OpenCV: Pseudo Coloring

Download the Project folder and the source code [2.62 Mb].



**UPDATE**
Please Change the Code from:

ptr_d[3*x] = (int) (temp * 255/180);

to

ptr_d[3*x] = (int) (temp * 255/60);
in line 108, as show below. This improves the upper end of thermal image.

Sample Code:

//______________________________________________________________________________________
// OpenCV Pseudo Coloring of Images
// Author: Bharath Prabhuswamy
//______________________________________________________________________________________
//______________________________________________________________________________________

#include "cv.h"
#include "highgui.h"
#include <stdio.h>
#include <math.h>

int main()
{
        IplImage* img  = cvLoadImage("thermal.jpg");
 int flag;
 
 /* Always check if the program can find a file */
 if( !img ) 
   return -1;

 IplImage* gray = cvCreateImage( cvGetSize(img), 8, 1 );
 IplImage* disp = cvCreateImage( cvGetSize(img), 8, 3 );
 cvZero(disp);

 /*Convert the image to gray*/
 cvCvtColor(img,gray,CV_RGB2GRAY);

 uchar* ptr_d;
 uchar* ptr_g;
 int temp;

 printf("Select an option for Colouring -\n");
 printf("1.MRI Scan\n");
 printf("2.Thermal Image\n");
 scanf("%d",&flag);

 /*Check if the user selects a valid option */
 if(flag !=1 && flag !=2)
 {
  printf("Invalid Input\n");
  printf("Application Exit\n");
  return -1;
 }
  
 for( int y=0; y<gray->height; y++) 
 {
  ptr_g = (uchar*) (gray->imageData + y * gray->widthStep);
  ptr_d = (uchar*) (disp->imageData + y * disp->widthStep);
   
  for(int x=0; x<img->width; x++ ) 
  {
   /*The option is MRI */
   if(flag ==1)
   {
 //Colour pixels that Black and fade to Blue
    if(ptr_g[x] < 25)                          
    {
     temp = ptr_g[x];
     ptr_d[3*x+2] = 0;
     ptr_d[3*x+1] = 0;
     ptr_d[3*x] = (int) (temp * 255/25);
    }
    else
    {
     temp = ptr_g[x] - 25;
//Colour pixels that nearly Grey to Blue and then fade to Green 
     if(temp >=0 && temp < 115)     
                                        //
     {
      ptr_d[3*x+1] = (int) (temp * 255/115);
      ptr_d[3*x] = 255 -(int) (temp * 255/115);
     }
//Starting From Green,Colour pixels that nearly White to Red 
     else if(temp >=116 && temp <= 230)   
     {
      temp = ptr_g[x] - 115;
      ptr_d[3*x+2] = (int) (temp * 255/115);
      ptr_d[3*x+1] = 255 -(int) (temp * 255/115);
     }
    }
   }
   else
   {
//Colour pixels that Black and fade to Purple
    if(ptr_g[x] < 15)      
    {
     temp = ptr_g[x];
     ptr_d[3*x+2] = (int)(temp * 90/15);
     ptr_d[3*x+1] = 0;
     ptr_d[3*x] = (int)(temp * 90/15);
    }
    else
    {
     temp = ptr_g[x] - 15;
//Colour pixels that nearly Grey to Purple and fade to Yellow
     if(temp >=0 && temp < 180)   
     {
      ptr_d[3*x+2] = (int)(90 + (temp * 155/180));
      ptr_d[3*x+1] = (int)(temp * 255/180);
      ptr_d[3*x] = (int)(90 - (temp * 90/180));
     }
//Starting From Yellow,Colour pixels that nearly White to White itself 
     else if(temp >=180 && temp <= 240) 
     {
      temp = ptr_g[x] - 180;
      ptr_d[3*x+2] = 255;
      ptr_d[3*x+1] = 255;
      ptr_d[3*x] = (int) (temp * 255/60);
     }
    }

   }
  }
  
 }

 /* create a window to show the coloured image */
 cvNamedWindow( "Display", 1 );
 cvShowImage( "Display",disp);
 
 /* Save the coloured image if needed*/
 //cvSaveImage("output.jpg",disp);
 cvWaitKey(0);

 cvDestroyWindow( "Display" );
    cvReleaseImage( &img );

    return 0;
}

Images: