We Keep Coding

How to more realistically simulate light on a sphere?

I am attempting to simulate a sphere, and shade it realistically given an origin vector for the light, and the sphere being centered around the origin. Moreover, the light's vector is the normal vector on a larger invisible sphere at a chosen point. The sphere looks off.
https://imgur.com/a/IDIwQQF
The problem, is that it is very difficult to bug fix this kind of program. Especially considering that I know how I want it to look in my head, but when looking at the numbers in my program there is very little meaning attached to them.
Since I don't know where the issue is, I'm forced to paste all of it here.
public class SphereDrawing extends JPanel {
private static final long serialVersionUID = 1L;
private static final int ADJ = 320;
private static final double LIGHT_SPHERE_RADIUS = 5;
private static final double LIGHT_X = 3;
private static final double LIGHT_Y = 4;
private static final double LIGHT_Z = 0;
private static final double DRAWN_SPHERE_RADIUS = 1;
private static final int POINT_COUNT = 1000000;
private static Coord[] points;
private static final double SCALE = 200;
public SphereDrawing() {
setPreferredSize(new Dimension(640, 640));
setBackground(Color.white);
points = new Coord[POINT_COUNT];
initializePoints();
for (int i = 0; i < points.length; i++) {
points[i].scale();
}
new Timer(17, (ActionEvent e) -> {
repaint();
}).start();
}
public void initializePoints() { //finding the points on the surface of the sphere (hopefully somewhat equidistant)
double random = Math.random() * (double)POINT_COUNT;
double offset = 2/(double)POINT_COUNT;
double increment = Math.PI * (3 - Math.sqrt(5));
for (int i = 0; i < POINT_COUNT; i++) {
double y = ((i * offset) - 1) + (offset / 2);
double r = Math.sqrt(1 - Math.pow(y, 2));
double phi = ((i + random) % (double)POINT_COUNT) * increment;
double x = Math.cos(phi) * r;
double z = Math.sin(phi) * r;
points[i] = new Coord(x, y, z);
}
}
public void drawSphere(Graphics2D g) {
g.translate(ADJ, ADJ); //shifting from origin for drawing purposes
Arrays.sort(points); //sorting points by their z coordinates
double iHat = -2 * LIGHT_X;
double jHat = -2 * LIGHT_Y; //Light vector
double kHat = -2 * LIGHT_Z;
double angL1 = 0;
if (Math.abs(iHat) != 0.0)
angL1 = Math.atan(jHat / iHat); //converting light vector to spherical coordinates
else
angL1 = Math.PI/2;
double angL2 = Math.atan(Math.sqrt(Math.pow(iHat, 2) + Math.pow(jHat, 2))/ kHat);
double maxArcLength = LIGHT_SPHERE_RADIUS * Math.PI; // maximum arc length
for (int i = 0; i < points.length; i++) {
if(points[i].checkValid()) {
double siHat = -2 * points[i].x;
double sjHat = -2 * points[i].y; //finding normal vector for the given point on the sphere
double skHat = -2 * points[i].z;
double angSF1 = -1 * Math.abs(Math.atan(sjHat / siHat)); // converting vector to spherical coordinates
double angSF2 = Math.atan(Math.sqrt(Math.pow(siHat, 2) + Math.pow(sjHat, 2))/ skHat);
double actArcLength = LIGHT_SPHERE_RADIUS * Math.acos(Math.cos(angL1) * Math.cos(angSF1) + Math.sin(angL1) * Math.sin(angSF1) * Math.cos(angL2 - angSF2)); //calculating arc length at this point
double comp = actArcLength / maxArcLength; // comparing the maximum arc length to the calculated arc length for this vector
int col = (int)(comp * 255);
col = Math.abs(col);
g.setColor(new Color(col, col, col));
double ovalDim = (4 * Math.PI * Math.pow(DRAWN_SPHERE_RADIUS, 2))/POINT_COUNT; //using surface area to determine how large size of each point should be drawn
if (ovalDim < 1) // if it too small, make less small
ovalDim = 2;
g.fillOval((int)points[i].x, (int)points[i].y, (int)ovalDim, (int)ovalDim); //draw this oval
}
}
}
#Override
public void paintComponent(Graphics gg) {
super.paintComponent(gg);
Graphics2D g = (Graphics2D) gg;
g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
drawSphere(g);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setTitle("Sphere");
f.setResizable(false);
f.add(new SphereDrawing(), BorderLayout.CENTER);
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
});
}
#SuppressWarnings("rawtypes")
private class Coord implements Comparable {
public double x;
public double y;
public double z;
public Coord(double x2, double y2, double z2) {
x = x2;
y = y2;
z = z2;
}
public void scale() {
x *= SCALE;
y *= SCALE; //drawing purposes
z *= SCALE;
}
public String toString() {
return x + " " + y + " " + z;
}
public int compareTo(Object c) {
double diff = this.z - ((Coord)c).z;
if (diff < 0)
return -1;
else if (diff > 0) //for sorting the array of points
return 1;
else
return 0;
}
public boolean checkValid() {
return (z > 0); //checks if need to draw this point
}
}
}
I was hoping to at least draw a realistic looking sphere, even if not completely accurate, and I couldn't tell you what exactly is off with mine

