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
43typedef 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
59typedef 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
76static 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. */
93static INLINE int rgb9e5_FloorLog2(float x)
94{
95   float754 f;
96
97   f.value = x;
98   return (f.field.biasedexponent - 127);
99}
100
101static 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
149static 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