OpenCV 实战 - 图像融合（cv::copyTo()）

cv::copyTo()

OpenCV 中 cv::copyTo 是用来复制矩阵对象 Mat 的，可以实现直接创建一个副本，且在副本矩阵上的操作不会影响原矩阵。

cv::copyTo() 声明

 /** @brief Copies the matrix to another one.

The method copies the matrix data to another matrix. Before copying the data, the method invokes :
@code
    m.create(this->size(), this->type());
@endcode
so that the destination matrix is reallocated if needed. While m.copyTo(m); works flawlessly, the function does not handle the case of a partial overlap between the source and the destination matrices.

When the operation mask is specified, if the Mat::create call shown above reallocates the matrix, the newly allocated matrix is initialized with all zeros before copying the data.
@param m Destination matrix. If it does not have a proper size or type before the operation, it is reallocated.
 */
void copyTo( OutputArray m ) const;

同时 cv::copyTo() 被重载了，声明如下：

/** @overload
@param m Destination matrix. If it does not have a proper size or type before the operation, it is reallocated.
@param mask Operation mask of the same size as \*this. Its non-zero elements indicate which matrix elements need to be copied. The mask has to be of type CV_8U and can have 1 or multiple channels.
*/
void copyTo( OutputArray m, InputArray mask ) const;

可以看到重载处注释：第二个参数 mask 的尺寸与原图像相同，它的非零元素表示需要复制的矩阵元素，mask 必须是 CV_8U 类型的，可以有 1 个或多个通道。

测试

下图是两张 1000*1000 的图像

目标是将两张图像叠在一起，同时在第一张图像中的白色圆形区域内复制第二张图像的对应区域，即完成图像融合，形成如下效果。

由于 cv::copyTo 可以复制将 mask 矩阵中的非零元素的位置对应于原图像中该位置的值，从而可以实现图像融合，代码如下：

#include <iostream>
#include <sstream>
#include <fstream>

#include <opencv2/core/core.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/imgcodecs/imgcodecs.hpp>
#include <opencv2/highgui/highgui.hpp>

#define background "0_background.png"
#define foreground "HappyFish.jpg"

void image_fusion1(cv::Mat& matBackGround, cv::Mat& matForeGround, cv::Mat& matFusion);

int main(int argc, char** argv)
{
	cv::Mat matBackGround;
	cv::Mat matForeGround;

	cv::Mat matFusion;

	image_fusion1(matBackGround, matForeGround, matFusion);

	return 0;
}

void image_fusion1(cv::Mat& matBackGround, cv::Mat& matForeGround, cv::Mat& matFusion)
{
	matBackGround = cv::imread(cv::samples::findFile(background), cv::IMREAD_COLOR);
	matForeGround = cv::imread(cv::samples::findFile(foreground), cv::IMREAD_COLOR);

	//cv::namedWindow("Background", cv::WINDOW_AUTOSIZE);
	//cv::namedWindow("Foreground", cv::WINDOW_AUTOSIZE);
	//cv::namedWindow("Image Fusion", cv::WINDOW_AUTOSIZE);

	matForeGround.copyTo(matFusion, matBackGround);

	cv::imshow("Background", matBackGround);
	cv::imshow("Foreground", matForeGround);
	cv::imshow("Image Fusion", matFusion);

	cv::imwrite("Image Fusion.png", matFusion);

	cv::waitKey(0);
}