scan_part3

//Detect 4 sided black polygon
ConfigPolygonDetector config = new ConfigPolygonDetector(4, 4);
BinaryPolygonDetector<GrayU8> detector = FactoryShapeDetector.polygon(config, GrayU8.class);

int threshold = GThresholdImageOps.computeOtsu(invert, 0, 255);
GrayU8 binary = new GrayU8(invert.width, invert.height);
ThresholdImageOps.threshold(invert, binary, threshold, true);
detector.process(invert, binary);

FastQueue<Polygon2D_F64> found = detector.getFoundPolygons();

//Go through the found polygons and take the polygon with the largest area. 
//This SHOULD be the page since this should be a picture of a page you are scanning
Polygon2D_F64 polygon = null;
double polygonSize = 0;

for (int i = 0; i < found.size; i++) {

    Polygon2D_F64 poly = found.get(i);

    double size = poly.areaSimple();

    if (size > polygonSize) {
        polygonSize = size;
        polygon = poly;
    }

}

//If unable to identify page... Bail.
if (polygon == null) {
    throw new Exception("Unable to identify page in image");
}