src/mesa/main/rgb9e5.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 /* 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
  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 static INLINE float rgb9e5_MaxOf3(float x, float y, float z)
  91 {
  92    if (x > y) {
  93       return MAX2(x, z);
  94    } else {
  95       return MAX2(y, z);
  96    }
  97 }
  98
  99 /* Ok, FloorLog2 is not correct for the denorm and zero values, but we
 100    are going to do a max of this value with the minimum rgb9e5 exponent
 101    that will hide these problem cases. */
 102 static INLINE int rgb9e5_FloorLog2(float x)
 103 {
 104    float754 f;
 105
 106    f.value = x;
 107    return (f.field.biasedexponent - 127);
 108 }
 109
 110 static INLINE unsigned float3_to_rgb9e5(const float rgb[3])
 111 {
 112    rgb9e5 retval;
 113    float maxrgb;
 114    int rm, gm, bm;
 115    float rc, gc, bc;
 116    int exp_shared, maxm;
 117    double denom;
 118
 119    rc = rgb9e5_ClampRange(rgb[0]);
 120    gc = rgb9e5_ClampRange(rgb[1]);
 121    bc = rgb9e5_ClampRange(rgb[2]);
 122
 123    maxrgb = rgb9e5_MaxOf3(rc, gc, bc);
 124    exp_shared = MAX2(-RGB9E5_EXP_BIAS-1, rgb9e5_FloorLog2(maxrgb)) + 1 + RGB9E5_EXP_BIAS;
 125    assert(exp_shared <= RGB9E5_MAX_VALID_BIASED_EXP);
 126    assert(exp_shared >= 0);
 127    /* This pow function could be replaced by a table. */
 128    denom = pow(2, exp_shared - RGB9E5_EXP_BIAS - RGB9E5_MANTISSA_BITS);
 129
 130    maxm = (int) floor(maxrgb / denom + 0.5);
 131    if (maxm == MAX_RGB9E5_MANTISSA+1) {
 132       denom *= 2;
 133       exp_shared += 1;
 134       assert(exp_shared <= RGB9E5_MAX_VALID_BIASED_EXP);
 135    } else {
 136       assert(maxm <= MAX_RGB9E5_MANTISSA);
 137    }
 138
 139    rm = (int) floor(rc / denom + 0.5);
 140    gm = (int) floor(gc / denom + 0.5);
 141    bm = (int) floor(bc / denom + 0.5);
 142
 143    assert(rm <= MAX_RGB9E5_MANTISSA);
 144    assert(gm <= MAX_RGB9E5_MANTISSA);
 145    assert(bm <= MAX_RGB9E5_MANTISSA);
 146    assert(rm >= 0);
 147    assert(gm >= 0);
 148    assert(bm >= 0);
 149
 150    retval.field.r = rm;
 151    retval.field.g = gm;
 152    retval.field.b = bm;
 153    retval.field.biasedexponent = exp_shared;
 154
 155    return retval.raw;
 156 }
 157
 158 static INLINE void rgb9e5_to_float3(unsigned rgb, float retval[3])
 159 {
 160    rgb9e5 v;
 161    int exponent;
 162    float scale;
 163
 164    v.raw = rgb;
 165    exponent = v.field.biasedexponent - RGB9E5_EXP_BIAS - RGB9E5_MANTISSA_BITS;
 166    scale = (float) pow(2, exponent);
 167
 168    retval[0] = v.field.r * scale;
 169    retval[1] = v.field.g * scale;
 170    retval[2] = v.field.b * scale;
 171 }
 172
 173 #endif