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Diffstat (limited to 'modules/freetype2/src/base/ftbbox.c')
| -rw-r--r-- | modules/freetype2/src/base/ftbbox.c | 530 |
1 files changed, 530 insertions, 0 deletions
diff --git a/modules/freetype2/src/base/ftbbox.c b/modules/freetype2/src/base/ftbbox.c new file mode 100644 index 0000000000..7dd71882ea --- /dev/null +++ b/modules/freetype2/src/base/ftbbox.c @@ -0,0 +1,530 @@ +/**************************************************************************** + * + * ftbbox.c + * + * FreeType bbox computation (body). + * + * Copyright (C) 1996-2023 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 <freetype/internal/ftdebug.h> + +#include <freetype/ftbbox.h> +#include <freetype/ftimage.h> +#include <freetype/ftoutln.h> +#include <freetype/internal/ftcalc.h> +#include <freetype/internal/ftobjs.h> + + + typedef struct TBBox_Rec_ + { + FT_Vector last; + FT_BBox bbox; + + } TBBox_Rec; + + +#define FT_UPDATE_BBOX( p, bbox ) \ + FT_BEGIN_STMNT \ + if ( p->x < bbox.xMin ) \ + bbox.xMin = p->x; \ + if ( p->x > bbox.xMax ) \ + bbox.xMax = p->x; \ + if ( p->y < bbox.yMin ) \ + bbox.yMin = p->y; \ + if ( p->y > bbox.yMax ) \ + bbox.yMax = p->y; \ + FT_END_STMNT + +#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_Move_To + * + * @Description: + * This function is used as a `move_to' emitter during + * FT_Outline_Decompose(). It simply records the destination point + * in `user->last'. We also update bbox in case contour starts with + * an implicit `on' point. + * + * @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 ) + { + FT_UPDATE_BBOX( to, user->bbox ); + + user->last = *to; + + return 0; + } + + + /************************************************************************** + * + * @Function: + * BBox_Line_To + * + * @Description: + * This function is used as a `line_to' emitter during + * FT_Outline_Decompose(). It simply records the destination point + * in `user->last'; no further computations are necessary because + * bbox already contains both explicit ends of the line segment. + * + * @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_Line_To( FT_Vector* to, + TBBox_Rec* user ) + { + user->last = *to; + + return 0; + } + + + /************************************************************************** + * + * @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 ) + { + /* in case `to' is implicit and not included in bbox yet */ + FT_UPDATE_BBOX( to, user->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 + cubic_peak( FT_Pos q1, + FT_Pos q2, + FT_Pos q3, + FT_Pos q4 ) + { + FT_Pos peak = 0; + FT_Int shift; + + + /* This function finds a peak of a cubic segment if it is above 0 */ + /* using iterative bisection of the segment, or returns 0. */ + /* 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. */ + /* It is called with either q2 or q3 positive, which is necessary */ + /* for the peak to exist and avoids undefined FT_MSB. */ + + shift = 27 - FT_MSB( (FT_UInt32)( FT_ABS( q1 ) | + FT_ABS( q2 ) | + FT_ABS( q3 ) | + FT_ABS( q4 ) ) ); + + if ( shift > 0 ) + { + /* upscaling too much just wastes time */ + if ( shift > 2 ) + shift = 2; + + q1 *= 1 << shift; + q2 *= 1 << shift; + q3 *= 1 << shift; + q4 *= 1 << shift; + } + else + { + q1 >>= -shift; + q2 >>= -shift; + q3 >>= -shift; + q4 >>= -shift; + } + + /* for a peak to exist above 0, the cubic segment must have */ + /* at least one of its control off-points above 0. */ + while ( q2 > 0 || q3 > 0 ) + { + /* 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 ) >> 3; + q3 = q3 >> 2; + q2 = q2 >> 1; + } + else /* second half */ + { + q1 = q1 + q2; + q2 = q2 + q3; + q3 = q3 + q4; + q1 = q1 + q2; + q2 = q2 + q3; + q1 = ( q1 + q2 ) >> 3; + q2 = q2 >> 2; + q3 = q3 >> 1; + } + + /* check whether either end reached the maximum */ + if ( q1 == q2 && q1 >= q3 ) + { + peak = q1; + break; + } + if ( q3 == q4 && q2 <= q4 ) + { + peak = q4; + break; + } + } + + if ( shift > 0 ) + peak >>= shift; + else + peak <<= -shift; + + return peak; + } + + + static void + BBox_Cubic_Check( FT_Pos p1, + FT_Pos p2, + FT_Pos p3, + FT_Pos p4, + 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. So at least one of the */ + /* conditions below holds and cubic_peak is called with at least one */ + /* non-zero argument. */ + + if ( p2 > *max || p3 > *max ) + *max += cubic_peak( p1 - *max, p2 - *max, p3 - *max, p4 - *max ); + + /* now flip the signs to update the minimum */ + if ( p2 < *min || p3 < *min ) + *min -= cubic_peak( *min - p1, *min - p2, *min - p3, *min - p4 ); + } + + + /************************************************************************** + * + * @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, /* move_to */ + (FT_Outline_LineTo_Func) BBox_Line_To, /* line_to */ + (FT_Outline_ConicTo_Func)BBox_Conic_To, /* conic_to */ + (FT_Outline_CubicTo_Func)BBox_Cubic_To, /* cubic_to */ + 0, /* shift */ + 0 /* delta */ + ) + + + /* documentation is in ftbbox.h */ + + FT_EXPORT_DEF( FT_Error ) + FT_Outline_Get_BBox( FT_Outline* outline, + FT_BBox *abbox ) + { + FT_BBox cbox = { 0x7FFFFFFFL, 0x7FFFFFFFL, + -0x7FFFFFFFL, -0x7FFFFFFFL }; + FT_BBox bbox = { 0x7FFFFFFFL, 0x7FFFFFFFL, + -0x7FFFFFFFL, -0x7FFFFFFFL }; + 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; + + for ( n = 0; n < outline->n_points; n++ ) + { + FT_UPDATE_BBOX( vec, cbox ); + + if ( FT_CURVE_TAG( outline->tags[n] ) == FT_CURVE_TAG_ON ) + FT_UPDATE_BBOX( vec, bbox ); + + 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; + + + 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 */ |