OpenCV代码提取：transpose函数的实现

OpenCV中的transpose函数实现图像转置，公式为：

目前fbc_cv库中也实现了transpose函数，支持多通道，uchar和float两种数据类型，经测试，与OpenCV3.1结果完全一致。

实现代码transpose.hpp：

// fbc_cv is free software and uses the same licence as OpenCV
// Email: [email protected]

#ifndef FBC_CV_TRANSPOSE_HPP_
#define FBC_CV_TRANSPOSE_HPP_

/* reference: include/opencv2/core.hpp
              modules/core/src/matrix.cpp
*/

#include <typeinfo>
#include "core/mat.hpp"

namespace fbc {

// transposes the matrix
// \f[\texttt{dst} (i,j) =  \texttt{src} (j,i)\f]
// support type: uchar/float, multi-channels
template <typename _Tp, int chs>
int transpose(const Mat_<_Tp, chs>& src, Mat_<_Tp, chs>& dst)
{
	FBC_Assert(typeid(uchar).name() == typeid(_Tp).name() || typeid(float).name() == typeid(_Tp).name()); // uchar || float
	if (dst.empty()) {
		dst = Mat_<_Tp, chs>(src.cols, src.rows);
	} else {
		FBC_Assert(src.rows == dst.cols && src.cols == dst.rows);
	}

	if (src.empty()) {
		dst.release();
		return 0;
	}

	// handle the case of single-column/single-row matrices, stored in STL vectors.
	if (src.rows != dst.cols || src.cols != dst.rows) {
		FBC_Assert(src.size() == dst.size() && (src.cols == 1 || src.rows == 1));
		src.copyTo(dst);
		return 0;
	}

	if (dst.data == src.data) {
		FBC_Assert(dst.cols == dst.rows);
		int n = dst.rows;
		int  step = dst.step;
		uchar* data = dst.ptr();

		for (int i = 0; i < n; i++) {
			_Tp* row = (_Tp*)(data + step*i);
			int i_ = i * chs;

			for (int j = i + 1; j < n; j++) {
				_Tp* data1 = (_Tp*)(data + step * j);
				int j_ = j * chs;

				for (int ch = 0; ch < chs; ch++) {
					std::swap(row[j_ + ch], data1[i_ + ch]);
				}
			}
		}
	} else {
		const uchar* src_ = src.ptr();
		size_t sstep = src.step;
		uchar* dst_ = dst.ptr();
		size_t dstep = dst.step;
		int m = src.cols, n = src.rows;

		for (int i = 0; i < n; i++) {
			const _Tp* s = (const _Tp*)(src_ + sstep*i);
			int i_ = i * chs;

			for (int j = 0; j < m; j++) {
				_Tp* d = (_Tp*)(dst_ + dstep*j);
				int j_ = j * chs;

				for (int ch = 0; ch < chs; ch++) {
					d[i_ + ch] = s[j_ + ch];
				}
			}
		}
	}

	return 0;
}

} // namespace fbc

#endif // FBC_CV_TRANSPOSE_HPP_

测试代码test_transpose.cpp：

#include "test_transpose.hpp"
#include <assert.h>
#include <iostream>
#include <string>
#include <opencv2/opencv.hpp>
#include <transpose.hpp>

int test_transpose_uchar()
{
	cv::Mat matSrc = cv::imread("E:/GitCode/OpenCV_Test/test_images/lena.png", 1);
	if (!matSrc.data) {
		std::cout << "read image fail" << std::endl;
		return -1;
	}

	int width = matSrc.cols;
	int height = matSrc.rows;
	cv::Mat matSrc_;
	cv::resize(matSrc, matSrc_, cv::Size(width, width));

	fbc::Mat_<uchar, 3> mat1(width, width);
	memcpy(mat1.data, matSrc_.data, width * width * 3);
	fbc::transpose(mat1, mat1);

	cv::Mat mat1_(width, width, CV_8UC3);
	memcpy(mat1_.data, matSrc_.data, width * width * 3);
	cv::transpose(mat1_, mat1_);

	assert(mat1.rows == mat1_.rows && mat1.cols == mat1_.cols && mat1.step == mat1_.step);
	for (int y = 0; y < mat1.rows; y++) {
		const fbc::uchar* p1 = mat1.ptr(y);
		const uchar* p2 = mat1_.ptr(y);

