如何使用CImg库显示临时图像

Question

I was wondering if someone can help me with this... I need to display my image for 15 seconds and i also have to use the draw_text function to display on the image some details with int value, and it asks for const char*const text value. I am not supposed to add libraries, just the iostream and of course CImg.

this is the current code i've been trying to use.

CImg<unsigned char> image(filename);
 unsigned char red[] = { 255,0,0 };
 unsigned char blue[] = { 0,0,255 };
 image.draw_text(5,5,"Here i want to call the int value",red,blue,1,10);
 if (opcion == 0x33)
 {
     //Here i want to display the following line for 15 seconds
     image.display("hello world");
 }

Answer 1

I am not sure whether your question is about getting an integer into a string, or about displaying an image for 15 seconds. However, the following code should show you a way of doing both.

The main thing is that the main loop waits up to 100ms for events, and if you do that 150 times, your screen will display for around 15 seconds.

#include <iostream>
#include "CImg.h"
using namespace std;
using namespace cimg_library;

#define BUFSIZE 128

int main(int argc, char** const argv)
{
   // Create empty yellow image
   CImg<unsigned char> image(256,256,1,3);
   cimg_forXY(image,x,y) { image(x,y,0,0)=255; image(x,y,0,1)=255; image(x,y,0,2)=0; }

   unsigned char red[]  = { 255,0,0 };
   unsigned char blue[] = { 0,0,255 };
   char text[BUFSIZE];

   int someInt=42;
   snprintf(text,BUFSIZE,"Hello, the integer is %d",someInt);

   image.draw_text(5,5,text,red,blue,1,10);
   CImgDisplay main_disp(image,"Hello world");

   // Loop 150 times @100ms each
   for(int i=0;i<150;i++){
      if(main_disp.is_closed()){break;}
      main_disp.wait(100);
   }
}

There are other, more C++, ways of getting an integer into a string, but this method will get you started.

The method of running 15 seconds is also quite crude, but I suspect it is only a nominal 15 seconds you want. You could get the time at the start of the program, using time() and then get the time again on each pass through the loop and break if the difference exceeds 15 - but that is a little less clear than the simple method above. That code could look like this:

#include <iostream>
#include <ctime>
#include "CImg.h"
using namespace std;
using namespace cimg_library;

#define BUFSIZE 128

int main(int argc, char** const argv)
{
   // Create empty yellow image
   CImg<unsigned char> image(256,256,1,3);
   cimg_forXY(image,x,y) { image(x,y,0,0)=255; image(x,y,0,1)=255; image(x,y,0,2)=0; }

   unsigned char red[]  = { 255,0,0 };
   unsigned char blue[] = { 0,0,255 };
   char text[BUFSIZE];

   int someInt=42;
   snprintf(text,BUFSIZE,"Hello, the integer is %d",someInt);

   image.draw_text(5,5,text,red,blue,1,10);
   CImgDisplay main_disp(image,"Hello world");

   time_t start,diff;
   start=time(NULL);

   // Loop till display closed or 15 seconds elapsed
   while(1){
      // Exit if closed
      if(main_disp.is_closed()){break;}

      // Exit if 15 seconds are up
      diff=time(NULL)-start;
      if(diff>15){break;}

      main_disp.wait(10);
   }
}

You can do the string stuff in a more C++ way like this:

#include <iostream>
#include <sstream>
#include <ctime>
#include <string>
#include "CImg.h"
using namespace std;
using namespace cimg_library;

int main(int argc, char** const argv)
{
   // Create empty yellow image
   CImg<unsigned char> image(256,256,1,3);
   cimg_forXY(image,x,y) { image(x,y,0,0)=255; image(x,y,0,1)=255; image(x,y,0,2)=0; }

   unsigned char red[]  = { 255,0,0 };
   unsigned char blue[] = { 0,0,255 };

   int someInt=42;
   string text="The integer is: ";
   text += to_string(someInt);

   image.draw_text(5,5,text.c_str(),red,blue,1,10);
   CImgDisplay main_disp(image,"Hello world");

   time_t start,diff;
   start=time(NULL);

   // Loop till display closed or 15 seconds elapsed
   while(1){
      // Exit if closed
      if(main_disp.is_closed()){break;}

      // Exit if 15 seconds are up
      diff=time(NULL)-start;
      if(diff>15){break;}

      main_disp.wait(10);
   }
}