2 * Copyright (C) 2011 Marek Olšák <maraeo@gmail.com>
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:
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
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.
24 /* Based on code from The OpenGL Programming Guide / 7th Edition, Appendix J.
25 * Available here: http://www.opengl-redbook.com/appendices/
26 * The algorithm in the book contains a bug though, which is fixed in the code
30 #define UF11_EXPONENT_BIAS 15
31 #define UF11_EXPONENT_BITS 0x1F
32 #define UF11_EXPONENT_SHIFT 6
33 #define UF11_MANTISSA_BITS 0x3F
34 #define UF11_MANTISSA_SHIFT (23 - UF11_EXPONENT_SHIFT)
35 #define UF11_MAX_EXPONENT (UF11_EXPONENT_BITS << UF11_EXPONENT_SHIFT)
37 #define UF10_EXPONENT_BIAS 15
38 #define UF10_EXPONENT_BITS 0x1F
39 #define UF10_EXPONENT_SHIFT 5
40 #define UF10_MANTISSA_BITS 0x1F
41 #define UF10_MANTISSA_SHIFT (23 - UF10_EXPONENT_SHIFT)
42 #define UF10_MAX_EXPONENT (UF10_EXPONENT_BITS << UF10_EXPONENT_SHIFT)
44 #define F32_INFINITY 0x7f800000
46 static INLINE unsigned f32_to_uf11(float val)
55 /* Decode little-endian 32-bit floating-point value */
56 int sign = (f32.ui >> 16) & 0x8000;
57 /* Map exponent to the range [-127,128] */
58 int exponent = ((f32.ui >> 23) & 0xff) - 127;
59 int mantissa = f32.ui & 0x007fffff;
63 if (exponent == 128) { /* Infinity or NaN */
64 uf11 = UF11_MAX_EXPONENT;
65 if (mantissa) uf11 |= (mantissa & UF11_MANTISSA_BITS);
67 else if (exponent > 15) { /* Overflow - flush to Infinity */
68 uf11 = UF11_MAX_EXPONENT;
70 else if (exponent > -15) { /* Representable value */
71 exponent += UF11_EXPONENT_BIAS;
72 mantissa >>= UF11_MANTISSA_SHIFT;
73 uf11 = exponent << UF11_EXPONENT_SHIFT | mantissa;
79 static INLINE float uf11_to_f32(uint16_t val)
86 int exponent = (val & 0x07c0) >> UF11_EXPONENT_SHIFT;
87 int mantissa = (val & 0x003f);
93 const float scale = 1.0 / (1 << 20);
94 f32.f = scale * mantissa;
97 else if (exponent == 31) {
98 f32.ui = F32_INFINITY | mantissa;
101 float scale, decimal;
104 scale = 1.0 / (1 << -exponent);
107 scale = 1 << exponent;
109 decimal = 1.0 + (float) mantissa / 64;
110 f32.f = scale * decimal;
116 static INLINE unsigned f32_to_uf10(float val)
125 /* Decode little-endian 32-bit floating-point value */
126 int sign = (f32.ui >> 16) & 0x8000;
127 /* Map exponent to the range [-127,128] */
128 int exponent = ((f32.ui >> 23) & 0xff) - 127;
129 int mantissa = f32.ui & 0x007fffff;
133 if (exponent == 128) { /* Infinity or NaN */
134 uf10 = UF10_MAX_EXPONENT;
135 if (mantissa) uf10 |= (mantissa & UF10_MANTISSA_BITS);
137 else if (exponent > 15) { /* Overflow - flush to Infinity */
138 uf10 = UF10_MAX_EXPONENT;
140 else if (exponent > -15) { /* Representable value */
141 exponent += UF10_EXPONENT_BIAS;
142 mantissa >>= UF10_MANTISSA_SHIFT;
143 uf10 = exponent << UF10_EXPONENT_SHIFT | mantissa;
149 static INLINE float uf10_to_f32(uint16_t val)
156 int exponent = (val & 0x03e0) >> UF10_EXPONENT_SHIFT;
157 int mantissa = (val & 0x001f);
163 const float scale = 1.0 / (1 << 20);
164 f32.f = scale * mantissa;
167 else if (exponent == 31) {
168 f32.ui = F32_INFINITY | mantissa;
171 float scale, decimal;
174 scale = 1.0 / (1 << -exponent);
177 scale = 1 << exponent;
179 decimal = 1.0 + (float) mantissa / 32;
180 f32.f = scale * decimal;
186 static INLINE unsigned float3_to_r11g11b10f(const float rgb[3])
188 return ( f32_to_uf11(rgb[0]) & 0x7ff) |
189 ((f32_to_uf11(rgb[1]) & 0x7ff) << 11) |
190 ((f32_to_uf10(rgb[2]) & 0x3ff) << 22);
193 static INLINE void r11g11b10f_to_float3(unsigned rgb, float retval[3])
195 retval[0] = uf11_to_f32( rgb & 0x7ff);
196 retval[1] = uf11_to_f32((rgb >> 11) & 0x7ff);
197 retval[2] = uf10_to_f32((rgb >> 22) & 0x3ff);