Implemented Contour Finding

Before contours can be found, video is converted to grayscale,
background subtraction is performed and results get binarized.

Circles are characterized by the aspect ratio of the individual blob.

beerpong/bin/data/README.txt

+Video mit FFMPEG verkleinern:
+
+ffmpeg -i beer.mkv -s 568x320 -c:a copy shrink.mkv 

beerpong/src/ofApp.cpp

 #include "ofApp.h"
 
+#define VIDEO_WIDTH 568
+#define VIDEO_HEIGHT 320
+
 //--------------------------------------------------------------
 void ofApp::setup(){
+	vidPlayer.load("beer.mkv"); // in /bin/data/
+	vidPlayer.play();
+	vidPlayer.setLoopState(OF_LOOP_NORMAL);
+
+	colorVideo.allocate(VIDEO_WIDTH, VIDEO_HEIGHT);
+	grayVideo.allocate(VIDEO_WIDTH, VIDEO_HEIGHT);
 
+	learnBackground = true;
+	threshhold = 80;
 }
 
 //--------------------------------------------------------------
 void ofApp::update(){
 
+	vidPlayer.update();
+	colorVideo.setFromPixels(vidPlayer.getPixels());
+
+	grayVideo = colorVideo; // Convert Color to Grayscale
+
+	if (learnBackground){
+		background = grayVideo;
+		learnBackground = false;
+	}
+
+	// Background subtraction
+	binarized.absDiff(background, grayVideo);
+	// Binarization
+	binarized.threshold(threshhold);
+
+	contourFinder.findContours(
+		binarized,
+		10,
+		VIDEO_HEIGHT * VIDEO_WIDTH / 10,
+		10,
+		true);
 }
 
 //--------------------------------------------------------------
 void ofApp::draw(){
-
+	ofSetHexColor(0xffffff);
+	colorVideo.draw(20, 20);
+	grayVideo.draw(40 + VIDEO_WIDTH, 20);
+	background.draw(20, 40 + VIDEO_HEIGHT);
+	binarized.draw(40 + VIDEO_WIDTH, 40 + VIDEO_HEIGHT);
+
+	ofFill();
+	ofSetHexColor(0x333333);
+	ofDrawRectangle(40 + VIDEO_WIDTH, 60 + VIDEO_HEIGHT + VIDEO_HEIGHT, VIDEO_WIDTH, VIDEO_HEIGHT);
+	ofSetHexColor(0xffffff);
+
+	for (int i = 0; i < contourFinder.blobs.size(); i++) {
+		ofxCvBlob blob = contourFinder.blobs[i];
+		
+
+		// draw over the centroid if the blob is a hole
+		ofSetColor(255);
+
+		// https://docs.opencv.org/master/d1/d32/tutorial_py_contour_properties.html
+		float aspect_ratio = blob.boundingRect.getWidth() / blob.boundingRect.getHeight();
+
+		stringstream sizeStr;
+		sizeStr << std::to_string(i) << ": " << std::to_string(contourFinder.blobs[i].area);
+		sizeStr << " | F=" << aspect_ratio;
+
+
+		if (aspect_ratio > 0.5 && aspect_ratio < 1.5)
+		{
+			blob.draw(40 + VIDEO_WIDTH, 60 + VIDEO_HEIGHT + VIDEO_HEIGHT);
+			ofDrawBitmapString(sizeStr.str(),
+				contourFinder.blobs[i].boundingRect.getCenter().x + 40 + VIDEO_WIDTH,
+				contourFinder.blobs[i].boundingRect.getCenter().y + 60 + VIDEO_HEIGHT + VIDEO_HEIGHT);
+		}
+	}
 }
 
 //--------------------------------------------------------------
 void ofApp::keyPressed(int key){
-
+	if (key == '-') threshhold--;
+	else if (key == '+') threshhold++;
+	else if (key == ' ') learnBackground = true;
+	else if (key == '0') vidPlayer.setPaused(!vidPlayer.isPaused());
+	else if (key == OF_KEY_RIGHT) vidPlayer.nextFrame();
+	else if (key == OF_KEY_LEFT) vidPlayer.previousFrame();
+	else;
 }
 
 //--------------------------------------------------------------

beerpong/src/ofApp.h

 #pragma once
 
 #include "ofMain.h"
+#include "ofxOpenCv.h"
 
 class ofApp : public ofBaseApp{
 
 		void dragEvent(ofDragInfo dragInfo);
 		void gotMessage(ofMessage msg);
 		
+		ofVideoPlayer vidPlayer;
+
+		// Images displaying original video
+		ofxCvColorImage colorVideo;
+		ofxCvGrayscaleImage grayVideo;
+
+		ofxCvGrayscaleImage background;
+		ofxCvGrayscaleImage binarized;
+
+		ofxCvContourFinder 	contourFinder;
+
+		bool learnBackground;
+		int threshhold;
 };