CImg Error : 'gm.exe' is not recognized as an internal or external command,

CImg Error : 'gm.exe' is not recognized as an internal or external command,

I am new to c++ programming , today i was trying to save an image using
CImg . CImg is C++ Template Image Processing Library .
The basic code i wrote is(Please forgive any syntax erros , as copied part
of my codes) :
#include "CImg.h"// Include CImg library header.
#include <iostream>
using namespace cimg_library;
using namespace std;
const int screen_size = 800;
//-------------------------------------------------------------------------------
// Main procedure
//-------------------------------------------------------------------------------
int main()
{
CImg<unsigned char> img(screen_size,screen_size,1,3,20);
CImgDisplay disp(img, "CImg Tutorial");
//Some drawing using img.draw_circle( 10, 10, 60, RED);
img.save("result.jpg"); // save the image
return 0;
}
But I cannot run my program as it says :
Invalid Parameter - 100%
'gm.exe' is not recognized as an internal or external command,
operable program or batch file.
This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.
[CImg] *** CImgIOException *** [instance(800,800,1,3,02150020,non-shared)]
CImg<unsigned char>::save_other() : Failed to save file 'result.jpg'.
Format is not natively supported, and no external commands succeeded.
terminate called after throwing an instance of
'cimg_library::CImgIOException'
what(): [instance(800,800,1,3,02150020,non-shared)] CImg<unsigned
char>::save_other() : Failed to save file 'result.jpg'. Format is not
natively supported, and no external commands succeeded.
Though i can see the image , I cannot save it. After googling a bit i
found people saying to install ImageMagick , i have installed it but no
help . Some of the Forum says to compile against libjpeg, libpng,
libmagick++. I am using Eclipse CDT plugin to write C++ project . Please
help me .