How to overlay text on image when working with cv::Mat type

Question

I am using opencv 2.1. In my code I have a few images stored as Mat objects initialized like this:

Mat img1 = imread(\"img/stuff.pgm\", CV_LOAD_IMAGE_GRAYSCA         


        

Answer 1

One nasty detail that I saw into my test code: pay attention into the import stament - it is not displayed into most examples and it needs to be the right import.

My test code used only the putText sample above and I did included the imgproc.h just as I did into some of my oldcode. The code compiled and linked fine however I was facing one weirdy behaviour with the putText (some garbage into my image).

It was a PITA until I figured out that the import was messing up with my social life ...

imageText.cpp

#include "Imaging/imageText.h"
#include "Commons/xLog.h"
#include "opencv2/imgproc.hpp" // << Seems to work right?
using namespace cv;

namespace imaging
{
   inline Mat image2mat( SmartImage image ) NOEXCEPTION
   {
      //TODO: hard coded to work only with CV_8UC3, see the other cases ...
      Mat mat(
         Size( image->WIDTH, image->HEIGHT ),
         CV_8UC3,
         image->buffer,
         Mat::AUTO_STEP
      );

      return mat;
   }

   inline void _writeText_( SmartImage image, const string TEXT )
   {
      Mat mat( image2mat( image ) );

      string text = "Funny text inside the box";
      int fontFace = FONT_HERSHEY_SCRIPT_SIMPLEX;
      double fontScale = 2;
      int thickness = 3;  
      Point textOrg( 10, 130 );
      putText( mat, text, textOrg, fontFace, fontScale, Scalar::all( 255 ), thickness, 8 );
   }

   const bool writeText( SmartImage image, const string text )  NOEXCEPTION
   {
      try
      {
         _writeText_( image, text );
         return true;
      }
      catch( cv::Exception& e )
      {
         LOG_ERROR( "writeText OpenCV ERROR: " << e.what() << "!" );
      }
      catch( ... )
      {
         LOG_ERROR( "writeText ERROR!" );
      }
      return false;
   }
}

Then I just changed the imgproc import above to

#include <opencv2/opencv.hpp> // << It does includes ALL opencv stuff

My 5 cents.