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Diffstat (limited to 'src/util/format_srgb.h')
-rw-r--r-- | src/util/format_srgb.h | 133 |
1 files changed, 133 insertions, 0 deletions
diff --git a/src/util/format_srgb.h b/src/util/format_srgb.h new file mode 100644 index 00000000000..8e92c38f461 --- /dev/null +++ b/src/util/format_srgb.h @@ -0,0 +1,133 @@ +/************************************************************************** + * + * 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 <[email protected]> + * @author Michal Krol <[email protected]> + * @author Jose Fonseca <[email protected]> + */ + +#ifndef U_FORMAT_SRGB_H_ +#define U_FORMAT_SRGB_H_ + +#include <stdint.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]; + + +/** + * 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_ */ |