147 lines
4.7 KiB
C
147 lines
4.7 KiB
C
/*
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Bitmask 1.7 - A pixel-perfect collision detection library.
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Copyright (C) 2002-2005 Ulf Ekstrom except for the bitcount
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function which is copyright (C) Donald W. Gillies, 1992.
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public
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License as published by the Free Software Foundation; either
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version 2 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with this library; if not, write to the Free
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#ifndef BITMASK_H
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#define BITMASK_H
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#ifdef __cplusplus
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extern "C" {
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#endif
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#include <limits.h>
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/* Define INLINE for different compilers. If your compiler does not
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support inlining then there might be a performance hit in
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bitmask_overlap_area().
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*/
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#ifndef INLINE
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# ifdef __GNUC__
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# define INLINE inline
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# else
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# ifdef _MSC_VER
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# define INLINE __inline
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# else
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# define INLINE
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# endif
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# endif
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#endif
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#define BITMASK_W unsigned long int
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#define BITMASK_W_LEN (sizeof(BITMASK_W)*CHAR_BIT)
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#define BITMASK_W_MASK (BITMASK_W_LEN - 1)
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#define BITMASK_N(n) ((BITMASK_W)1 << (n))
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typedef struct bitmask
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{
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int w,h;
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BITMASK_W bits[1];
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} bitmask_t;
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/* Creates a bitmask of width w and height h, where
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w and h must both be greater than 0.
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The mask is automatically cleared when created.
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*/
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bitmask_t *bitmask_create(int w, int h);
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/* Frees all the memory allocated by bitmask_create for m. */
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void bitmask_free(bitmask_t *m);
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/* Clears all bits in the mask */
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void bitmask_clear(bitmask_t *m);
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/* Sets all bits in the mask */
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void bitmask_fill(bitmask_t *m);
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/* Flips all bits in the mask */
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void bitmask_invert(bitmask_t *m);
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/* Counts the bits in the mask */
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unsigned int bitmask_count(bitmask_t *m);
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/* Returns nonzero if the bit at (x,y) is set. Coordinates start at
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(0,0) */
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static INLINE int bitmask_getbit(const bitmask_t *m, int x, int y)
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{
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return (m->bits[x/BITMASK_W_LEN*m->h + y] & BITMASK_N(x & BITMASK_W_MASK)) != 0;
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}
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/* Sets the bit at (x,y) */
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static INLINE void bitmask_setbit(bitmask_t *m, int x, int y)
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{
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m->bits[x/BITMASK_W_LEN*m->h + y] |= BITMASK_N(x & BITMASK_W_MASK);
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}
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/* Clears the bit at (x,y) */
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static INLINE void bitmask_clearbit(bitmask_t *m, int x, int y)
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{
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m->bits[x/BITMASK_W_LEN*m->h + y] &= ~BITMASK_N(x & BITMASK_W_MASK);
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}
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/* Returns nonzero if the masks overlap with the given offset.
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The overlap tests uses the following offsets (which may be negative):
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+----+----------..
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|A | yoffset
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| +-+----------..
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+--|B
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|xoffset
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: :
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*/
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int bitmask_overlap(const bitmask_t *a, const bitmask_t *b, int xoffset, int yoffset);
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/* Like bitmask_overlap(), but will also give a point of intersection.
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x and y are given in the coordinates of mask a, and are untouched
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if there is no overlap. */
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int bitmask_overlap_pos(const bitmask_t *a, const bitmask_t *b,
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int xoffset, int yoffset, int *x, int *y);
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/* Returns the number of overlapping 'pixels' */
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int bitmask_overlap_area(const bitmask_t *a, const bitmask_t *b, int xoffset, int yoffset);
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/* Fills a mask with the overlap of two other masks. A bitwise AND. */
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void bitmask_overlap_mask (const bitmask_t *a, const bitmask_t *b, bitmask_t *c, int xoffset, int yoffset);
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/* Draws mask b onto mask a (bitwise OR). Can be used to compose large
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(game background?) mask from several submasks, which may speed up
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the testing. */
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void bitmask_draw(bitmask_t *a, const bitmask_t *b, int xoffset, int yoffset);
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void bitmask_erase(bitmask_t *a, const bitmask_t *b, int xoffset, int yoffset);
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/* Return a new scaled bitmask, with dimensions w*h. The quality of the
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scaling may not be perfect for all circumstances, but it should
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be reasonable. If either w or h is 0 a clear 1x1 mask is returned. */
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bitmask_t *bitmask_scale(const bitmask_t *m, int w, int h);
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/* Convolve b into a, drawing the output into o, shifted by offset. If offset
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* is 0, then the (x,y) bit will be set if and only if
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* bitmask_overlap(a, b, x - b->w - 1, y - b->h - 1) returns true.
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*
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* Modifies bits o[xoffset ... xoffset + a->w + b->w - 1)
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* [yoffset ... yoffset + a->h + b->h - 1). */
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void bitmask_convolve(const bitmask_t *a, const bitmask_t *b, bitmask_t *o, int xoffset, int yoffset);
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#ifdef __cplusplus
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} /* End of extern "C" { */
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#endif
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#endif
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