163 lines
4.2 KiB
C
163 lines
4.2 KiB
C
/**************************************************************************
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*
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* Copyright 2010 VMware, Inc.
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* All Rights Reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sub license, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
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* THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
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* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
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* OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
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* USE OR OTHER DEALINGS IN THE SOFTWARE.
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*
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* The above copyright notice and this permission notice (including the
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* next paragraph) shall be included in all copies or substantial portions
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* of the Software.
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*
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**************************************************************************/
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/**
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* @file
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* SRGB translation.
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*
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* @author Brian Paul <brianp@vmware.com>
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* @author Michal Krol <michal@vmware.com>
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* @author Jose Fonseca <jfonseca@vmware.com>
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*/
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#ifndef U_FORMAT_SRGB_H_
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#define U_FORMAT_SRGB_H_
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#include <stdint.h>
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#include <math.h>
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extern const float
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util_format_srgb_8unorm_to_linear_float_table[256];
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extern const uint8_t
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util_format_srgb_to_linear_8unorm_table[256];
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extern const uint8_t
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util_format_linear_to_srgb_8unorm_table[256];
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extern const unsigned
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util_format_linear_to_srgb_helper_table[104];
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static inline float
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util_format_srgb_to_linear_float(float cs)
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{
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if (cs <= 0.0f)
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return 0.0f;
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else if (cs <= 0.04045f)
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return cs / 12.92f;
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else if (cs < 1.0f)
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return powf((cs + 0.055) / 1.055f, 2.4f);
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else
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return 1.0f;
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}
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static inline float
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util_format_linear_to_srgb_float(float cl)
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{
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if (cl <= 0.0f)
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return 0.0f;
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else if (cl < 0.0031308f)
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return 12.92f * cl;
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else if (cl < 1.0f)
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return 1.055f * powf(cl, 0.41666f) - 0.055f;
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else
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return 1.0f;
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}
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/**
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* Convert a unclamped linear float to srgb value in the [0,255].
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*/
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static inline uint8_t
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util_format_linear_float_to_srgb_8unorm(float x)
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{
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/*
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* This is taken from https://gist.github.com/rygorous/2203834
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* Use LUT and do linear interpolation.
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*/
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union {
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uint32_t ui;
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float f;
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} almostone, minval, f;
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unsigned tab, bias, scale, t;
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almostone.ui = 0x3f7fffff;
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minval.ui = (127-13) << 23;
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/*
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* Clamp to [2^(-13), 1-eps]; these two values map to 0 and 1, respectively.
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* The tests are carefully written so that NaNs map to 0, same as in the
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* reference implementation.
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*/
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if (!(x > minval.f))
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x = minval.f;
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if (x > almostone.f)
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x = almostone.f;
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/* Do the table lookup and unpack bias, scale */
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f.f = x;
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tab = util_format_linear_to_srgb_helper_table[(f.ui - minval.ui) >> 20];
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bias = (tab >> 16) << 9;
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scale = tab & 0xffff;
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/* Grab next-highest mantissa bits and perform linear interpolation */
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t = (f.ui >> 12) & 0xff;
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return (uint8_t) ((bias + scale*t) >> 16);
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}
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/**
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* Convert an 8-bit sRGB value from non-linear space to a
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* linear RGB value in [0, 1].
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* Implemented with a 256-entry lookup table.
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*/
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static inline float
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util_format_srgb_8unorm_to_linear_float(uint8_t x)
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{
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return util_format_srgb_8unorm_to_linear_float_table[x];
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}
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/*
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* XXX These 2 functions probably don't make a lot of sense (but lots
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* of potential callers which most likely all don't make sense neither)
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*/
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/**
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* Convert a 8bit normalized value from linear to srgb.
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*/
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static inline uint8_t
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util_format_linear_to_srgb_8unorm(uint8_t x)
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{
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return util_format_linear_to_srgb_8unorm_table[x];
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}
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/**
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* Convert a 8bit normalized value from srgb to linear.
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*/
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static inline uint8_t
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util_format_srgb_to_linear_8unorm(uint8_t x)
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{
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return util_format_srgb_to_linear_8unorm_table[x];
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}
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#endif /* U_FORMAT_SRGB_H_ */
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