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3719602c PC |
1 | /* Copyright (C) 2010-2020 The RetroArch team |
2 | * | |
3 | * --------------------------------------------------------------------------------------- | |
4 | * The following license statement only applies to this file (filters.h). | |
5 | * --------------------------------------------------------------------------------------- | |
6 | * | |
7 | * Permission is hereby granted, free of charge, | |
8 | * to any person obtaining a copy of this software and associated documentation files (the "Software"), | |
9 | * to deal in the Software without restriction, including without limitation the rights to | |
10 | * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, | |
11 | * and to permit persons to whom the Software is furnished to do so, subject to the following conditions: | |
12 | * | |
13 | * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. | |
14 | * | |
15 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, | |
16 | * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | |
17 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. | |
18 | * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, | |
19 | * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | |
20 | * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. | |
21 | */ | |
22 | ||
23 | #ifndef _LIBRETRO_SDK_FILTERS_H | |
24 | #define _LIBRETRO_SDK_FILTERS_H | |
25 | ||
26 | /* for MSVC; should be benign under any circumstances */ | |
27 | #define _USE_MATH_DEFINES | |
28 | ||
29 | #include <stdlib.h> | |
30 | #include <math.h> | |
31 | #include <retro_inline.h> | |
32 | #include <retro_math.h> | |
33 | ||
34 | /** | |
35 | * sinc: | |
36 | * | |
37 | * Pure function. | |
38 | **/ | |
39 | static INLINE double sinc(double val) | |
40 | { | |
41 | if (fabs(val) < 0.00001) | |
42 | return 1.0; | |
43 | return sin(val) / val; | |
44 | } | |
45 | ||
46 | /** | |
47 | * paeth: | |
48 | * | |
49 | * Pure function. | |
50 | * Paeth prediction filter. | |
51 | **/ | |
52 | static INLINE int paeth(int a, int b, int c) | |
53 | { | |
54 | int p = a + b - c; | |
55 | int pa = abs(p - a); | |
56 | int pb = abs(p - b); | |
57 | int pc = abs(p - c); | |
58 | ||
59 | if (pa <= pb && pa <= pc) | |
60 | return a; | |
61 | else if (pb <= pc) | |
62 | return b; | |
63 | return c; | |
64 | } | |
65 | ||
66 | /** | |
67 | * besseli0: | |
68 | * | |
69 | * Pure function. | |
70 | * | |
71 | * Modified Bessel function of first order. | |
72 | * Check Wiki for mathematical definition ... | |
73 | **/ | |
74 | static INLINE double besseli0(double x) | |
75 | { | |
76 | int i; | |
77 | double sum = 0.0; | |
78 | double factorial = 1.0; | |
79 | double factorial_mult = 0.0; | |
80 | double x_pow = 1.0; | |
81 | double two_div_pow = 1.0; | |
82 | double x_sqr = x * x; | |
83 | ||
84 | /* Approximate. This is an infinite sum. | |
85 | * Luckily, it converges rather fast. */ | |
86 | for (i = 0; i < 18; i++) | |
87 | { | |
88 | sum += x_pow * two_div_pow / (factorial * factorial); | |
89 | factorial_mult += 1.0; | |
90 | x_pow *= x_sqr; | |
91 | two_div_pow *= 0.25; | |
92 | factorial *= factorial_mult; | |
93 | } | |
94 | ||
95 | return sum; | |
96 | } | |
97 | ||
98 | static INLINE double kaiser_window_function(double index, double beta) | |
99 | { | |
100 | return besseli0(beta * sqrtf(1 - index * index)); | |
101 | } | |
102 | ||
103 | #endif |