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Photoshop中的套索工具通过鼠标多次点击可以选中一个任意多边形的区域，然后单独对这块区域进行编辑，下面就使用OpenCV实现一个简单的功能，模拟Photoshop中的套索工具。
这里的套索工具通过鼠标左键在图片上多次点击创建任意多个点，右键点击后将这些点连成封闭的多边形，形成一块待编辑的区域，键盘方向键控制该区域的移动，从而将该区域内的图像复制到原图像的其他地方。
首先定义下列全局变量
const char* winName = "TaoSuoTool";//窗口名称cv::Mat resultImg;//最终在OpenCV窗口上显示的图像cv::Mat foregroundImg;//编辑前的图像cv::Mat areaMask;//蒙版，多边形区域实际绘制在该蒙版上cv::Point maskLocation;//蒙版位置，通过方向键移动后蒙版位置随之变化std::vector<cv::Point> drawingPoints;//区域完成前正在点击的所有点std::vector<cv::Point> areaPoints;//区域完成后其多边形顶点main函数
int main(int argc, char **arv){ foregroundImg = cv::imread("test.jpg"); foregroundImg.copyTo(resultImg); areaMask = cv::Mat::zeros(foregroundImg.size(), CV_8U); cv::imshow(winName, resultImg); maskLocation.x = maskLocation.y = 0; cv::setMouseCallback(winName, OnMouseEvent); int key = cv::waitKeyEx(0); while (key != VK_ESCAPE) { key = cv::waitKeyEx(0); } return 0;}在鼠标回调函数OnMouseEvent中处理三个消息：鼠标左键按下，鼠标右键按下和鼠标移动
void OnMouseEvent(int event, int x, int y, int flags, void* userdata){ if (event == cv::EVENT_LBUTTONDOWN) { OnLeftMouseButtonDown(x,y); } else if (event == cv::EVENT_RBUTTONDOWN) { OnRightMouseButtonDown(x,y); } if (event == cv::EVENT_MOUSEMOVE) { OnMouseMove(x,y); }}在编写鼠标事件前先定义一个函数
void OnCompleteArea(bool bDrawOutline);它表示完成当前区域的编辑，包括右键点击完成封闭多边形、移动区域以及合成最终图片。参数bDrawOutline表示绘制区域多边形的外轮廓，右键点击完成封闭多边形和移动区域过程中都要显示轮廓(bDrawOutline=true)，合成最终图片后就不需要显示轮廓了(bDrawOutline=false)。
鼠标左键按下事件：先判断是否有前一个区域存在，存在则先完成前一个区域并且不显示区域轮廓，然后开始绘制新的区域多边形的点，点与点之间用蓝色线连接，点位置处绘制一个4X4的红色矩形。
void OnLeftMouseButtonDown(int x,int y){ if (drawingPoints.empty() && areaPoints.size() > 0) { OnCompleteArea(false); } drawingPoints.push_back(cv::Point(x, y)); cv::rectangle(resultImg, cv::Rect(x - 2, y - 2, 4, 4), CV_RGB(255, 0, 0), -1); if (drawingPoints.size() >= 2) { cv::line(resultImg, drawingPoints[drawingPoints.size() - 2], cv::Point(x, y), CV_RGB(0, 0, 255), 1); } cv::imshow(winName, resultImg);}鼠标移动事件：判断drawingPoints是否为空，如果已经存在点则绘制线和点，并且还要绘制一根连接到鼠标当前位置的线。
void OnMouseMove(int x,int y){ if (drawingPoints.size() > 0) { foregroundImg.copyTo(resultImg); for (int i = 0; i < drawingPoints.size() - 1; i++) { cv::rectangle(resultImg, cv::Rect(drawingPoints[i].x - 2, drawingPoints[i].y - 2, 4, 4), CV_RGB(255, 0, 0), -1); cv::line(resultImg, drawingPoints[i], drawingPoints[i + 1], CV_RGB(0, 0, 255), 1); } cv::rectangle(resultImg, cv::Rect(drawingPoints[drawingPoints.size() - 1].x - 2, drawingPoints[drawingPoints.size() - 1].y - 2, 4, 4), CV_RGB(255, 0, 0), -1); cv::line(resultImg, drawingPoints[drawingPoints.size() - 1], cv::Point(x, y), CV_RGB(0, 0, 255), 1); cv::imshow(winName, resultImg); }}鼠标右键按下事件：如果点个数少于2，不能形成有效区域则不做处理（不考虑多个点共线），否则就在蒙版Area上绘制一个多边形区域，然后调用OnCompleteArea完成区域编辑，这里需要画多边形轮廓，参数传入true。
void OnRightMouseButtonDown(int x,int y){ if (drawingPoints.size() >= 3) { areaPoints = drawingPoints; std::vector<std::vector<cv::Point>> polys; polys.push_back(areaPoints); cv::fillPoly(areaMask, polys, cv::Scalar::all(255)); OnCompleteArea(true); } else { foregroundImg.copyTo(resultImg); } drawingPoints.clear(); cv::imshow(winName, resultImg);}下面是OnCompleteArea函数的实现，其中MergeImages函数通过蒙版以及蒙版的位置合成最终的图像，蒙版中区域内的像素值大于0，其他像素值都为0，默认图像是三通道(destImg.at<cv::Vec3b>)
