xref: /aosp_15_r20/external/angle/src/common/mathutil.cpp (revision 8975f5c5ed3d1c378011245431ada316dfb6f244)
1*8975f5c5SAndroid Build Coastguard Worker //
2*8975f5c5SAndroid Build Coastguard Worker // Copyright 2013 The ANGLE Project Authors. All rights reserved.
3*8975f5c5SAndroid Build Coastguard Worker // Use of this source code is governed by a BSD-style license that can be
4*8975f5c5SAndroid Build Coastguard Worker // found in the LICENSE file.
5*8975f5c5SAndroid Build Coastguard Worker //
6*8975f5c5SAndroid Build Coastguard Worker 
7*8975f5c5SAndroid Build Coastguard Worker // mathutil.cpp: Math and bit manipulation functions.
8*8975f5c5SAndroid Build Coastguard Worker 
9*8975f5c5SAndroid Build Coastguard Worker #include "common/mathutil.h"
10*8975f5c5SAndroid Build Coastguard Worker 
11*8975f5c5SAndroid Build Coastguard Worker #include <math.h>
12*8975f5c5SAndroid Build Coastguard Worker #include <algorithm>
13*8975f5c5SAndroid Build Coastguard Worker 
14*8975f5c5SAndroid Build Coastguard Worker namespace gl
15*8975f5c5SAndroid Build Coastguard Worker {
16*8975f5c5SAndroid Build Coastguard Worker 
17*8975f5c5SAndroid Build Coastguard Worker namespace
18*8975f5c5SAndroid Build Coastguard Worker {
19*8975f5c5SAndroid Build Coastguard Worker 
20*8975f5c5SAndroid Build Coastguard Worker struct RGB9E5Data
21*8975f5c5SAndroid Build Coastguard Worker {
22*8975f5c5SAndroid Build Coastguard Worker     unsigned int R : 9;
23*8975f5c5SAndroid Build Coastguard Worker     unsigned int G : 9;
24*8975f5c5SAndroid Build Coastguard Worker     unsigned int B : 9;
25*8975f5c5SAndroid Build Coastguard Worker     unsigned int E : 5;
26*8975f5c5SAndroid Build Coastguard Worker };
27*8975f5c5SAndroid Build Coastguard Worker 
28*8975f5c5SAndroid Build Coastguard Worker // B is the exponent bias (15)
29*8975f5c5SAndroid Build Coastguard Worker constexpr int g_sharedexp_bias = 15;
30*8975f5c5SAndroid Build Coastguard Worker 
31*8975f5c5SAndroid Build Coastguard Worker // N is the number of mantissa bits per component (9)
32*8975f5c5SAndroid Build Coastguard Worker constexpr int g_sharedexp_mantissabits = 9;
33*8975f5c5SAndroid Build Coastguard Worker 
34*8975f5c5SAndroid Build Coastguard Worker // number of mantissa bits per component pre-biased
35*8975f5c5SAndroid Build Coastguard Worker constexpr int g_sharedexp_biased_mantissabits = g_sharedexp_bias + g_sharedexp_mantissabits;
36*8975f5c5SAndroid Build Coastguard Worker 
37*8975f5c5SAndroid Build Coastguard Worker // Emax is the maximum allowed biased exponent value (31)
38*8975f5c5SAndroid Build Coastguard Worker constexpr int g_sharedexp_maxexponent = 31;
39*8975f5c5SAndroid Build Coastguard Worker 
40*8975f5c5SAndroid Build Coastguard Worker constexpr float g_sharedexp_max =
41*8975f5c5SAndroid Build Coastguard Worker     ((static_cast<float>(1 << g_sharedexp_mantissabits) - 1) /
42*8975f5c5SAndroid Build Coastguard Worker      static_cast<float>(1 << g_sharedexp_mantissabits)) *
43*8975f5c5SAndroid Build Coastguard Worker     static_cast<float>(1 << (g_sharedexp_maxexponent - g_sharedexp_bias));
44*8975f5c5SAndroid Build Coastguard Worker 
45*8975f5c5SAndroid Build Coastguard Worker }  // anonymous namespace
46*8975f5c5SAndroid Build Coastguard Worker 
