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Implementation of rounds around zero

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The rounds used in the library are towards positive/negative infinity.
Since we're in a cartesian plane, rounds around zero are much more
convenient, so we can use positive and negative values with consistent
results.
This commit is contained in:
Terseus 2014-04-01 13:08:15 +02:00
parent deecd8a137
commit 8739613cfb
1 changed files with 7 additions and 0 deletions
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7
libImaging/Draw.c
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@ -49,6 +49,13 @@
#define BLEND(mask, in1, in2, tmp1, tmp2)\ #define BLEND(mask, in1, in2, tmp1, tmp2)\
(MULDIV255(in1, 255 - mask, tmp1) + MULDIV255(in2, mask, tmp2)) (MULDIV255(in1, 255 - mask, tmp1) + MULDIV255(in2, mask, tmp2))
/*
* Rounds around zero (up=torwards zero, down=away from zero)
* This guarantees that ROUND_UP|DOWN(f) == -ROUND_UP|DOWN(-f)
*/
#define ROUND_UP(f) ((int) ((f) >= 0.0 ? floor((f) + 0.5F) : -floor(fabs(f) + 0.5F)))
#define ROUND_DOWN(f) ((int) ((f) >= 0.0 ? ceil((f) - 0.5F) : -ceil(fabs(f) - 0.5F)))
/* -------------------------------------------------------------------- */ /* -------------------------------------------------------------------- */
/* Primitives */ /* Primitives */
/* -------------------------------------------------------------------- */ /* -------------------------------------------------------------------- */