OpenCV中實現圖像翻轉的函數flip，公式為：

目前fbc_cv庫中也實現了flip函數，支持多通道，uchar和float兩種數據類型，經測試，與OpenCV3.1結果完全一致。

實現代碼flip.hpp：

// fbc_cv is free software and uses the same licence as OpenCV
// Email: fengbingchun@163.com#ifndef FBC_CV_FLIP_HPP_
#define FBC_CV_FLIP_HPP_/* reference: include/opencv2/core.hppmodules/core/src/copy.cpp
*/#include <typeinfo>
#include "core/mat.hpp"namespace fbc {template<typename _Tp, int chs> static int flipHoriz(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst);
template<typename _Tp, int chs> static int flipVert(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst);// Flips a 2D array around vertical, horizontal, or both axes
// flipCode: 0 means flipping around the x - axis and positive value means flipping around y - axis.
//	     Negative value means flipping around both axes
// support type: uchar/float, multi-channels
template <typename _Tp, int chs>
int flip(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst, int flipCode)
{FBC_Assert(typeid(uchar).name() == typeid(_Tp).name() || typeid(float).name() == typeid(_Tp).name()); // uchar || floatif (dst.empty()) {dst = Mat_<_Tp, chs>(src.rows, src.cols);} else {FBC_Assert(src.rows == dst.rows && src.cols == dst.cols);}Size size = src.size();if (flipCode < 0) {if (size.width == 1)flipCode = 0;if (size.height == 1)flipCode = 1;}if ((size.width == 1 && flipCode > 0) ||(size.height == 1 && flipCode == 0) ||(size.height == 1 && size.width == 1 && flipCode < 0)) {src.copyTo(dst);return 0;}if (flipCode <= 0)flipVert(src, dst);elseflipHoriz(src, dst);if (flipCode < 0)flipHoriz(dst, dst);return 0;
}template<typename _Tp, int chs>
static int flipHoriz(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst)
{Size size = src.size();size_t esz = sizeof(_Tp) * chs;int i, j, limit = (int)(((size.width + 1) / 2) *esz );AutoBuffer<int> _tab(size.width * esz);int* tab = _tab;size_t sstep = src.step;size_t dstep = dst.step;const uchar* src_ = src.ptr();uchar* dst_ = dst.ptr();for (i = 0; i < size.width; i++) {for (size_t k = 0; k < esz; k++) {tab[i*esz + k] = (int)((size.width - i - 1) * esz + k);}}for (; size.height--; src_ += sstep, dst_ += dstep) {for (i = 0; i < limit; i++) {j = tab[i];uchar t0 = src_[i], t1 = src_[j];dst_[i] = t1; dst_[j] = t0;}}return 0;
}template<typename _Tp, int chs>
static int flipVert(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst)
{const uchar* src0 = src.ptr();uchar* dst0 = dst.ptr();Size size = src.size();size_t sstep = src.step;size_t dstep = dst.step;size_t esz = sizeof(_Tp) * chs;const uchar* src1 = src0 + (size.height - 1)*sstep;uchar* dst1 = dst0 + (size.height - 1)*dstep;size.width *= (int)esz;for (int y = 0; y < (size.height + 1) / 2; y++, src0 += sstep, src1 -= sstep, dst0 += dstep, dst1 -= dstep) {int i = 0;if (((size_t)src0 | (size_t)dst0 | (size_t)src1 | (size_t)dst1) % sizeof(int) == 0) {for (; i <= size.width - 16; i += 16) {int t0 = ((int*)(src0 + i))[0];int t1 = ((int*)(src1 + i))[0];((int*)(dst0 + i))[0] = t1;((int*)(dst1 + i))[0] = t0;t0 = ((int*)(src0 + i))[1];t1 = ((int*)(src1 + i))[1];((int*)(dst0 + i))[1] = t1;((int*)(dst1 + i))[1] = t0;t0 = ((int*)(src0 + i))[2];t1 = ((int*)(src1 + i))[2];((int*)(dst0 + i))[2] = t1;((int*)(dst1 + i))[2] = t0;t0 = ((int*)(src0 + i))[3];t1 = ((int*)(src1 + i))[3];((int*)(dst0 + i))[3] = t1;((int*)(dst1 + i))[3] = t0;}for (; i <= size.width - 4; i += 4) {int t0 = ((int*)(src0 + i))[0];int t1 = ((int*)(src1 + i))[0];((int*)(dst0 + i))[0] = t1;((int*)(dst1 + i))[0] = t0;}}for (; i < size.width; i++) {uchar t0 = src0[i];uchar t1 = src1[i];dst0[i] = t1;dst1[i] = t0;}}return 0;
}} // namespace fbc#endif // FBC_CV_FLIP_HPP_

