GFXprim 2D bitmap graphics library with emphasis on speed and correctness
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gp_fixed_point.h
2/*
3 * Copyright (C) 2009-2012 Cyril Hrubis <metan@ucw.cz>
4 */
5
6/*
7
8 Macros for fixed point arithmetic.
9
10 We use 8 bits for fractional part for coordinates and sizes for Anti Aliased
11 primitives.
12
13 */
14
15#ifndef CORE_GP_FIXED_POINT_H
16#define CORE_GP_FIXED_POINT_H
17
18#include <stdint.h>
19
20/*
21 * Number of bits used for fractional part.
22 */
23#define GP_FP_FRAC_BITS 8
24
25/*
26 * One
27 */
28#define GP_FP_1 (1<<GP_FP_FRAC_BITS)
29
30/*
31 * One Half
32 */
33#define GP_FP_1_2 (1<<(GP_FP_FRAC_BITS - 1))
34
35/*
37 */
39
40/*
42 */
44
45/*
47 */
49
50/*
51 * Substraction.
52 */
53#define GP_FP_SUB(a, b) ((a)-(b))
54
55/*
56 * Multiplication, may overflow.
57 */
58#define GP_FP_MUL(a, b) ((((a) * (b)) + GP_FP_1_2)>>GP_FP_FRAC_BITS)
59
60/*
61 * Division, may overflow
62 */
63#define GP_FP_DIV(a, b) ((((a)<<GP_FP_FRAC_BITS) + GP_FP_1_2) / (b))
64
65/*
66 * Floor.
67 */
69
70/*
71 * Floor with conversion to integer.
72 */
73#define GP_FP_TO_INT(a) ((a)>>GP_FP_FRAC_BITS)
74#define GP_FP_FLOOR_TO_INT(a) GP_FP_TO_INT(a)
75
76/*
77 * Ceiling.
78 */
79#define GP_FP_CEIL(a) (((a) & GP_FP_INT_MASK) + ((a) & GP_FP_FRAC_MASK) ? GP_FP_1 : 0)
80
81/*
82 * Ceilling with conversion to integer.
83 */
84#define GP_FP_CEIL_TO_INT(a) (((a)>>GP_FP_FRAC_BITS) + !!(GP_FP_FRAC(a)))
85
86/*
87 * Rounding.
88 */
89#define GP_FP_ROUND(a) GP_FP_FLOOR((a) + GP_FP_1_2)
90
91/*
92 * Rounding with conversion to integer.
93 */
94#define GP_FP_ROUND_TO_INT(a) ((((a) + GP_FP_1_2))>>GP_FP_FRAC_BITS)
95
96/*
97 * Fractional part.
98 */
100
101/*
102 * Reverse fractional part 1 - frac(x)
103 */
104#define GP_FP_RFRAC(a) (GP_FP_1 - GP_FP_FRAC(a))
105
106/*
107 * Returns an float.
108 */
109#define GP_FP_TO_FLOAT(a) (((float)(a))/((float)GP_FP_1))
110
111/*
112 * Returns fixed point from integer.
113 */
114#define GP_FP_FROM_INT(a) ((a)<<GP_FP_FRAC_BITS)
115
116#endif /* CORE_GP_FIXED_POINT_H */