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  1. /**************************************************************************
  2.  *
  3.  * Copyright 2010 VMware, Inc.
  4.  * All Rights Reserved.
  5.  *
  6.  * Permission is hereby granted, free of charge, to any person obtaining a
  7.  * copy of this software and associated documentation files (the
  8.  * "Software"), to deal in the Software without restriction, including
  9.  * without limitation the rights to use, copy, modify, merge, publish,
  10.  * distribute, sub license, and/or sell copies of the Software, and to
  11.  * permit persons to whom the Software is furnished to do so, subject to
  12.  * the following conditions:
  13.  *
  14.  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  15.  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  16.  * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
  17.  * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
  18.  * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  19.  * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  20.  * USE OR OTHER DEALINGS IN THE SOFTWARE.
  21.  *
  22.  * The above copyright notice and this permission notice (including the
  23.  * next paragraph) shall be included in all copies or substantial portions
  24.  * of the Software.
  25.  *
  26.  **************************************************************************/
  27.  
  28. /**
  29.  * @file
  30.  * SRGB translation.
  31.  *
  32.  * @author Brian Paul <brianp@vmware.com>
  33.  * @author Michal Krol <michal@vmware.com>
  34.  * @author Jose Fonseca <jfonseca@vmware.com>
  35.  */
  36.  
  37. #ifndef U_FORMAT_SRGB_H_
  38. #define U_FORMAT_SRGB_H_
  39.  
  40.  
  41. #include "pipe/p_compiler.h"
  42. #include "u_math.h"
  43.  
  44.  
  45. extern const float
  46. util_format_srgb_8unorm_to_linear_float_table[256];
  47.  
  48. extern const uint8_t
  49. util_format_srgb_to_linear_8unorm_table[256];
  50.  
  51. extern const uint8_t
  52. util_format_linear_to_srgb_8unorm_table[256];
  53.  
  54.  
  55. /**
  56.  * Convert a unclamped linear float to srgb value in the [0,255].
  57.  * XXX this hasn't been tested (render to srgb surface).
  58.  * XXX this needs optimization.
  59.  */
  60. static INLINE uint8_t
  61. util_format_linear_float_to_srgb_8unorm(float x)
  62. {
  63.    if (x >= 1.0f)
  64.       return 255;
  65.    else if (x >= 0.0031308f)
  66.       return float_to_ubyte(1.055f * powf(x, 0.41666f) - 0.055f);
  67.    else if (x > 0.0f)
  68.       return float_to_ubyte(12.92f * x);
  69.    else
  70.       return 0;
  71. }
  72.  
  73.  
  74. /**
  75.  * Convert an 8-bit sRGB value from non-linear space to a
  76.  * linear RGB value in [0, 1].
  77.  * Implemented with a 256-entry lookup table.
  78.  */
  79. static INLINE float
  80. util_format_srgb_8unorm_to_linear_float(uint8_t x)
  81. {
  82.    return util_format_srgb_8unorm_to_linear_float_table[x];
  83. }
  84.  
  85.  
  86. /*
  87.  * XXX These 2 functions probably don't make a lot of sense (but lots
  88.  * of potential callers which most likely all don't make sense neither)
  89.  */
  90.  
  91. /**
  92.  * Convert a 8bit normalized value from linear to srgb.
  93.  */
  94. static INLINE uint8_t
  95. util_format_linear_to_srgb_8unorm(uint8_t x)
  96. {
  97.    return util_format_linear_to_srgb_8unorm_table[x];
  98. }
  99.  
  100.  
  101. /**
  102.  * Convert a 8bit normalized value from srgb to linear.
  103.  */
  104. static INLINE uint8_t
  105. util_format_srgb_to_linear_8unorm(uint8_t x)
  106. {
  107.    return util_format_srgb_to_linear_8unorm_table[x];
  108. }
  109.  
  110.  
  111. #endif /* U_FORMAT_SRGB_H_ */
  112.