LinearTransform.h revision d4d6167f614a9001d9827a8634a26b5e9445a22c
1/* 2 * Copyright (C) 2011 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17#ifndef _LINEAR_TRANSFORM_H 18#define _LINEAR_TRANSFORM_H 19 20#include <stdint.h> 21 22namespace android { 23 24// LinearTransform defines a structure which hold the definition of a 25// transformation from single dimensional coordinate system A into coordinate 26// system B (and back again). Values in A and in B are 64 bit, the linear 27// scale factor is expressed as a rational number using two 32 bit values. 28// 29// Specifically, let 30// f(a) = b 31// F(b) = f^-1(b) = a 32// then 33// 34// f(a) = (((a - a_zero) * a_to_b_numer) / a_to_b_denom) + b_zero; 35// 36// and 37// 38// F(b) = (((b - b_zero) * a_to_b_denom) / a_to_b_numer) + a_zero; 39// 40struct LinearTransform { 41 int64_t a_zero; 42 int64_t b_zero; 43 int32_t a_to_b_numer; 44 uint32_t a_to_b_denom; 45 46 // Transform from A->B 47 // Returns true on success, or false in the case of a singularity or an 48 // overflow. 49 bool doForwardTransform(int64_t a_in, int64_t* b_out) const; 50 51 // Transform from B->A 52 // Returns true on success, or false in the case of a singularity or an 53 // overflow. 54 bool doReverseTransform(int64_t b_in, int64_t* a_out) const; 55 56 // Helpers which will reduce the fraction N/D using Euclid's method. 57 template <class T> static void reduce(T* N, T* D); 58 static void reduce(int32_t* N, uint32_t* D); 59}; 60 61 62} 63 64#endif // _LINEAR_TRANSFORM_H 65