1 /*
2 * Copyright (C) 2011 Marek Olšák <maraeo@gmail.com>
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
13 * Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
21 * DEALINGS IN THE SOFTWARE.
22 */
23
24 /* Copied from EXT_texture_shared_exponent and edited. */
25
26 #ifndef RGB9E5_H
27 #define RGB9E5_H
28
29 #include <math.h>
30 #include <assert.h>
31
32 #define RGB9E5_EXPONENT_BITS 5
33 #define RGB9E5_MANTISSA_BITS 9
34 #define RGB9E5_EXP_BIAS 15
35 #define RGB9E5_MAX_VALID_BIASED_EXP 31
36
37 #define MAX_RGB9E5_EXP (RGB9E5_MAX_VALID_BIASED_EXP - RGB9E5_EXP_BIAS)
38 #define RGB9E5_MANTISSA_VALUES (1<<RGB9E5_MANTISSA_BITS)
39 #define MAX_RGB9E5_MANTISSA (RGB9E5_MANTISSA_VALUES-1)
40 #define MAX_RGB9E5 (((float)MAX_RGB9E5_MANTISSA)/RGB9E5_MANTISSA_VALUES * (1<<MAX_RGB9E5_EXP))
41 #define EPSILON_RGB9E5 ((1.0/RGB9E5_MANTISSA_VALUES) / (1<<RGB9E5_EXP_BIAS))
42
43 typedef union {
44 unsigned int raw;
45 float value;
46 struct {
47 #if defined(MESA_BIG_ENDIAN) || defined(PIPE_ARCH_BIG_ENDIAN)
48 unsigned int negative:1;
49 unsigned int biasedexponent:8;
50 unsigned int mantissa:23;
51 #else
52 unsigned int mantissa:23;
53 unsigned int biasedexponent:8;
54 unsigned int negative:1;
55 #endif
56 } field;
57 } float754;
58
59 typedef union {
60 unsigned int raw;
61 struct {
62 #if defined(MESA_BIG_ENDIAN) || defined(PIPE_ARCH_BIG_ENDIAN)
63 unsigned int biasedexponent:RGB9E5_EXPONENT_BITS;
64 unsigned int b:RGB9E5_MANTISSA_BITS;
65 unsigned int g:RGB9E5_MANTISSA_BITS;
66 unsigned int r:RGB9E5_MANTISSA_BITS;
67 #else
68 unsigned int r:RGB9E5_MANTISSA_BITS;
69 unsigned int g:RGB9E5_MANTISSA_BITS;
70 unsigned int b:RGB9E5_MANTISSA_BITS;
71 unsigned int biasedexponent:RGB9E5_EXPONENT_BITS;
72 #endif
73 } field;
74 } rgb9e5;
75
rgb9e5_ClampRange(float x)76 static INLINE float rgb9e5_ClampRange(float x)
77 {
78 if (x > 0.0) {
79 if (x >= MAX_RGB9E5) {
80 return MAX_RGB9E5;
81 } else {
82 return x;
83 }
84 } else {
85 /* NaN gets here too since comparisons with NaN always fail! */
86 return 0.0;
87 }
88 }
89
90 /* Ok, FloorLog2 is not correct for the denorm and zero values, but we
91 are going to do a max of this value with the minimum rgb9e5 exponent
92 that will hide these problem cases. */
rgb9e5_FloorLog2(float x)93 static INLINE int rgb9e5_FloorLog2(float x)
94 {
95 float754 f;
96
97 f.value = x;
98 return (f.field.biasedexponent - 127);
99 }
100
float3_to_rgb9e5(const float rgb[3])101 static INLINE unsigned float3_to_rgb9e5(const float rgb[3])
102 {
103 rgb9e5 retval;
104 float maxrgb;
105 int rm, gm, bm;
106 float rc, gc, bc;
107 int exp_shared, maxm;
108 double denom;
109
110 rc = rgb9e5_ClampRange(rgb[0]);
111 gc = rgb9e5_ClampRange(rgb[1]);
112 bc = rgb9e5_ClampRange(rgb[2]);
113
114 maxrgb = MAX3(rc, gc, bc);
115 exp_shared = MAX2(-RGB9E5_EXP_BIAS-1, rgb9e5_FloorLog2(maxrgb)) + 1 + RGB9E5_EXP_BIAS;
116 assert(exp_shared <= RGB9E5_MAX_VALID_BIASED_EXP);
117 assert(exp_shared >= 0);
118 /* This pow function could be replaced by a table. */
119 denom = pow(2, exp_shared - RGB9E5_EXP_BIAS - RGB9E5_MANTISSA_BITS);
120
121 maxm = (int) floor(maxrgb / denom + 0.5);
122 if (maxm == MAX_RGB9E5_MANTISSA+1) {
123 denom *= 2;
124 exp_shared += 1;
125 assert(exp_shared <= RGB9E5_MAX_VALID_BIASED_EXP);
126 } else {
127 assert(maxm <= MAX_RGB9E5_MANTISSA);
128 }
129
130 rm = (int) floor(rc / denom + 0.5);
131 gm = (int) floor(gc / denom + 0.5);
132 bm = (int) floor(bc / denom + 0.5);
133
134 assert(rm <= MAX_RGB9E5_MANTISSA);
135 assert(gm <= MAX_RGB9E5_MANTISSA);
136 assert(bm <= MAX_RGB9E5_MANTISSA);
137 assert(rm >= 0);
138 assert(gm >= 0);
139 assert(bm >= 0);
140
141 retval.field.r = rm;
142 retval.field.g = gm;
143 retval.field.b = bm;
144 retval.field.biasedexponent = exp_shared;
145
146 return retval.raw;
147 }
148
rgb9e5_to_float3(unsigned rgb,float retval[3])149 static INLINE void rgb9e5_to_float3(unsigned rgb, float retval[3])
150 {
151 rgb9e5 v;
152 int exponent;
153 float scale;
154
155 v.raw = rgb;
156 exponent = v.field.biasedexponent - RGB9E5_EXP_BIAS - RGB9E5_MANTISSA_BITS;
157 scale = (float) pow(2, exponent);
158
159 retval[0] = v.field.r * scale;
160 retval[1] = v.field.g * scale;
161 retval[2] = v.field.b * scale;
162 }
163
164 #endif
165