		for (int x = 0; x < mat1.step; x++) {
			assert(p1[x] == p2[x]);
		}
	}

	cv::Mat matSave(width, width, CV_8UC3, mat1.data);
	cv::imwrite("E:/GitCode/OpenCV_Test/test_images/transpose_fbc.jpg", matSave);
	cv::imwrite("E:/GitCode/OpenCV_Test/test_images/transpose_cv.jpg", mat1_);

	cv::Mat matSrc1 = cv::imread("E:/GitCode/OpenCV_Test/test_images/1.jpg", 1);
	if (!matSrc1.data) {
		std::cout << "read image fail" << std::endl;
		return -1;
	}

	width = matSrc1.cols;
	height = matSrc1.rows;

	fbc::Mat_<uchar, 3> mat2(height, width, matSrc1.data);
	fbc::Mat_<uchar, 3> mat3(width, height);
	fbc::transpose(mat2, mat3);

	cv::Mat mat2_(height, width, CV_8UC3, matSrc1.data);
	cv::Mat mat3_;
	cv::transpose(mat2_, mat3_);

	assert(mat3.rows == mat3_.rows && mat3.cols == mat3_.cols && mat3.step == mat3_.step);
	for (int y = 0; y < mat3.rows; y++) {
		const fbc::uchar* p1 = mat3.ptr(y);
		const uchar* p2 = mat3_.ptr(y);

		for (int x = 0; x < mat3.step; x++) {
			assert(p1[x] == p2[x]);
		}
	}

	cv::Mat matSave1(width, height, CV_8UC3, mat3.data);
	cv::imwrite("E:/GitCode/OpenCV_Test/test_images/transpose1_fbc.jpg", matSave1);
	cv::imwrite("E:/GitCode/OpenCV_Test/test_images/transpose1_cv.jpg", mat3_);

	return 0;
}

int test_transpose_float()
{
	cv::Mat matSrc = cv::imread("E:/GitCode/OpenCV_Test/test_images/lena.png", 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;
	cv::Mat matSrc_;
	cv::resize(matSrc, matSrc_, cv::Size(width, width));

	fbc::Mat_<float, 1> mat1(width, width);
	memcpy(mat1.data, matSrc_.data, width * width * sizeof(float));
	fbc::transpose(mat1, mat1);

	cv::Mat mat1_(width, width, CV_32FC1);
	memcpy(mat1_.data, matSrc_.data, width * width * sizeof(float));
	cv::transpose(mat1_, mat1_);

	assert(mat1.rows == mat1_.rows && mat1.cols == mat1_.cols && mat1.step == mat1_.step);
	for (int y = 0; y < mat1.rows; y++) {
		const fbc::uchar* p1 = mat1.ptr(y);
		const uchar* p2 = mat1_.ptr(y);

		for (int x = 0; x < mat1.step; x++) {
			assert(p1[x] == p2[x]);
		}
	}

	cv::Mat matSrc1 = cv::imread("E:/GitCode/OpenCV_Test/test_images/1.jpg", 1);
	if (!matSrc1.data) {
		std::cout << "read image fail" << std::endl;
		return -1;
	}
	cv::cvtColor(matSrc1, matSrc1, CV_BGR2GRAY);
	matSrc1.convertTo(matSrc1, CV_32FC1);

	width = matSrc1.cols;
	height = matSrc1.rows;

	fbc::Mat_<float, 1> mat2(height, width, matSrc1.data);
	fbc::Mat_<float, 1> mat3(width, height);
	fbc::transpose(mat2, mat3);

	cv::Mat mat2_(height, width, CV_32FC1, matSrc1.data);
	cv::Mat mat3_;
	cv::transpose(mat2_, mat3_);

	assert(mat3.rows == mat3_.rows && mat3.cols == mat3_.cols && mat3.step == mat3_.step);
	for (int y = 0; y < mat3.rows; y++) {
		const fbc::uchar* p1 = mat3.ptr(y);
		const uchar* p2 = mat3_.ptr(y);

		for (int x = 0; x < mat3.step; x++) {
			assert(p1[x] == p2[x]);
		}
	}

	return 0;
}

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