在OpenCV图像上面写很小的字符？

Question

所以我试图在图像上使用putText（）来编写单个字符以适应25x25的框但文本太小而无法渲染，它看起来就像我选择文本的任何颜色的blob 。有没有办法用OpenCV创建小的，可读的文本覆盖到图像上？

Answer 1

以下是使用putText()同时加载Photoshop或GIMP中创建的文件中的字符的示例。

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

using namespace cv;
using namespace std;

int
main(int argc,char*argv[])
{
   // Make a 3 channel image
   cv::Mat main(200,300,CV_8UC3);

   // Fill entire image with magenta
   main = cv::Scalar(255,0,255);

   // Load a character "M" from a file and overlay
   Mat txt = cv::imread("M.png",-CV_LOAD_IMAGE_ANYDEPTH);
   txt.copyTo(main(cv::Rect(80,120,txt.cols,txt.rows)));

   // Now use puttext() to do a white S
   int fontFace = FONT_HERSHEY_COMPLEX_SMALL;
   double fontScale=1.5;
   string text="S";
   putText(main,"S",Point(60,100),fontFace,fontScale,Scalar(255,255,255));

   // Save to disk
   imwrite("result.png",main);
}

这里是M.png文件：

结果如下：

我还注意到反锯齿字体（在下图中的右侧）看起来有点容易阅读：

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

using namespace cv;
using namespace std;

int
main(int argc,char*argv[])
{
   // Make a 3 channel image
   cv::Mat main(280,800,CV_8UC3);

   // Fill entire image with magenta
   main = cv::Scalar(255,0,255);

   double fontScale=1.5;
   int thickness=1;
   int x=10,y=40;
   putText(main,"Simplex",Point(x,y),CV_FONT_HERSHEY_SIMPLEX,fontScale,Scalar(255,255,255),thickness,8);
   putText(main,"Simplex AA",Point(x+400,y),CV_FONT_HERSHEY_SIMPLEX,fontScale,Scalar(255,255,255),thickness,CV_AA);
   y+=40;
   putText(main,"Plain",Point(x,y),CV_FONT_HERSHEY_PLAIN,fontScale,Scalar(255,255,255),thickness,8);
   putText(main,"Plain AA",Point(x+400,y),CV_FONT_HERSHEY_PLAIN,fontScale,Scalar(255,255,255),thickness,CV_AA);
   y+=40;
   putText(main,"Duplex",Point(x,y),CV_FONT_HERSHEY_DUPLEX,fontScale,Scalar(255,255,255),thickness,8);
   putText(main,"Duplex AA",Point(x+400,y),CV_FONT_HERSHEY_DUPLEX,fontScale,Scalar(255,255,255),thickness,CV_AA);
   y+=40;
   putText(main,"Complex",Point(x,y),CV_FONT_HERSHEY_COMPLEX,fontScale,Scalar(255,255,255),thickness,8);
   putText(main,"Complex AA",Point(x+400,y),CV_FONT_HERSHEY_COMPLEX,fontScale,Scalar(255,255,255),thickness,CV_AA);
   y+=40;
   putText(main,"Triplex",Point(x,y),CV_FONT_HERSHEY_TRIPLEX,fontScale,Scalar(255,255,255),thickness,8);
   putText(main,"Triplex AA",Point(x+400,y),CV_FONT_HERSHEY_TRIPLEX,fontScale,Scalar(255,255,255),thickness,CV_AA);
   y+=40;
   putText(main,"Script",Point(x,y),CV_FONT_HERSHEY_SCRIPT_SIMPLEX,fontScale,Scalar(255,255,255),thickness,8);
   putText(main,"Script AA",Point(x+400,y),CV_FONT_HERSHEY_SCRIPT_SIMPLEX,fontScale,Scalar(255,255,255),thickness,CV_AA);

   // Save to disk
   imwrite("result.png",main);
}