/************************************************************************** * * 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_srgb_to_linear_float(float cs) { if (cs <= 0.0f) return 0.0f; else if (cs <= 0.04045f) return cs / 12.92f; else if (cs < 1.0f) return powf((cs + 0.055) / 1.055f, 2.4f); else return 1.0f; } 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_ */