src/gallium/auxiliary/util/u_format_r11g11b10f.h

   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 /* 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 #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)
  36
  37 #define UF10_EXPONENT_BIAS   15
  38 #define UF10_EXPONENT_BITS   0x1F
  39 #define UF10_EXPONENT_SHIFT  5
  40 #define UF10_MANTISSA_BITS   0x3F
  41 #define UF10_MANTISSA_SHIFT  (23 - UF10_EXPONENT_SHIFT)
  42 #define UF10_MAX_EXPONENT    (UF10_EXPONENT_BITS << UF10_EXPONENT_SHIFT)
  43
  44 #define F32_INFINITY         0x7f800000
  45
  46 static INLINE unsigned f32_to_uf11(float val)
  47 {
  48    union {
  49       float f;
  50       uint32_t ui;
  51    } f32 = {val};
  52
  53    uint16_t uf11 = 0;
  54
  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;
  60
  61    if (sign) return 0;
  62
  63    if (exponent == 128) { /* Infinity or NaN */
  64       uf11 = UF11_MAX_EXPONENT;
  65       if (mantissa) uf11 |= (mantissa & UF11_MANTISSA_BITS);
  66    }
  67    else if (exponent > 15) { /* Overflow - flush to Infinity */
  68       uf11 = UF11_MAX_EXPONENT;
  69    }
  70    else if (exponent > -15) { /* Representable value */
  71       exponent += UF11_EXPONENT_BIAS;
  72       mantissa >>= UF11_MANTISSA_SHIFT;
  73       uf11 = exponent << UF11_EXPONENT_SHIFT | mantissa;
  74    }
  75
  76    return uf11;
  77 }
  78
  79 static INLINE float uf11_to_f32(uint16_t val)
  80 {
  81    union {
  82       float f;
  83       uint32_t ui;
  84    } f32;
  85
  86    int exponent = (val & 0x07c0) >> UF11_EXPONENT_SHIFT;
  87    int mantissa = (val & 0x003f);
  88
  89    f32.f = 0.0;
  90
  91    if (exponent == 0) {
  92       if (mantissa != 0) {
  93          const float scale = 1.0 / (1 << 20);
  94          f32.f = scale * mantissa;
  95       }
  96    }
  97    else if (exponent == 31) {
  98       f32.ui = F32_INFINITY | mantissa;
  99    }
 100    else {
 101       float scale, decimal;
 102       exponent -= 15;
 103       if (exponent < 0) {
 104          scale = 1.0 / (1 << -exponent);
 105       }
 106       else {
 107          scale = 1 << exponent;
 108       }
 109       decimal = 1.0 + (float) mantissa / 64;
 110       f32.f = scale * decimal;
 111    }
 112
 113    return f32.f;
 114 }
 115
 116 static INLINE unsigned f32_to_uf10(float val)
 117 {
 118    union {
 119       float f;
 120       uint32_t ui;
 121    } f32 = {val};
 122
 123    uint16_t uf10 = 0;
 124
 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;
 130
 131    if (sign) return 0;
 132
 133    if (exponent == 128) { /* Infinity or NaN */
 134       uf10 = UF10_MAX_EXPONENT;
 135       if (mantissa) uf10 |= (mantissa & UF10_MANTISSA_BITS);
 136    }
 137    else if (exponent > 15) { /* Overflow - flush to Infinity */
 138       uf10 = UF10_MAX_EXPONENT;
 139    }
 140    else if (exponent > -15) { /* Representable value */
 141       exponent += UF10_EXPONENT_BIAS;
 142       mantissa >>= UF10_MANTISSA_SHIFT;
 143       uf10 = exponent << UF10_EXPONENT_SHIFT | mantissa;
 144    }
 145
 146    return uf10;
 147 }
 148
 149 static INLINE float uf10_to_f32(uint16_t val)
 150 {
 151    union {
 152       float f;
 153       uint32_t ui;
 154    } f32;
 155
 156    int exponent = (val & 0x07c0) >> UF10_EXPONENT_SHIFT;
 157    int mantissa = (val & 0x003f);
 158
 159    f32.f = 0.0;
 160
 161    if (exponent == 0) {
 162       if (mantissa != 0) {
 163          const float scale = 1.0 / (1 << 20);
 164          f32.f = scale * mantissa;
 165       }
 166    }
 167    else if (exponent == 31) {
 168       f32.ui = F32_INFINITY | mantissa;
 169    }
 170    else {
 171       float scale, decimal;
 172       exponent -= 15;
 173       if (exponent < 0) {
 174          scale = 1.0 / (1 << -exponent);
 175       }
 176       else {
 177          scale = 1 << exponent;
 178       }
 179       decimal = 1.0 + (float) mantissa / 32;
 180       f32.f = scale * decimal;
 181    }
 182
 183    return f32.f;
 184 }
 185
 186 static INLINE unsigned float3_to_r11g11b10f(const float rgb[3])
 187 {
 188    return ( f32_to_uf11(rgb[0]) & 0x7ff) |
 189           ((f32_to_uf11(rgb[1]) & 0x7ff) << 11) |
 190           ((f32_to_uf10(rgb[2]) & 0x3ff) << 22);
 191 }
 192
 193 static INLINE void r11g11b10f_to_float3(unsigned rgb, float retval[3])
 194 {
 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);
 198 }