2 * Copyright (C) 2011 Marek Olšák <maraeo@gmail.com>
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
21 * DEALINGS IN THE SOFTWARE.
24 /* Copied from EXT_texture_shared_exponent and edited, getting rid of
25 * expensive float math bits too. */
34 #define RGB9E5_EXPONENT_BITS 5
35 #define RGB9E5_MANTISSA_BITS 9
36 #define RGB9E5_EXP_BIAS 15
37 #define RGB9E5_MAX_VALID_BIASED_EXP 31
39 #define MAX_RGB9E5_EXP (RGB9E5_MAX_VALID_BIASED_EXP - RGB9E5_EXP_BIAS)
40 #define RGB9E5_MANTISSA_VALUES (1<<RGB9E5_MANTISSA_BITS)
41 #define MAX_RGB9E5_MANTISSA (RGB9E5_MANTISSA_VALUES-1)
42 #define MAX_RGB9E5 (((float)MAX_RGB9E5_MANTISSA)/RGB9E5_MANTISSA_VALUES * (1<<MAX_RGB9E5_EXP))
48 #if defined(MESA_BIG_ENDIAN) || defined(PIPE_ARCH_BIG_ENDIAN)
49 unsigned int negative
:1;
50 unsigned int biasedexponent
:8;
51 unsigned int mantissa
:23;
53 unsigned int mantissa
:23;
54 unsigned int biasedexponent
:8;
55 unsigned int negative
:1;
63 #if defined(MESA_BIG_ENDIAN) || defined(PIPE_ARCH_BIG_ENDIAN)
64 unsigned int biasedexponent
:RGB9E5_EXPONENT_BITS
;
65 unsigned int b
:RGB9E5_MANTISSA_BITS
;
66 unsigned int g
:RGB9E5_MANTISSA_BITS
;
67 unsigned int r
:RGB9E5_MANTISSA_BITS
;
69 unsigned int r
:RGB9E5_MANTISSA_BITS
;
70 unsigned int g
:RGB9E5_MANTISSA_BITS
;
71 unsigned int b
:RGB9E5_MANTISSA_BITS
;
72 unsigned int biasedexponent
:RGB9E5_EXPONENT_BITS
;
78 static inline int rgb9e5_ClampRange(float x
)
83 max
.value
= MAX_RGB9E5
;
85 if (f
.raw
> 0x7f800000)
86 /* catches neg, NaNs */
88 else if (f
.raw
>= max
.raw
)
94 static inline unsigned float3_to_rgb9e5(const float rgb
[3])
97 int rm
, gm
, bm
, exp_shared
;
98 float754 revdenom
= {0};
99 float754 rc
, bc
, gc
, maxrgb
;
101 rc
.raw
= rgb9e5_ClampRange(rgb
[0]);
102 gc
.raw
= rgb9e5_ClampRange(rgb
[1]);
103 bc
.raw
= rgb9e5_ClampRange(rgb
[2]);
104 maxrgb
.raw
= MAX3(rc
.raw
, gc
.raw
, bc
.raw
);
107 * Compared to what the spec suggests, instead of conditionally adjusting
108 * the exponent after the fact do it here by doing the equivalent of +0.5 -
109 * the int add will spill over into the exponent in this case.
111 maxrgb
.raw
+= maxrgb
.raw
& (1 << (23-9));
112 exp_shared
= MAX2((maxrgb
.raw
>> 23), -RGB9E5_EXP_BIAS
- 1 + 127) +
113 1 + RGB9E5_EXP_BIAS
- 127;
114 revdenom
.field
.biasedexponent
= 127 - (exp_shared
- RGB9E5_EXP_BIAS
-
115 RGB9E5_MANTISSA_BITS
) + 1;
116 assert(exp_shared
<= RGB9E5_MAX_VALID_BIASED_EXP
);
119 * The spec uses strict round-up behavior (d3d10 disagrees, but in any case
120 * must match what is done above for figuring out exponent).
121 * We avoid the doubles ((int) rc * revdenom + 0.5) by doing the rounding
122 * ourselves (revdenom was adjusted by +1, above).
124 rm
= (int) (rc
.value
* revdenom
.value
);
125 gm
= (int) (gc
.value
* revdenom
.value
);
126 bm
= (int) (bc
.value
* revdenom
.value
);
127 rm
= (rm
& 1) + (rm
>> 1);
128 gm
= (gm
& 1) + (gm
>> 1);
129 bm
= (bm
& 1) + (bm
>> 1);
131 assert(rm
<= MAX_RGB9E5_MANTISSA
);
132 assert(gm
<= MAX_RGB9E5_MANTISSA
);
133 assert(bm
<= MAX_RGB9E5_MANTISSA
);
141 retval
.field
.biasedexponent
= exp_shared
;
146 static inline void rgb9e5_to_float3(unsigned rgb
, float retval
[3])
150 float754 scale
= {0};
153 exponent
= v
.field
.biasedexponent
- RGB9E5_EXP_BIAS
- RGB9E5_MANTISSA_BITS
;
154 scale
.field
.biasedexponent
= exponent
+ 127;
156 retval
[0] = v
.field
.r
* scale
.value
;
157 retval
[1] = v
.field
.g
* scale
.value
;
158 retval
[2] = v
.field
.b
* scale
.value
;