polygon_to_point_distance.cpp

float testApp::distanceFromPoly(const ofPoint & p, const vector<ofPoint> & poly){
    float result = 10000;
    
    // check each line
    for(int i = 0; i < poly.size(); i++){
        int previousIndex = i -1;
        if(previousIndex < 0){
            previousIndex = poly.size() - 1;
        }
        
        ofPoint currentPoint = poly.at(i);
        ofPoint previousPoint = poly.at(previousIndex);
        
        
        float lineLength = sqrt((currentPoint.x - previousPoint.x)*(currentPoint.x - previousPoint.x) + (currentPoint.y - previousPoint.y)*(currentPoint.y - previousPoint.y));
        
        float u = (((p.x - previousPoint.x) * (currentPoint.x - previousPoint.x)) +
                   ((p.y - previousPoint.y) * (currentPoint.y - previousPoint.x))) / (lineLength * lineLength);
        
        //ofVec2f pointVector = ofVec2f(p.x, p.y);
        
        if( u < 0.0f || u > 1.0f )
            continue;
        
        ofVec2f intersection = ofVec2f();
        intersection.x = previousPoint.x + u * (currentPoint.x - previousPoint.x);
        intersection.y = previousPoint.y + u * (currentPoint.y - previousPoint.y);
        

        
        float segmentDistance = intersection.length();
         
        
        if(segmentDistance < result){
            result = segmentDistance;
        }
         
        
        
        
        
    }
    
    return result;
}