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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_
42 #include "c99_compat.h"
45 util_format_srgb_8unorm_to_linear_float_table
[256];
48 util_format_srgb_to_linear_8unorm_table
[256];
51 util_format_linear_to_srgb_8unorm_table
[256];
54 util_format_linear_to_srgb_helper_table
[104];
58 util_format_linear_to_srgb_float(float cl
)
62 else if (cl
< 0.0031308f
)
65 return 1.055f
* powf(cl
, 0.41666f
) - 0.055f
;
72 * Convert a unclamped linear float to srgb value in the [0,255].
75 util_format_linear_float_to_srgb_8unorm(float x
)
78 * This is taken from https://gist.github.com/rygorous/2203834
79 * Use LUT and do linear interpolation.
84 } almostone
, minval
, f
;
85 unsigned tab
, bias
, scale
, t
;
87 almostone
.ui
= 0x3f7fffff;
88 minval
.ui
= (127-13) << 23;
91 * Clamp to [2^(-13), 1-eps]; these two values map to 0 and 1, respectively.
92 * The tests are carefully written so that NaNs map to 0, same as in the
93 * reference implementation.
100 /* Do the table lookup and unpack bias, scale */
102 tab
= util_format_linear_to_srgb_helper_table
[(f
.ui
- minval
.ui
) >> 20];
103 bias
= (tab
>> 16) << 9;
104 scale
= tab
& 0xffff;
106 /* Grab next-highest mantissa bits and perform linear interpolation */
107 t
= (f
.ui
>> 12) & 0xff;
108 return (uint8_t) ((bias
+ scale
*t
) >> 16);
113 * Convert an 8-bit sRGB value from non-linear space to a
114 * linear RGB value in [0, 1].
115 * Implemented with a 256-entry lookup table.
118 util_format_srgb_8unorm_to_linear_float(uint8_t x
)
120 return util_format_srgb_8unorm_to_linear_float_table
[x
];
125 * XXX These 2 functions probably don't make a lot of sense (but lots
126 * of potential callers which most likely all don't make sense neither)
130 * Convert a 8bit normalized value from linear to srgb.
132 static inline uint8_t
133 util_format_linear_to_srgb_8unorm(uint8_t x
)
135 return util_format_linear_to_srgb_8unorm_table
[x
];
140 * Convert a 8bit normalized value from srgb to linear.
142 static inline uint8_t
143 util_format_srgb_to_linear_8unorm(uint8_t x
)
145 return util_format_srgb_to_linear_8unorm_table
[x
];
149 #endif /* U_FORMAT_SRGB_H_ */