ /* update a bounding range. This version uses iterative splitting */ /* because it is faster than the exact solution with square roots. */ /* */ /* <Input> */ /* p1 :: The start coordinate. */ /* */ /* p2 :: The coordinate of the first control point. */ /* */ /* p3 :: The coordinate of the second control point. */ /* */ /* p4 :: The end coordinate. */ /* */ /* <InOut> */ /* min :: The address of the current minimum. */ /* */ /* max :: The address of the current maximum. */ /* */ static FT_Pos update_cubic_max( FT_Pos q1, FT_Pos q2, FT_Pos q3, FT_Pos q4, FT_Pos max ) { /* for a cubic segment to possibly reach new maximum, at least */ /* one of its off-points must stay above the current value */ while ( q2 > max || q3 > max ) { /* determine which half contains the maximum and split */ if ( q1 + q2 > q3 + q4 ) /* first half */ { q4 = q4 + q3; q3 = q3 + q2; q2 = q2 + q1; q4 = q4 + q3; q3 = q3 + q2; q4 = ( q4 + q3 ) / 8; q3 = q3 / 4; q2 = q2 / 2; } else /* second half */ { q1 = q1 + q2; q2 = q2 + q3; q3 = q3 + q4; q1 = q1 + q2; q2 = q2 + q3; q1 = ( q1 + q2 ) / 8; q2 = q2 / 4; q3 = q3 / 2; } /* check whether either end reached the maximum */ if ( q1 == q2 && q1 >= q3 ) { max = q1; break; } if ( q3 == q4 && q2 <= q4 ) { max = q4; break; } } return max; } static void BBox_Cubic_Check( FT_Pos p1, FT_Pos p2, FT_Pos p3, FT_Pos p4, FT_Pos* min, FT_Pos* max ) { FT_Pos nmin, nmax; FT_Int shift; /* This function is only called when a control off-point is outside */ /* the bbox that contains all on-points. It finds a local extremum */ /* within the segment using iterative bisection of the segment. */ /* The fixed-point arithmetic of bisection is inherently stable */ /* but may loose accuracy in the two lowest bits. To compensate, */ /* we upscale the segment if there is room. Large values may need */ /* to be downscaled to avoid overflows during bisection. */ /* The control off-point outside the bbox is likely to have the top */ /* absolute value among arguments. */ shift = 27 - FT_MSB( FT_ABS( p2 ) | FT_ABS( p3 ) ); if ( shift > 0 ) { /* upscaling too much just wastes time */ if ( shift > 2 ) shift = 2; p1 <<= shift; p2 <<= shift; p3 <<= shift; p4 <<= shift; nmin = *min << shift; nmax = *max << shift; } else { p1 >>= -shift; p2 >>= -shift; p3 >>= -shift; p4 >>= -shift; nmin = *min >> -shift; nmax = *max >> -shift; } nmax = update_cubic_max( p1, p2, p3, p4, nmax ); /* now flip the signs to update the minimum */ nmin = -update_cubic_max( -p1, -p2, -p3, -p4, -nmin ); if ( shift > 0 ) { nmin >>= shift; nmax >>= shift; } else { nmin <<= -shift; nmax <<= -shift; } if ( nmin < *min ) *min = nmin; if ( nmax > *max ) *max = nmax; } /*************************************************************************/ /* */ /* <Function> */ /* BBox_Cubic_To */ /* */ /* <Description> */ /* This function is used as a `cubic_to' emitter during */ /* FT_Outline_Decompose(). It checks a cubic Bezier curve with the */ /* current bounding box, and computes its extrema if necessary to */ /* update it. */ /* */ /* <Input> */ /* control1 :: A pointer to the first control point. */ /* */ /* control2 :: A pointer to the second control point. */ /* */ /* to :: A pointer to the destination vector. */ /* */ /* <InOut> */ /* user :: The address of the current walk context. */ /* */ /* <Return> */ /* Always 0. Needed for the interface only. */ /* */ /* <Note> */ /* In the case of a non-monotonous arc, we don't compute directly */ /* extremum coordinates, we subdivide instead. */ /* */ static int BBox_Cubic_To( FT_Vector* control1, FT_Vector* control2, FT_Vector* to, TBBox_Rec* user ) { /* We don't need to check `to' since it is always an on-point, */ /* thus within the bbox. Only segments with an off-point outside */ /* the bbox can possibly reach new extreme values. */ if ( CHECK_X( control1, user->bbox ) || CHECK_X( control2, user->bbox ) ) BBox_Cubic_Check( user->last.x, control1->x, control2->x, to->x, &user->bbox.xMin, &user->bbox.xMax ); if ( CHECK_Y( control1, user->bbox ) || CHECK_Y( control2, user->bbox ) ) BBox_Cubic_Check( user->last.y, control1->y, control2->y, to->y, &user->bbox.yMin, &user->bbox.yMax ); user->last = *to; return 0; } FT_DEFINE_OUTLINE_FUNCS(bbox_interface, (FT_Outline_MoveTo_Func) BBox_Move_To, (FT_Outline_LineTo_Func) BBox_Move_To, (FT_Outline_ConicTo_Func)BBox_Conic_To, (FT_Outline_CubicTo_Func)BBox_Cubic_To, 0, 0 ) /* documentation is in ftbbox.h */ FT_EXPORT_DEF( FT_Error ) FT_Outline_Get_BBox( FT_Outline* outline, FT_BBox *abbox ) { FT_BBox cbox; FT_BBox bbox; FT_Vector* vec; FT_UShort n; if ( !abbox ) return FT_THROW( Invalid_Argument ); if ( !outline ) return FT_THROW( Invalid_Outline ); /* if outline is empty, return (0,0,0,0) */ if ( outline->n_points == 0 || outline->n_contours <= 0 ) { abbox->xMin = abbox->xMax = 0; abbox->yMin = abbox->yMax = 0; return 0; } /* We compute the control box as well as the bounding box of */ /* all `on' points in the outline. Then, if the two boxes */ /* coincide, we exit immediately. */ vec = outline->points; bbox.xMin = bbox.xMax = cbox.xMin = cbox.xMax = vec->x; bbox.yMin = bbox.yMax = cbox.yMin = cbox.yMax = vec->y; vec++; for ( n = 1; n < outline->n_points; n++ ) { FT_Pos x = vec->x; FT_Pos y = vec->y; /* update control box */ if ( x < cbox.xMin ) cbox.xMin = x; if ( x > cbox.xMax ) cbox.xMax = x; if ( y < cbox.yMin ) cbox.yMin = y; if ( y > cbox.yMax ) cbox.yMax = y; if ( FT_CURVE_TAG( outline->tags[n] ) == FT_CURVE_TAG_ON ) { /* update bbox for `on' points only */ if ( x < bbox.xMin ) bbox.xMin = x; if ( x > bbox.xMax ) bbox.xMax = x; if ( y < bbox.yMin ) bbox.yMin = y; if ( y > bbox.yMax ) bbox.yMax = y; } vec++; } /* test two boxes for equality */ if ( cbox.xMin < bbox.xMin || cbox.xMax > bbox.xMax || cbox.yMin < bbox.yMin || cbox.yMax > bbox.yMax ) { /* the two boxes are different, now walk over the outline to */ /* get the Bezier arc extrema. */ FT_Error error; TBBox_Rec user; #ifdef FT_CONFIG_OPTION_PIC FT_Outline_Funcs bbox_interface; Init_Class_bbox_interface(&bbox_interface); #endif user.bbox = bbox; error = FT_Outline_Decompose( outline, &bbox_interface, &user ); if ( error ) return error; *abbox = user.bbox; } else *abbox = bbox; return FT_Err_Ok; } /* END */