学更好的别人，

做更好的自己。

——《微卡智享》

本文长度为2796字，预计阅读7分钟

前言

以前的文章《C++ OpenCV视频操作之图像输出文字》介绍了OpenCV中的putText函数可以输出文字，但是这个函数只能输出英文，如果输入的是中文会变为乱码，今天我们就来实现OpenCV输出中文（只在windows环境下）。

核心代码

微卡智享

建一个putText的类，里面的putTextZH设置为静态方法

putText.h

#pragma once
#ifndef PUTTEXT_H_
#define PUTTEXT_H_


#include <Windows.h>
#include <string>
#include <opencv2/opencv.hpp>


using namespace cv;


class putText
{
private:
  static void GetStringSize(HDC hdc, const char* str, int* w, int* h);


public:
  static void putTextZH(Mat& dst, const char* str, Point org, Scalar color, int fontsize,
    const char* fn = "Arial", bool italic = false, bool underline = false);
};


#endif // !PUTTEXT_H_

putText.cpp

#include "putText.h"


void putText::GetStringSize(HDC hdc, const char* str, int* w, int* h)
{
  SIZE size;
  GetTextExtentPoint32A(hdc, str, strlen(str), &size);
  if (w != 0) *w = size.cx;
  if (h != 0) *h = size.cy;
}


void putText::putTextZH(Mat& dst, const char* str, Point org, Scalar color, int fontsize, const char* fn, bool italic, bool underline)
{
  CV_Assert(dst.data != 0 && (dst.channels() == 1 || dst.channels() == 3));


  int x, y, r, b;
  //坐标点大于图像宽和高直接返回
  if (org.x > dst.cols || org.y > dst.rows) return;
  x = org.x < 0 ? -org.x : 0;
  y = org.y < 0 ? -org.y : 0;


  LOGFONTA lf;
  lf.lfHeight = -fontsize; //字体高度
  lf.lfWidth = 0;          //平均宽度
  lf.lfEscapement = 0;   //字符排列角度
  lf.lfOrientation = 0;   //字符本身旋转的角度
  lf.lfWeight = 5;        //设置字体线条的宽度
  lf.lfItalic = italic; //斜体
  lf.lfUnderline = underline; //下划线
  lf.lfStrikeOut = 0;     //是否字符中央加横线
  lf.lfCharSet = DEFAULT_CHARSET;   //字符集
  lf.lfOutPrecision = 0;  //字体的精确度
  lf.lfQuality = PROOF_QUALITY;  //字体质量
  lf.lfPitchAndFamily = 0; //选择字体的间距和字体家族
  strcpy_s(lf.lfFaceName, fn); //字体的名称


  HFONT hf = CreateFontIndirectA(&lf);
  HDC hdc = CreateCompatibleDC(0);
  HFONT holdfont = (HFONT)SelectObject(hdc, hf);


  int strBaseW = 0, strBaseH = 0;
  int singleRow = 0;
  char buf[1 << 12];
  strcpy_s(buf, str);
  char* bufT[1 << 12];   //这个用于分隔字符串后剩余的字符，可能会超出。


  //处理多行
    {
        int nnh = 0;
        int cw, ch;


        const char* ln = strtok_s(buf, "\n", bufT);
        while (ln != 0)
        {
            GetStringSize(hdc, ln, &cw, &ch);
            strBaseW = max(strBaseW, cw);
            strBaseH = max(strBaseH, ch);


            ln = strtok_s(0, "\n", bufT);
            nnh++;
        }
        singleRow = strBaseH;
        strBaseH *= nnh;
    }


    if (org.x + strBaseW < 0 || org.y + strBaseH < 0)
    {
        SelectObject(hdc, holdfont);
        DeleteObject(hf);
        DeleteObject(hdc);
        return;
    }


    r = org.x + strBaseW > dst.cols ? dst.cols - org.x - 1 : strBaseW - 1;
    b = org.y + strBaseH > dst.rows ? dst.rows - org.y - 1 : strBaseH - 1;
    org.x = org.x < 0 ? 0 : org.x;
    org.y = org.y < 0 ? 0 : org.y;


