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32 * @author Brian Paul <brianp@vmware.com>
33 * @author Michal Krol <michal@vmware.com>
34 * @author Jose Fonseca <jfonseca@vmware.com>
37 #ifndef U_FORMAT_SRGB_H_
38 #define U_FORMAT_SRGB_H_
43 util_format_srgb_8unorm_to_linear_float_table
[256];
46 util_format_srgb_to_linear_8unorm_table
[256];
49 util_format_linear_to_srgb_8unorm_table
[256];
52 util_format_linear_to_srgb_helper_table
[104];
56 * Convert a unclamped linear float to srgb value in the [0,255].
59 util_format_linear_float_to_srgb_8unorm(float x
)
62 * This is taken from https://gist.github.com/rygorous/2203834
63 * Use LUT and do linear interpolation.
68 } almostone
, minval
, f
;
69 unsigned tab
, bias
, scale
, t
;
71 almostone
.ui
= 0x3f7fffff;
72 minval
.ui
= (127-13) << 23;
75 * Clamp to [2^(-13), 1-eps]; these two values map to 0 and 1, respectively.
76 * The tests are carefully written so that NaNs map to 0, same as in the
77 * reference implementation.
84 /* Do the table lookup and unpack bias, scale */
86 tab
= util_format_linear_to_srgb_helper_table
[(f
.ui
- minval
.ui
) >> 20];
87 bias
= (tab
>> 16) << 9;
90 /* Grab next-highest mantissa bits and perform linear interpolation */
91 t
= (f
.ui
>> 12) & 0xff;
92 return (uint8_t) ((bias
+ scale
*t
) >> 16);
97 * Convert an 8-bit sRGB value from non-linear space to a
98 * linear RGB value in [0, 1].
99 * Implemented with a 256-entry lookup table.
102 util_format_srgb_8unorm_to_linear_float(uint8_t x
)
104 return util_format_srgb_8unorm_to_linear_float_table
[x
];
109 * XXX These 2 functions probably don't make a lot of sense (but lots
110 * of potential callers which most likely all don't make sense neither)
114 * Convert a 8bit normalized value from linear to srgb.
116 static inline uint8_t
117 util_format_linear_to_srgb_8unorm(uint8_t x
)
119 return util_format_linear_to_srgb_8unorm_table
[x
];
124 * Convert a 8bit normalized value from srgb to linear.
126 static inline uint8_t
127 util_format_srgb_to_linear_8unorm(uint8_t x
)
129 return util_format_srgb_to_linear_8unorm_table
[x
];
133 #endif /* U_FORMAT_SRGB_H_ */