/*
* Copyright (C) 2011 Marek Olšák <maraeo@gmail.com>
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
/* Copied from EXT_texture_shared_exponent and edited. */
#ifndef RGB9E5_H
#define RGB9E5_H
#include <math.h>
#include <assert.h>
#define RGB9E5_EXPONENT_BITS 5
#define RGB9E5_MANTISSA_BITS 9
#define RGB9E5_EXP_BIAS 15
#define RGB9E5_MAX_VALID_BIASED_EXP 31
#define MAX_RGB9E5_EXP (RGB9E5_MAX_VALID_BIASED_EXP - RGB9E5_EXP_BIAS)
#define RGB9E5_MANTISSA_VALUES (1<<RGB9E5_MANTISSA_BITS)
#define MAX_RGB9E5_MANTISSA (RGB9E5_MANTISSA_VALUES-1)
#define MAX_RGB9E5 (((float)MAX_RGB9E5_MANTISSA)/RGB9E5_MANTISSA_VALUES * (1<<MAX_RGB9E5_EXP))
#define EPSILON_RGB9E5 ((1.0/RGB9E5_MANTISSA_VALUES) / (1<<RGB9E5_EXP_BIAS))
typedef union {
unsigned int raw;
float value;
struct {
#if defined(MESA_BIG_ENDIAN) || defined(PIPE_ARCH_BIG_ENDIAN)
unsigned int negative:1;
unsigned int biasedexponent:8;
unsigned int mantissa:23;
#else
unsigned int mantissa:23;
unsigned int biasedexponent:8;
unsigned int negative:1;
#endif
} field;
} float754;
typedef union {
unsigned int raw;
struct {
#if defined(MESA_BIG_ENDIAN) || defined(PIPE_ARCH_BIG_ENDIAN)
unsigned int biasedexponent:RGB9E5_EXPONENT_BITS;
unsigned int b:RGB9E5_MANTISSA_BITS;
unsigned int g:RGB9E5_MANTISSA_BITS;
unsigned int r:RGB9E5_MANTISSA_BITS;
#else
unsigned int r:RGB9E5_MANTISSA_BITS;
unsigned int g:RGB9E5_MANTISSA_BITS;
unsigned int b:RGB9E5_MANTISSA_BITS;
unsigned int biasedexponent:RGB9E5_EXPONENT_BITS;
#endif
} field;
} rgb9e5;
static INLINE float rgb9e5_ClampRange(float x)
{
if (x > 0.0) {
if (x >= MAX_RGB9E5) {
return MAX_RGB9E5;
} else {
return x;
}
} else {
/* NaN gets here too since comparisons with NaN always fail! */
return 0.0;
}
}
/* Ok, FloorLog2 is not correct for the denorm and zero values, but we
are going to do a max of this value with the minimum rgb9e5 exponent
that will hide these problem cases. */
static INLINE int rgb9e5_FloorLog2(float x)
{
float754 f;
f.value = x;
return (f.field.biasedexponent - 127);
}
static INLINE unsigned float3_to_rgb9e5(const float rgb[3])
{
rgb9e5 retval;
float maxrgb;
int rm, gm, bm;
float rc, gc, bc;
int exp_shared, maxm;
double denom;
rc = rgb9e5_ClampRange(rgb[0]);
gc = rgb9e5_ClampRange(rgb[1]);
bc = rgb9e5_ClampRange(rgb[2]);
maxrgb = MAX3(rc, gc, bc);
exp_shared = MAX2(-RGB9E5_EXP_BIAS-1, rgb9e5_FloorLog2(maxrgb)) + 1 + RGB9E5_EXP_BIAS;
assert(exp_shared <= RGB9E5_MAX_VALID_BIASED_EXP);
assert(exp_shared >= 0);
/* This pow function could be replaced by a table. */
denom = pow(2, exp_shared - RGB9E5_EXP_BIAS - RGB9E5_MANTISSA_BITS);
maxm = (int) floor(maxrgb / denom + 0.5);
if (maxm == MAX_RGB9E5_MANTISSA+1) {
denom *= 2;
exp_shared += 1;
assert(exp_shared <= RGB9E5_MAX_VALID_BIASED_EXP);
} else {
assert(maxm <= MAX_RGB9E5_MANTISSA);
}
rm = (int) floor(rc / denom + 0.5);
gm = (int) floor(gc / denom + 0.5);
bm = (int) floor(bc / denom + 0.5);
assert(rm <= MAX_RGB9E5_MANTISSA);
assert(gm <= MAX_RGB9E5_MANTISSA);
assert(bm <= MAX_RGB9E5_MANTISSA);
assert(rm >= 0);
assert(gm >= 0);
assert(bm >= 0);
retval.field.r = rm;
retval.field.g = gm;
retval.field.b = bm;
retval.field.biasedexponent = exp_shared;
return retval.raw;
}
static INLINE void rgb9e5_to_float3(unsigned rgb, float retval[3])
{
rgb9e5 v;
int exponent;
float scale;
v.raw = rgb;
exponent = v.field.biasedexponent - RGB9E5_EXP_BIAS - RGB9E5_MANTISSA_BITS;
scale = (float) pow(2, exponent);
retval[0] = v.field.r * scale;
retval[1] = v.field.g * scale;
retval[2] = v.field.b * scale;
}
#endif