void MergeImages(cv::Mat& destImg, const cv::Mat& srcImg, const cv::Mat& maskImg, int x, int y){ int top = y > 0 ? y : 0; int left = x > 0 ? x : 0; int right = destImg.cols > x + srcImg.cols ? x + srcImg.cols : destImg.cols; int bottom = destImg.rows > y + srcImg.rows ? y + srcImg.rows : destImg.rows; for (int i = top; i < bottom; i++) { for (int j = left; j < right; j++) { int destIndex = i * destImg.cols + j; int srcIndex = (i - top)*srcImg.cols + j - left; int channel = destImg.channels(); if (maskImg.at<uchar>(i - y, j - x) > 0) { destImg.at<cv::Vec3b>(i, j)[0] = srcImg.at<cv::Vec3b>(i - y, j - x)[0]; destImg.at<cv::Vec3b>(i, j)[1] = srcImg.at<cv::Vec3b>(i - y, j - x)[1]; destImg.at<cv::Vec3b>(i, j)[2] = srcImg.at<cv::Vec3b>(i - y, j - x)[2]; } } }}void OnCompleteArea(bool bDrawOutline){ foregroundImg.copyTo(resultImg); MergeImages(resultImg, foregroundImg, areaMask, maskLocation.x, maskLocation.y); if (bDrawOutline) { if (areaPoints.size() >= 3) { std::vector<std::vector<cv::Point>> polys; polys.push_back(areaPoints); cv::polylines(resultImg, polys, true, cv::Scalar::all(255)); } } else { resultImg.copyTo(foregroundImg); areaPoints.clear(); memset(areaMask.data, 0, areaMask.rows*areaMask.cols*areaMask.elemSize()); maskLocation.x = maskLocation.y = 0; }}绘制区域之后就可以通过方向按键控制区域图像的移动了（也可以实现为鼠标左键按下拖动来移动区域），移动主要是更新maskLocation和areaPoints的坐标值，然后调用OnCompleteArea(true)，依然显示区域的轮廓。
void OnDirectionKeyDown(short keyCode){ int x = keyCode == VK_LEFT ? -2 : (keyCode == VK_RIGHT ? 2 : 0); int y = keyCode == VK_UP ? -2 : (keyCode == VK_DOWN ? 2 : 0); maskLocation.x += x; maskLocation.y += y; for (int i = 0; i < areaPoints.size(); i++) { areaPoints[i].x += x; areaPoints[i].y += y; } OnCompleteArea(true); cv::imshow(winName, resultImg);}将上面函数在主函数的按键循环中调用，方向按键通过key的高16位判断，在Windows下可以使用虚拟键码宏表示。 同时为了能看到最终合成的图片加入Enter按键消息处理，将图像合成并去掉轮廓。
int key = cv::waitKeyEx(0);short lowKey = key;short highKey = key >> 16;while (key != VK_ESCAPE){ if (key == VK_RETURN)//Enter { OnCompleteArea(false); cv::imshow(winName, resultImg); } else if (lowKey == 0 && (highKey == VK_UP || highKey == VK_DOWN || highKey == VK_LEFT || highKey == VK_RIGHT)) { OnDirectionKeyDown(highKey); } key = cv::waitKeyEx(0); lowKey = key; highKey = key >> 16;}这样一个简单的套索工具功能就做好了（上面的代码都是简化处理，还有很多可以优化的地方，从而使编辑更加流畅）
完整代码
#include<iostream>#include"opencv2/opencv.hpp"#include<windows.h>const char* winName = "TaoSuoTool";cv::Point maskLocation;cv::Mat resultImg;cv::Mat foregroundImg;cv::Mat areaMask;std::vector<cv::Point> drawingPoints;std::vector<cv::Point> areaPoints;void MergeImages(cv::Mat& destImg, const cv::Mat& srcImg, const cv::Mat& maskImg, int x, int y){ int top = y > 0 ? y : 0; int left = x > 0 ? x : 0; int right = destImg.cols > x + srcImg.cols ? x + srcImg.cols : destImg.cols; int bottom = destImg.rows > y + srcImg.rows ? y + srcImg.rows : destImg.rows; for (int i = top; i < bottom; i++) { for (int j = left; j < right; j++) { int destIndex = i * destImg.cols + j; int srcIndex = (i - top)*srcImg.cols + j - left; int channel = destImg.channels(); if (maskImg.at<uchar>(i - y, j - x) > 0) { destImg.at<cv::Vec3b>(i, j)[0] = srcImg.at<cv::Vec3b>(i - y, j - x)[0]; destImg.at<cv::Vec3b>(i, j)[1] = srcImg.at<cv::Vec3b>(i - y, j - x)[1]; destImg.at<cv::Vec3b>(i, j)[2] = srcImg.at<cv::Vec3b>(i - y, j - x)[2]; } } }} void OnCompleteArea(bool