OpenCV——字符提取并保存

截取图中上方数码管中的数字

基本思路：

1、将图像转化为灰度图

2、截取ROI区域

3、二值化

4、循环遍历每一行和每一列，得到字符的坐标

5、截取并保存

#include <opencv2/opencv.hpp>
#include <iostream>
#include <math.h>
#include <stdio.h>

using namespace cv;
using namespace std;


int getColSum(Mat& src, int t);
int getRowSum(Mat& src, int t);
void cutLeft(Mat& src, Mat& leftImg, Mat& rightImg);
void cutTop(Mat& src, Mat& dstImg);

int main()
{
    Mat src = imread("数字.jpg", 0);
    threshold(src, src, 0, 255, THRESH_BINARY|THRESH_OTSU);
    imshow("origin", src);

    
    
    Mat roi = src(Rect(250, 25, src.cols-350, 300));//截取ROI区域
    imshow("ROI", roi);
    //形态学操作去除干扰
    Mat kernel = getStructuringElement(MORPH_RECT, Size(7, 7), Point(-1, -1));
    morphologyEx(roi, roi, MORPH_OPEN, kernel);

    Mat kernel2 = getStructuringElement(MORPH_RECT, Size(7,7), Point(-1, -1));
    dilate(roi, roi, kernel2);
    imshow("ROI", roi);

    Mat leftImg, rightImg;
        
    rightImg = roi.clone();
    string nameLeft[5] = {"digital_1.jpg","digital_2.jpg" ,"digital_3.jpg" ,"digital_4.jpg" ,"digital_5.jpg" };
    for (int i = 0; i < 5; i++) {

        cutLeft(rightImg, leftImg, rightImg);        
        imwrite(nameLeft[i], leftImg);//保存
    }

    

    waitKey(0);
    return 0;
}
//函数作用：计算某一列的像素和
//输入为二值图像
int getColSum(Mat& src, int t) {
    int rowNumber = src.rows;//行数
    int colNumber = src.cols;//列数
    uchar ColSum = 0;
    for (int i = 0; i < rowNumber; i++)
    {
        for (int j = 0; j < colNumber; j++)
        {
            if (j == t) 
            {

                ColSum += src.at<uchar>(i, j);
            }

        }
    }
    return ColSum;
}

int getRowSum(Mat& src, int t) {
    int rowNumber = src.rows;//行数
    int colNumber = src.cols;//列数
    uchar RowSum = 0;
    for (int i = 0; i < rowNumber; i++)
    {
        if (i== t)
        {

            for (int j = 0; j < colNumber; j++)
            {

                RowSum += src.at<uchar>(i, j);


            }
        }
    }
    return RowSum;
}
void cutLeft(Mat& src, Mat& leftImg, Mat& rightImg)//左右切割
{
    int left, right;
    left = 0;
    right = src.cols;

    //循环遍历每一列，记录下左端的坐标
    int i;
    for (i = 0; i < src.cols; i++)
    {
        int colValue = getColSum(src, i);
        //cout <<i<<" th "<< colValue << endl;
        if (colValue > 0)
        {
            left = i;
            break;
        }
    }    

    //接着循环遍历每一列，记录下右端的坐标
    for (; i < src.cols; i++)
    {
        int colValue = getColSum(src, i);
        //cout << i << " th " << colValue << endl;
        if (colValue == 0)
        {
            right = i;
            break;
        }
    }

    
    int width = right - left;//计算字符的宽度

    Rect rect(left, 0, width, src.rows);
    leftImg = src(rect);
    Rect rectRight(right, 0, src.cols - right, src.rows);
    rightImg = src(rectRight);
    cutTop(leftImg, leftImg);
    
}

void cutTop(Mat& src, Mat& dstImg)//上下切割
{
    int top, bottom;
    top = 0;
    bottom = src.rows;

    int i;
    for (i = 0; i < src.rows; i++)
    {
        int colValue = getRowSum(src, i);
        //cout <<i<<" th "<< colValue << endl;
        if (colValue > 0)
        {
            top = i;
            break;
        }
    }
    for (; i < src.rows; i++)
    {
        int colValue = getRowSum(src, i);
        //cout << i << " th " << colValue << endl;
        if (colValue == 0)
        {
            bottom = i;
            break;
        }
    }

    int height = bottom - top;
    Rect rect(0, top, src.cols, height);
    dstImg = src(rect);
}