Color Palette from image (OpenCV KMeans)

ofApp.cpp

#include "ofApp.h"

//--------------------------------------------------------------
void ofApp::setup(){
    
    video.setDeviceID(0);
    video.setup(320, 240);
}

//--------------------------------------------------------------
void ofApp::update(){
    video.update();
    
    if (video.isFrameNew() && bCapture) {
        
        // copy to src
        cv::Mat src;
        ofxCv::copy(video, src);
        
        // reshape to 1d and convert to 32f
        int total = src.rows * src.cols;
        cv::Mat data = src.reshape(1, total);
        data.convertTo(data, CV_32F);
        
        // run kmeans
        cv::Mat colors;
        std::vector<int> labels;
        cv::kmeans(data, k, labels, cv::TermCriteria(cv::TermCriteria::COUNT + cv::TermCriteria::EPS, 10, 1.0), 3, cv::KmeansFlags::KMEANS_PP_CENTERS, colors);

        // remap color
        for(int i=0; i<total; i++) {
            data.at<float>(i, 0) = colors.at<float>(labels[i], 0);
            data.at<float>(i, 1) = colors.at<float>(labels[i], 1);
            data.at<float>(i, 2) = colors.at<float>(labels[i], 2);
        }
        
        // reshape back
        cv::Mat output = data.reshape(3, src.rows);
        output.convertTo(output, CV_8U);
        
        // copy to ofImage
        ofxCv::copy(output, image);
        image.update();
        
        // update color palette
        palette.clear();
        
        for(int i=0; i<k; i++) {
            auto r = colors.at<float>(i, 0);
            auto g = colors.at<float>(i, 1);
            auto b = colors.at<float>(i, 2);
            palette.push_back(ofColor(r, g, b));
        }
        
        // sort on brightness
        ofSort(palette, [](ofColor &a, ofColor &b) -> bool {
            return a.getBrightness() < b.getBrightness();
        });
        
        bCapture = false;
    }
}

//--------------------------------------------------------------
void ofApp::draw(){

    for(int i=0; i<palette.size(); i++) {
        float x = video.getWidth();
        float y = i * 30;
        ofFill();
        ofSetColor(palette[i]);
        ofDrawRectangle(x, y, 100, 30);
    }
    
    ofSetColor(255);
    video.draw(0, 0);
    image.draw(0, video.getHeight());
    
    ofDrawBitmapStringHighlight("press space to sample "+ofToString(ofGetFrameRate(), 0) + " fps "+ofToString(k)+" colors", 20, ofGetHeight()-20);
}

//--------------------------------------------------------------
void ofApp::keyPressed(int key){
    if (key == OF_KEY_UP) {
        k ++;
    }
    if (key == OF_KEY_DOWN) {
        k --;
        if (k <= 0) k = 1;
    }
    if (key == ' ') {
        bCapture = true;
    }
}

//--------------------------------------------------------------
void ofApp::keyReleased(int key){

}

//--------------------------------------------------------------
void ofApp::mouseMoved(int x, int y ){

}

//--------------------------------------------------------------
void ofApp::mouseDragged(int x, int y, int button){

}

//--------------------------------------------------------------
void ofApp::mousePressed(int x, int y, int button){

}

//--------------------------------------------------------------
void ofApp::mouseReleased(int x, int y, int button){

}

//--------------------------------------------------------------
void ofApp::mouseEntered(int x, int y){

}

//--------------------------------------------------------------
void ofApp::mouseExited(int x, int y){

}

//--------------------------------------------------------------
void ofApp::windowResized(int w, int h){

}

//--------------------------------------------------------------
void ofApp::gotMessage(ofMessage msg){

}

//--------------------------------------------------------------
void ofApp::dragEvent(ofDragInfo dragInfo){ 

}

ofApp.h

#pragma once

#include "ofMain.h"
#include "ofxCv.h"

class ofApp : public ofBaseApp {

	public:
    
    void setup();
    void update();
    void draw();

    void keyPressed(int key);
    void keyReleased(int key);
    void mouseMoved(int x, int y );
    void mouseDragged(int x, int y, int button);
    void mousePressed(int x, int y, int button);
    void mouseReleased(int x, int y, int button);
    void mouseEntered(int x, int y);
    void mouseExited(int x, int y);
    void windowResized(int w, int h);
    void dragEvent(ofDragInfo dragInfo);
    void gotMessage(ofMessage msg);
    
    ofVideoGrabber video;
    ofImage image;
    vector <ofColor> palette;
    
    int k = 8;
    bool bCapture = true;
};