bDrawOutline){ foregroundImg.copyTo(resultImg); MergeImages(resultImg, foregroundImg, areaMask, maskLocation.x, maskLocation.y); if (bDrawOutline) { if (areaPoints.size() >= 3) { std::vector<std::vector<cv::Point>> polys; polys.push_back(areaPoints); cv::polylines(resultImg, polys, true, cv::Scalar::all(255)); } } else { resultImg.copyTo(foregroundImg); areaPoints.clear(); memset(areaMask.data, 0, areaMask.rows*areaMask.cols*areaMask.elemSize()); maskLocation.x = maskLocation.y = 0; }}void OnLeftMouseButtonDown(int x,int y){ if (drawingPoints.empty() && areaPoints.size() > 0) { OnCompleteArea(false); } drawingPoints.push_back(cv::Point(x, y)); cv::rectangle(resultImg, cv::Rect(x - 2, y - 2, 4, 4), CV_RGB(255, 0, 0), -1); if (drawingPoints.size() >= 2) { cv::line(resultImg, drawingPoints[drawingPoints.size() - 2], cv::Point(x, y), CV_RGB(0, 0, 255), 1); } cv::imshow(winName, resultImg);}void OnRightMouseButtonDown(int x,int y){ if (drawingPoints.size() >= 3) { areaPoints = drawingPoints; std::vector<std::vector<cv::Point>> polys; polys.push_back(areaPoints); cv::fillPoly(areaMask, polys, cv::Scalar::all(255)); OnCompleteArea(true); } else { foregroundImg.copyTo(resultImg); } drawingPoints.clear(); cv::imshow(winName, resultImg);}void OnMouseMove(int x,int y){ if (drawingPoints.size() > 0) { foregroundImg.copyTo(resultImg); for (int i = 0; i < drawingPoints.size() - 1; i++) { cv::rectangle(resultImg, cv::Rect(drawingPoints[i].x - 2, drawingPoints[i].y - 2, 4, 4), CV_RGB(255, 0, 0), -1); cv::line(resultImg, drawingPoints[i], drawingPoints[i + 1], CV_RGB(0, 0, 255), 1); } cv::rectangle(resultImg, cv::Rect(drawingPoints[drawingPoints.size() - 1].x - 2, drawingPoints[drawingPoints.size() - 1].y - 2, 4, 4), CV_RGB(255, 0, 0), -1); cv::line(resultImg, drawingPoints[drawingPoints.size() - 1], cv::Point(x, y), CV_RGB(0, 0, 255), 1); cv::imshow(winName, resultImg); }}void OnMouseEvent(int event, int x, int y, int flags, void* userdata){ if (event == cv::EVENT_LBUTTONDOWN) { OnLeftMouseButtonDown(x,y); } else if (event == cv::EVENT_RBUTTONDOWN) { OnRightMouseButtonDown(x,y); } if (event == cv::EVENT_MOUSEMOVE) { OnMouseMove(x,y); }} void OnDirectionKeyDown(short keyCode){ int x = keyCode == VK_LEFT ? -2 : (keyCode == VK_RIGHT ? 2 : 0); int y = keyCode == VK_UP ? -2 : (keyCode == VK_DOWN ? 2 : 0); maskLocation.x += x; maskLocation.y += y; for (int i = 0; i < areaPoints.size(); i++) { areaPoints[i].x += x; areaPoints[i].y += y; } OnCompleteArea(true); cv::imshow(winName, resultImg);}int main(int argc, char **arv){ foregroundImg = cv::imread("test.jpg"); foregroundImg.copyTo(resultImg); areaMask = cv::Mat::zeros(foregroundImg.size(), CV_8U); cv::imshow(winName, resultImg); maskLocation.x = maskLocation.y = 0; cv::setMouseCallback(winName, OnMouseEvent); int key = cv::waitKeyEx(0); short lowKey = key; short highKey = key >> 16; while (key != VK_ESCAPE) { if (key == VK_RETURN)//Enter { OnCompleteArea(false); cv::imshow(winName, resultImg); } else if (lowKey == 0 && (highKey == VK_UP || highKey == VK_DOWN || highKey == VK_LEFT || highKey == VK_RIGHT)) { OnDirectionKeyDown(highKey); } key = cv::waitKeyEx(0); lowKey = key; highKey = key >> 16; } return 0;}关于OpenCV是怎么实现简单套索工具就分享到这里了，希望以上内容可以对大家有一定的帮助，可以学到更多知识。如果觉得文章不错，可以把它分享出去让更多的人看到。
