Cimg – The Cool IMAge library – Intro Tutorial

Cimg is a nice and simple image library. What I especially like about it is that it is not fussy and does just what is required – it can load/save many different types of images, provides quite a few very useful built-in functions and provides direct access to individual pixels.

The following piece of code loads lena – the muse of all image computer scientists – seperates the red, green and blue channel and finally saves the red one as lenaRed.png

#include <iostream>

#include "CImg.h"

using namespace cimg_library;

using namespace std;

int main() {

    // Create 4 images - imgLena: a jpg image loaded - imgR, imgG & imgB:

    //                       4 blank images of X, Y, Z, v, fill

    // X-width of image, Y-height of image, Z-depth of image, since 2D Z=1,

    //                       v-number of colours, fill-colours to fill with

    CImg<unsigned char> imgLena("lena.jpg"),

        imgR(128,128,1,3,0),

         imgG(128,128,1,3,0),

         imgB(128,128,1,3,0);

    // for all pixels x,y in imgLena

    cimg_forXY(imgLena,x,y) {

        imgR(x,y,0,0) = imgLena(x,y,0,0),    // Red component of imgLena sent to imgR

        imgG(x,y,0,1) = imgLena(x,y,0,1),    // Green component of imgLena sent to imgG

        imgB(x,y,0,2) = imgLena(x,y,0,2);    // Blue component of imgLena sent to imgB

    }

    // 4 display windows, one for each image

    CImgDisplay main_disp(imgLena,"Original"),

        draw_dispR(imgR,"Red"),

        draw_dispG(imgG,"Green"),

        draw_dispB(imgB,"Blue");

    // wait till window is closed

    while (!main_disp.is_closed){

        main_disp.wait();

        cout << main_disp.mouse_x << "," << main_disp.mouse_y << endl;    // display the coordinates of the mouse  

    }

    imgR.save_png("lenaRed.png");            // saving an image as png

    return 0;

  }

More info is available at http://cimg.sourceforge.net/.