ofColor 로 화소 가지고 놀기. egtColor(), setColor()

void ofApp::mousePressed(int x, int y, int button){
   
    // 채널 정보를 위해
    ofPixels & pixels = img1.getPixels();   // 모든 픽셀 취득
    int numChannels = pixels.getNumChannels();
   
    int w = img1.getWidth();
    int h = img1.getHeight();
   
    ofColor rgb, gray;  // 컬러 변수

    if(numChannels >= 3){
        for (int x=0; x< w ; x++){
            for(int y=0; y< h; y++){
                rgb = img1.getColor(x, y);
                gray=(int)(0.3*rgb.r + 0.6*rgb.g + 0.1*rgb.b);
                //gray= rgb.getBrightness();
                img1.setColor(x, y, gray);
            }
        }// for
    }// if
   
    img1.update();
}