    BITMAPINFO bmp = { 0 };
    BITMAPINFOHEADER& bih = bmp.bmiHeader;
    int strDrawLineStep = strBaseW * 3 % 4 == 0 ? strBaseW * 3 : (strBaseW * 3 + 4 - ((strBaseW * 3) % 4));


    bih.biSize = sizeof(BITMAPINFOHEADER);
    bih.biWidth = strBaseW;
    bih.biHeight = strBaseH;
    bih.biPlanes = 1;
    bih.biBitCount = 24;
    bih.biCompression = BI_RGB;
    bih.biSizeImage = strBaseH * strDrawLineStep;
    bih.biClrUsed = 0;
    bih.biClrImportant = 0;


    void* pDibData = 0;
    HBITMAP hBmp = CreateDIBSection(hdc, &bmp, DIB_RGB_COLORS, &pDibData, 0, 0);


    CV_Assert(pDibData != 0);
    HBITMAP hOldBmp = (HBITMAP)SelectObject(hdc, hBmp);


    //color.val[2], color.val[1], color.val[0]
    SetTextColor(hdc, RGB(255, 255, 255));
    SetBkColor(hdc, 0);
    //SetStretchBltMode(hDC, COLORONCOLOR);


    strcpy_s(buf, str);
    const char* ln = strtok_s(buf, "\n", bufT);
    int outTextY = 0;
    while (ln != 0)
    {
        TextOutA(hdc, 0, outTextY, ln, strlen(ln));
        outTextY += singleRow;
        ln = strtok_s(0, "\n", bufT);
    }
    uchar* dstData = (uchar*)dst.data;
    int dstStep = dst.step / sizeof(dstData[0]);
    unsigned char* pImg = (unsigned char*)dst.data + org.x * dst.channels() + org.y * dstStep;
    unsigned char* pStr = (unsigned char*)pDibData + x * 3;
    for (int tty = y; tty <= b; ++tty)
    {
        unsigned char* subImg = pImg + (tty - y) * dstStep;
        unsigned char* subStr = pStr + (strBaseH - tty - 1) * strDrawLineStep;
        for (int ttx = x; ttx <= r; ++ttx)
        {
            for (int n = 0; n < dst.channels(); ++n) {
                double vtxt = subStr[n] / 255.0;
                int cvv = vtxt * color.val[n] + (1 - vtxt) * subImg[n];
                subImg[n] = cvv > 255 ? 255 : (cvv < 0 ? 0 : cvv);
            }


            subStr += 3;
            subImg += dst.channels();
        }
    }


    SelectObject(hdc, hOldBmp);
    SelectObject(hdc, holdfont);
    DeleteObject(hf);
    DeleteObject(hBmp);
    DeleteDC(hdc);
}

调用方式

    //输出中文显示
    putText::putTextZH(src, "我是Vaccae,请关注微卡智享", Point(rect.x-40, rect.y-23),
      Scalar(0, 0, 255), 20, "微软雅黑");

代码演示

微卡智享

新建一个opencvputtextzh的项目，配置参见《VS2017配置OpenCV通用属性》。

上图中的putText.h和putText.cpp就是上面的核心代码，接下来我们看一下main的代码。

main.cpp

#include <iostream>
#include <opencv2/opencv.hpp>
#include "putText.h"


using namespace std;
using namespace cv;


int main(int argc, char** argv) {


  Mat src = imread("E:/DCIM/test3.jpg");
  if (!src.data) {
    cout << "could not find src" << endl;
    return -1;
  }


  Mat tmpsrc, dst;
  //转为灰度图
  cvtColor(src, tmpsrc, COLOR_BGR2GRAY);
  //二值化
  threshold(tmpsrc, tmpsrc, 0, 255, THRESH_BINARY_INV | THRESH_OTSU);
  //发现轮廓
  vector<vector<Point>> contours;
  findContours(tmpsrc, contours, RETR_EXTERNAL, CHAIN_APPROX_SIMPLE);


  //用于存放拆线点集
  vector<vector<Point>> contours_poly(contours.size());


  for (int i=0; i < contours.size(); ++i) {
    //将多边形进行拟合
    approxPolyDP(Mat(contours[i]), contours_poly[i], 3, true);


    //获取矩形并在源图上画出来
    Rect rect = boundingRect(contours_poly[i]);
    rectangle(src, rect, Scalar(0, 0, 255));


    //输出中文显示
    putText::putTextZH(src, "我是Vaccae,请关注微卡智享", Point(rect.x-40, rect.y-23),
      Scalar(0, 0, 255), 20, "微软雅黑");
  }


  imshow("src", src);


  waitKey(0);
  return 0;
}

实现效果

完

扫描二维码

获取更多精彩

微卡智享

「 往期文章 」

C++ OpenCV标记函数drawMarker的使用

Unity3D使用Timeline实现过场动画

Unity3D中使用Joystick Pack实现摇杆控制