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/**************************************************************************
*
* Copyright 2010 VMware, Inc.
* All Rights Reserved.
*
* 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, sub license, 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 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 NON-INFRINGEMENT. IN NO EVENT SHALL
* THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS 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.
*
* The above copyright notice and this permission notice (including the
* next paragraph) shall be included in all copies or substantial portions
* of the Software.
*
**************************************************************************/
/**
* @file
* SRGB translation.
*
* @author Brian Paul <brianp@vmware.com>
* @author Michal Krol <michal@vmware.com>
* @author Jose Fonseca <jfonseca@vmware.com>
*/
#ifndef U_FORMAT_SRGB_H_
#define U_FORMAT_SRGB_H_
#include <stdint.h>
#include <math.h>
extern const float
util_format_srgb_8unorm_to_linear_float_table[256];
extern const uint8_t
util_format_srgb_to_linear_8unorm_table[256];
extern const uint8_t
util_format_linear_to_srgb_8unorm_table[256];
extern const unsigned
util_format_linear_to_srgb_helper_table[104];
static inline float
util_format_linear_to_srgb_float(float cl)
{
if (cl < 0.0f)
return 0.0f;
else if (cl < 0.0031308f)
return 12.92f * cl;
else if (cl < 1.0f)
return 1.055f * powf(cl, 0.41666f) - 0.055f;
else
return 1.0f;
}
/**
* Convert a unclamped linear float to srgb value in the [0,255].
*/
static inline uint8_t
util_format_linear_float_to_srgb_8unorm(float x)
{
/*
* This is taken from https://gist.github.com/rygorous/2203834
* Use LUT and do linear interpolation.
*/
union {
uint32_t ui;
float f;
} almostone, minval, f;
unsigned tab, bias, scale, t;
almostone.ui = 0x3f7fffff;
minval.ui = (127-13) << 23;
/*
* Clamp to [2^(-13), 1-eps]; these two values map to 0 and 1, respectively.
* The tests are carefully written so that NaNs map to 0, same as in the
* reference implementation.
*/
if (!(x > minval.f))
x = minval.f;
if (x > almostone.f)
x = almostone.f;
/* Do the table lookup and unpack bias, scale */
f.f = x;
tab = util_format_linear_to_srgb_helper_table[(f.ui - minval.ui) >> 20];
bias = (tab >> 16) << 9;
scale = tab & 0xffff;
/* Grab next-highest mantissa bits and perform linear interpolation */
t = (f.ui >> 12) & 0xff;
return (uint8_t) ((bias + scale*t) >> 16);
}
/**
* Convert an 8-bit sRGB value from non-linear space to a
* linear RGB value in [0, 1].
* Implemented with a 256-entry lookup table.
*/
static inline float
util_format_srgb_8unorm_to_linear_float(uint8_t x)
{
return util_format_srgb_8unorm_to_linear_float_table[x];
}
/*
* XXX These 2 functions probably don't make a lot of sense (but lots
* of potential callers which most likely all don't make sense neither)
*/
/**
* Convert a 8bit normalized value from linear to srgb.
*/
static inline uint8_t
util_format_linear_to_srgb_8unorm(uint8_t x)
{
return util_format_linear_to_srgb_8unorm_table[x];
}
/**
* Convert a 8bit normalized value from srgb to linear.
*/
static inline uint8_t
util_format_srgb_to_linear_8unorm(uint8_t x)
{
return util_format_srgb_to_linear_8unorm_table[x];
}
#endif /* U_FORMAT_SRGB_H_ */
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