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