src/gallium/auxiliary/util/u_format_srgb.h

   1 /**************************************************************************
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   3  * Copyright 2010 VMware, Inc.
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  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  * Convert a 8bit normalized value from linear to srgb.
  88  */
  89 static INLINE uint8_t
  90 util_format_linear_to_srgb_8unorm(uint8_t x)
  91 {
  92    return util_format_linear_to_srgb_8unorm_table[x];
  93 }
  94
  95
  96 /**
  97  * Convert a 8bit normalized value from srgb to linear.
  98  */
  99 static INLINE uint8_t
 100 util_format_srgb_to_linear_8unorm(uint8_t x)
 101 {
 102    return util_format_srgb_to_linear_8unorm_table[x];
 103 }
 104
 105
 106 #endif /* U_FORMAT_SRGB_H_ */