0,0 → 1,149 |
/************************************************************************** |
* |
* 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> |
#include "c99_compat.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_ */ |