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Put the polynomials in horner form to save a multiplication.

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This commit is contained in:
Jorge Rodriguez 2014-07-26 15:36:15 -07:00
parent fb2f8df5cc
commit 6cd81d4dd5
1 changed files with 4 additions and 4 deletions
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8
stb_resample.h
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@ -254,9 +254,9 @@ static float stbr__filter_catmullrom(float x)
float xx = x*x;
if (x < 1.0f)
return 1.5f * (x * xx) - 2.5f * xx + 1;
return 1.5f * xx * (x - 1.66666666f) + 1;
else if (x < 2.0f)
return -0.5f * (x * xx) + 2.5f * xx - 4 * x + 2;
return -0.5f * x * ((xx - 5 * x) + 8) + 2;
return (0.0f);
}
@ -268,9 +268,9 @@ static float stbr__filter_mitchell(float x)
float xx = x*x;
if (x < 1.0f)
return 1.1666666666666f * (x * xx) - 2 * xx + 0.8888888888f;
return 1.1666666666666f * xx * (x - 1.714285715f) + 0.8888888888f;
else if (x < 2.0f)
return -0.3888888888f * (x * xx) + 2 * xx - 3.333333333f * x + 1.777777777777f;
return -0.3888888888f * x * ((xx - 5.14285714f * x) + 8.571428571f) + 1.777777777777f;
return (0.0f);
}