convertRGBFloatsTo999E5(float red,float green,float blue)47*8975f5c5SAndroid Build Coastguard Worker unsigned int convertRGBFloatsTo999E5(float red, float green, float blue)
48*8975f5c5SAndroid Build Coastguard Worker {
49*8975f5c5SAndroid Build Coastguard Worker     const float red_c   = std::max<float>(0, std::min(g_sharedexp_max, red));
50*8975f5c5SAndroid Build Coastguard Worker     const float green_c = std::max<float>(0, std::min(g_sharedexp_max, green));
51*8975f5c5SAndroid Build Coastguard Worker     const float blue_c  = std::max<float>(0, std::min(g_sharedexp_max, blue));
52*8975f5c5SAndroid Build Coastguard Worker 
53*8975f5c5SAndroid Build Coastguard Worker     const float max_c = std::max<float>({red_c, green_c, blue_c});
54*8975f5c5SAndroid Build Coastguard Worker     const float exp_p =
55*8975f5c5SAndroid Build Coastguard Worker         std::max<float>(-g_sharedexp_bias - 1, floor(log(max_c))) + 1 + g_sharedexp_bias;
56*8975f5c5SAndroid Build Coastguard Worker     const int max_s = static_cast<int>(
57*8975f5c5SAndroid Build Coastguard Worker         floor((max_c / (pow(2.0f, exp_p - g_sharedexp_biased_mantissabits))) + 0.5f));
58*8975f5c5SAndroid Build Coastguard Worker     const int exp_s =
59*8975f5c5SAndroid Build Coastguard Worker         static_cast<int>((max_s < pow(2.0f, g_sharedexp_mantissabits)) ? exp_p : exp_p + 1);
60*8975f5c5SAndroid Build Coastguard Worker     const float pow2_exp = pow(2.0f, static_cast<float>(exp_s) - g_sharedexp_biased_mantissabits);
61*8975f5c5SAndroid Build Coastguard Worker 
62*8975f5c5SAndroid Build Coastguard Worker     RGB9E5Data output;
63*8975f5c5SAndroid Build Coastguard Worker     output.R = static_cast<unsigned int>(floor((red_c / pow2_exp) + 0.5f));
64*8975f5c5SAndroid Build Coastguard Worker     output.G = static_cast<unsigned int>(floor((green_c / pow2_exp) + 0.5f));
65*8975f5c5SAndroid Build Coastguard Worker     output.B = static_cast<unsigned int>(floor((blue_c / pow2_exp) + 0.5f));
66*8975f5c5SAndroid Build Coastguard Worker     output.E = exp_s;
67*8975f5c5SAndroid Build Coastguard Worker 
68*8975f5c5SAndroid Build Coastguard Worker     return bitCast<unsigned int>(output);
69*8975f5c5SAndroid Build Coastguard Worker }
70*8975f5c5SAndroid Build Coastguard Worker 
convert999E5toRGBFloats(unsigned int input,float * red,float * green,float * blue)71*8975f5c5SAndroid Build Coastguard Worker void convert999E5toRGBFloats(unsigned int input, float *red, float *green, float *blue)
72*8975f5c5SAndroid Build Coastguard Worker {
73*8975f5c5SAndroid Build Coastguard Worker     const RGB9E5Data *inputData = reinterpret_cast<const RGB9E5Data *>(&input);
74*8975f5c5SAndroid Build Coastguard Worker 
75*8975f5c5SAndroid Build Coastguard Worker     const float pow2_exp =
76*8975f5c5SAndroid Build Coastguard Worker         pow(2.0f, static_cast<float>(inputData->E) - g_sharedexp_biased_mantissabits);
77*8975f5c5SAndroid Build Coastguard Worker 
78*8975f5c5SAndroid Build Coastguard Worker     *red   = inputData->R * pow2_exp;
79*8975f5c5SAndroid Build Coastguard Worker     *green = inputData->G * pow2_exp;
80*8975f5c5SAndroid Build Coastguard Worker     *blue  = inputData->B * pow2_exp;
81*8975f5c5SAndroid Build Coastguard Worker }
82*8975f5c5SAndroid Build Coastguard Worker 
83*8975f5c5SAndroid Build Coastguard Worker }  // namespace gl
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