OpenCV4入门教程016：单窗口显示多幅图像

索引地址：系列索引

imshow行数一次只能显示一个Mat对象，一个Mat对象对应一张图片，如果需要显示多张图片，就需要一些操作。最常用的操作是将图片缩小然后利用roi原理移至对应的位置，这样就是在一个Mat中有多个Mat数据，再用imshow显示这一个Mat。

测试代码：

#include <opencv2/opencv.hpp>
#include <iostream>

using namespace cv;

void showManyImages(const std::vector<cv::Mat> &srcImages,
                    cv::Size imgSize)
{
    int nNumImages = srcImages.size();
    cv::Size nSizeWindows;
    if (nNumImages > 12)
    {
        std::cout << " Not more than 12 images!" << std::endl;
        return;
    }
    // 根据图片序列数量来确定分割小窗口形态
    switch (nNumImages)
    {
    case 1:
        nSizeWindows = cv::Size(1, 1);
        break;
    case 2:
        nSizeWindows = cv::Size(2, 1);
        break;
    case 3:
    case 4:
        nSizeWindows = cv::Size(2, 2);
        break;
    case 5:
    case 6:
        nSizeWindows = cv::Size(3, 2);
        break;
    case 7:
    case 8:
        nSizeWindows = cv::Size(4, 2);
        break;
    case 9:
        nSizeWindows = cv::Size(3, 3);
        break;
    default:
        nSizeWindows = cv::Size(4, 3);
        break;
    }
    // 设置小图像尺寸，间隙，边界
    int nShowImageSize = 200;
    int nSplitLineSize = 15;
    int nAroundLineSize = 50;
    // 创建输出图像，图像大小根据输入源确定
    const int imagesHeight = nShowImageSize * nSizeWindows.width +
                             nAroundLineSize + (nSizeWindows.width - 1) * nSplitLineSize;
    const int imagesWidth = nShowImageSize * nSizeWindows.height +
                            nAroundLineSize + (nSizeWindows.height - 1) * nSplitLineSize;
    std::cout << imagesWidth << " " << imagesHeight << std::endl;
    cv::Mat showWindowImages(imagesWidth, imagesHeight,
                             CV_8UC3, cv::Scalar(0, 0, 0));
    // 提取对应小图像的左上角坐标X，Y
    int posX = (showWindowImages.cols - (nShowImageSize *
                                             nSizeWindows.width +
                                         (nSizeWindows.width - 1) *
                                             nSplitLineSize)) /
               2;
    int posY = (showWindowImages.rows - (nShowImageSize *
                                             nSizeWindows.height +
                                         (nSizeWindows.height - 1) *
                                             nSplitLineSize)) /
               2;
    std::cout << posX << " " << posY << std::endl;
    int tempPosX = posX;
    int tempPosY = posY;
    // 将每一小幅图像整合大图像
    for (int i = 0; i < nNumImages; i++)
    {
        // 小图像坐标转换
        if ((i % nSizeWindows.width == 0) && (tempPosX != posX))
        {
            tempPosX = posX;
            tempPosY += (nSplitLineSize + nShowImageSize);
        }
        // 利用Rect区域将小图像置于大图像相应区域
        cv::Mat tempImage = showWindowImages(cv::Rect(tempPosX,
                                                      tempPosY, nShowImageSize, nShowImageSize));
        // 利用resize函数实现图像缩放
        resize(srcImages[i], tempImage,
               cv::Size(nShowImageSize, nShowImageSize));
        tempPosX += (nSplitLineSize + nShowImageSize);
    }
    cv::imshow("show Images", showWindowImages);
    imwrite("result.jpg",showWindowImages);
}

int main()
{
    // 图像源输入
    std::vector<cv::Mat> srcImages(9);
    srcImages[0] = cv::imread("lenna.jpg");
    srcImages[1] = cv::imread("lenna.jpg");
    srcImages[2] = cv::imread("lenna.jpg");
    srcImages[3] = cv::imread("lenna.jpg");
    srcImages[4] = cv::imread("lenna.jpg");
    srcImages[5] = cv::imread("lenna.jpg");
    srcImages[6] = cv::imread("lenna.jpg");
    srcImages[7] = cv::imread("lenna.jpg");
    srcImages[8] = cv::imread("lenna.jpg");
    // 判断当前vector读入的正确性
    for (int i = 0; i < srcImages.size(); i++)
    {
        if (!srcImages[i].data)
        {
            std::cout << "read error!" << std::endl;
            return -1;
        }
    }
    // 调用单窗口显示图像
    showManyImages(srcImages, cv::Size(512, 400));
    cv::waitKey(0);
    return 0;
}

运行结果：