測試代碼test_flip.cpp：

#include "test_flip.hpp"
#include <assert.h>
#include <iostream>
#include <string>#include <flip.hpp>
#include <opencv2/opencv.hpp>int test_flip_uchar()
{cv::Mat matSrc = cv::imread("E:/GitCode/OpenCV_Test/test_images/1.jpg", 1);if (!matSrc.data) {std::cout << "read image fail" << std::endl;return -1;}int width = matSrc.cols;int height = matSrc.rows;int flipCode[3] {-1, 0, 1}; // both axes, x axis, y axisfor (int i = 0; i < 3; i++) {fbc::Mat_<uchar, 3> mat1(height, width, matSrc.data);fbc::Mat_<uchar, 3> mat2(height, width);fbc::flip(mat1, mat2, flipCode[i]);cv::Mat mat1_(height, width, CV_8UC3, matSrc.data);cv::Mat mat2_;cv::flip(mat1_, mat2_, flipCode[i]);assert(mat2.rows == mat2_.rows && mat2.cols == mat2_.cols && mat2.step == mat2_.step);for (int y = 0; y < mat2.rows; y++) {const fbc::uchar* p1 = mat2.ptr(y);const uchar* p2 = mat2_.ptr(y);for (int x = 0; x < mat2.step; x++) {assert(p1[x] == p2[x]);}}std::string name = std::to_string(i);std::string file_path = "E:/GitCode/OpenCV_Test/test_images/";std::string name_fbc = file_path + "flip_fbc_" + name + ".jpg";std::string name_cv = file_path + "flip_cv_" + name + ".jpg";cv::Mat matSave(height, width, CV_8UC3, mat2.data);cv::imwrite(name_fbc, matSave);cv::imwrite(name_cv, mat2_);}return 0;
}int test_flip_float()
{cv::Mat matSrc = cv::imread("E:/GitCode/OpenCV_Test/test_images/1.jpg", 1);if (!matSrc.data) {std::cout << "read image fail" << std::endl;return -1;}cv::cvtColor(matSrc, matSrc, CV_BGR2GRAY);matSrc.convertTo(matSrc, CV_32FC1);int width = matSrc.cols;int height = matSrc.rows;int flipCode[3] {-1, 0, 1}; // both axes, x axis, y axisfor (int i = 0; i < 3; i++) {fbc::Mat_<float, 1> mat1(height, width, matSrc.data);fbc::Mat_<float, 1> mat2(height, width);fbc::flip(mat1, mat2, flipCode[i]);cv::Mat mat1_(height, width, CV_32FC1, matSrc.data);cv::Mat mat2_;cv::flip(mat1_, mat2_, flipCode[i]);assert(mat2.rows == mat2_.rows && mat2.cols == mat2_.cols && mat2.step == mat2_.step);for (int y = 0; y < mat2.rows; y++) {const fbc::uchar* p1 = mat2.ptr(y);const uchar* p2 = mat2_.ptr(y);for (int x = 0; x < mat2.step; x++) {assert(p1[x] == p2[x]);}}}return 0;
}

GitHub： https://github.com/fengbingchun/OpenCV_Test