| /***************************************************************************/ |
| /* */ |
| /* 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 */ |
