1 /* 2 * Copyright (C) 2011 Marek Olk <maraeo (at) 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 /* 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 27 * below. 28 */ 29 30 #include <stdint.h> 31 32 #define UF11(e, m) ((e << 6) | (m)) 33 #define UF11_EXPONENT_BIAS 15 34 #define UF11_EXPONENT_BITS 0x1F 35 #define UF11_EXPONENT_SHIFT 6 36 #define UF11_MANTISSA_BITS 0x3F 37 #define UF11_MANTISSA_SHIFT (23 - UF11_EXPONENT_SHIFT) 38 #define UF11_MAX_EXPONENT (UF11_EXPONENT_BITS << UF11_EXPONENT_SHIFT) 39 40 #define UF10(e, m) ((e << 5) | (m)) 41 #define UF10_EXPONENT_BIAS 15 42 #define UF10_EXPONENT_BITS 0x1F 43 #define UF10_EXPONENT_SHIFT 5 44 #define UF10_MANTISSA_BITS 0x1F 45 #define UF10_MANTISSA_SHIFT (23 - UF10_EXPONENT_SHIFT) 46 #define UF10_MAX_EXPONENT (UF10_EXPONENT_BITS << UF10_EXPONENT_SHIFT) 47 48 #define F32_INFINITY 0x7f800000 49 50 static inline uint32_t f32_to_uf11(float val) 51 { 52 union { 53 float f; 54 uint32_t ui; 55 } f32 = {val}; 56 57 uint16_t uf11 = 0; 58 59 /* Decode little-endian 32-bit floating-point value */ 60 int sign = (f32.ui >> 16) & 0x8000; 61 /* Map exponent to the range [-127,128] */ 62 int exponent = ((f32.ui >> 23) & 0xff) - 127; 63 int mantissa = f32.ui & 0x007fffff; 64 65 if (exponent == 128) { /* Infinity or NaN */ 66 /* From the GL_EXT_packed_float spec: 67 * 68 * "Additionally: negative infinity is converted to zero; positive 69 * infinity is converted to positive infinity; and both positive and 70 * negative NaN are converted to positive NaN." 71 */ 72 uf11 = UF11_MAX_EXPONENT; 73 if (mantissa) { 74 uf11 |= 1; /* NaN */ 75 } else { 76 if (sign) 77 uf11 = 0; /* 0.0 */ 78 } 79 } else if (sign) { 80 return 0; 81 } else if (val > 65024.0f) { 82 /* From the GL_EXT_packed_float spec: 83 * 84 * "Likewise, finite positive values greater than 65024 (the maximum 85 * finite representable unsigned 11-bit floating-point value) are 86 * converted to 65024." 87 */ 88 uf11 = UF11(30, 63); 89 } else if (exponent > -15) { /* Representable value */ 90 exponent += UF11_EXPONENT_BIAS; 91 mantissa >>= UF11_MANTISSA_SHIFT; 92 uf11 = exponent << UF11_EXPONENT_SHIFT | mantissa; 93 } 94 95 return uf11; 96 } 97 98 static inline float uf11_to_f32(uint16_t val) 99 { 100 union { 101 float f; 102 uint32_t ui; 103 } f32; 104 105 int exponent = (val & 0x07c0) >> UF11_EXPONENT_SHIFT; 106 int mantissa = (val & 0x003f); 107 108 f32.f = 0.0; 109 110 if (exponent == 0) { 111 if (mantissa != 0) { 112 const float scale = 1.0 / (1 << 20); 113 f32.f = scale * mantissa; 114 } 115 } else if (exponent == 31) { 116 f32.ui = F32_INFINITY | mantissa; 117 } else { 118 float scale, decimal; 119 exponent -= 15; 120 if (exponent < 0) { 121 scale = 1.0f / (1 << -exponent); 122 } else { 123 scale = (float) (1 << exponent); 124 } 125 decimal = 1.0f + (float) mantissa / 64; 126 f32.f = scale * decimal; 127 } 128 129 return f32.f; 130 } 131 132 static inline uint32_t f32_to_uf10(float val) 133 { 134 union { 135 float f; 136 uint32_t ui; 137 } f32 = {val}; 138 139 uint16_t uf10 = 0; 140 141 /* Decode little-endian 32-bit floating-point value */ 142 int sign = (f32.ui >> 16) & 0x8000; 143 /* Map exponent to the range [-127,128] */ 144 int exponent = ((f32.ui >> 23) & 0xff) - 127; 145 int mantissa = f32.ui & 0x007fffff; 146 147 if (exponent == 128) { 148 /* From the GL_EXT_packed_float spec: 149 * 150 * "Additionally: negative infinity is converted to zero; positive 151 * infinity is converted to positive infinity; and both positive and 152 * negative NaN are converted to positive NaN." 153 */ 154 uf10 = UF10_MAX_EXPONENT; 155 if (mantissa) { 156 uf10 |= 1; /* NaN */ 157 } else { 158 if (sign) 159 uf10 = 0; /* 0.0 */ 160 } 161 } else if (sign) { 162 return 0; 163 } else if (val > 64512.0f) { 164 /* From the GL_EXT_packed_float spec: 165 * 166 * "Likewise, finite positive values greater than 64512 (the maximum 167 * finite representable unsigned 10-bit floating-point value) are 168 * converted to 64512." 169 */ 170 uf10 = UF10(30, 31); 171 } else if (exponent > -15) { /* Representable value */ 172 exponent += UF10_EXPONENT_BIAS; 173 mantissa >>= UF10_MANTISSA_SHIFT; 174 uf10 = exponent << UF10_EXPONENT_SHIFT | mantissa; 175 } 176 177 return uf10; 178 } 179 180 static inline float uf10_to_f32(uint16_t val) 181 { 182 union { 183 float f; 184 uint32_t ui; 185 } f32; 186 187 int exponent = (val & 0x03e0) >> UF10_EXPONENT_SHIFT; 188 int mantissa = (val & 0x001f); 189 190 f32.f = 0.0; 191 192 if (exponent == 0) { 193 if (mantissa != 0) { 194 const float scale = 1.0 / (1 << 19); 195 f32.f = scale * mantissa; 196 } 197 } else if (exponent == 31) { 198 f32.ui = F32_INFINITY | mantissa; 199 } else { 200 float scale, decimal; 201 exponent -= 15; 202 if (exponent < 0) { 203 scale = 1.0f / (1 << -exponent); 204 } 205 else { 206 scale = (float) (1 << exponent); 207 } 208 decimal = 1.0f + (float) mantissa / 32; 209 f32.f = scale * decimal; 210 } 211 212 return f32.f; 213 } 214 215 static inline uint32_t float3_to_r11g11b10f(const float rgb[3]) 216 { 217 return ( f32_to_uf11(rgb[0]) & 0x7ff) | 218 ((f32_to_uf11(rgb[1]) & 0x7ff) << 11) | 219 ((f32_to_uf10(rgb[2]) & 0x3ff) << 22); 220 } 221 222 static inline void r11g11b10f_to_float3(uint32_t rgb, float retval[3]) 223 { 224 retval[0] = uf11_to_f32( rgb & 0x7ff); 225 retval[1] = uf11_to_f32((rgb >> 11) & 0x7ff); 226 retval[2] = uf10_to_f32((rgb >> 22) & 0x3ff); 227 } 228