How to 'Get' a Specific Point From A Shape Object Derived from AffineTransform

As a self-project, I'm trying to make the game 'Asteroids'.
Currently, I'm stuck on trying to figure out how to make it so the lasers fired from my ship appear from the tip of the ship. So far, I've tried experimenting with using the Shape object's .getBounds2D().getX() methods, but because getBounds2D() draws a rectangle around the polygon, the lasers end up appearing from the corner of the imaginary 'box' around my Polygon ship.
Here's a gif of what I have so far.
Is there a way to 'get' a specific point from a Shape object; where, in this case, that specific point is the tip of the ship.
Main Class:
public class AsteroidGame implements ActionListener, KeyListener{
public static AsteroidGame game;
public Renderer renderer;
public boolean keyDown = false;
public int playerAngle = 0;
public boolean left = false;
public boolean right = false;
public boolean go = false;
public boolean back = false;
public boolean still = true;
public double angle = 0;
public int turnRight = 5;
public int turnLeft = -5;
public Shape transformed;
public ArrayList<Laser> lasers;
public ArrayList<Shape> transformedLasers;
public final int WIDTH = 1400;
public final int HEIGHT = 800;
public Ship ship;
public Rectangle shipHead;
public Shape shipHeadTrans;
public Point headPoint;
public AffineTransform transform = new AffineTransform();
public AffineTransform lasTransform = new AffineTransform();
public AffineTransform headTransform = new AffineTransform();
public AsteroidGame(){
JFrame jframe = new JFrame();
Timer timer = new Timer(20, this);
renderer = new Renderer();
jframe.add(renderer);
jframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jframe.setSize(WIDTH, HEIGHT);
jframe.setVisible(true);
jframe.addKeyListener(this);
jframe.setResizable(false);
int xPoints[] = {800, 780, 800, 820};
int yPoints[] = {400, 460, 440, 460};
//(800, 400) is the initial location of the 'tip' of the ship'.
headPoint = new Point(800, 400);
lasers = new ArrayList<Laser>();
transformedLasers = new ArrayList<Shape>();
ship = new Ship(xPoints, yPoints, 4, 0);
transformed = transform.createTransformedShape(ship);
shipHead = new Rectangle(headPoint);
shipHeadTrans = transform.createTransformedShape(shipHead);
//shipHeadTrans.getBounds2D().
timer.start();
}
public void repaint(Graphics g){
g.setColor(Color.BLACK);
g.fillRect(0, 0, WIDTH, HEIGHT);
Graphics2D g2d = (Graphics2D)g;
//drawing the ship
g2d.setColor(Color.WHITE);
g2d.draw(transformed);
//drawing lasers
g2d.setColor(Color.RED);
for (int i = 0; i < transformedLasers.size(); i++){
System.out.println(i);
g2d.draw(transformedLasers.get(i));
}
}
public void actionPerformed(ActionEvent arg0) {
// TODO Auto-generated method stub
/*The for if and else if statements are just to send the ship
* to the other side of the canvas if it ever leaves the screen
*/
if (transformed.getBounds2D().getMinX() > WIDTH){
double tempAng = ship.getAng();
double diff = 90-tempAng;
transform.rotate(Math.toRadians(diff), ship.getCenterX(), ship.getCenterY());
transform.translate(0,WIDTH);
transform.rotate(Math.toRadians(-diff), ship.getCenterX(), ship.getCenterY());
}
else if (transformed.getBounds2D().getX() < 0){
double tempAng = ship.getAng();
double diff = 90-tempAng;
transform.rotate(Math.toRadians(diff), ship.getCenterX(), ship.getCenterY());
transform.translate(0,-WIDTH);
transform.rotate(Math.toRadians(-diff), ship.getCenterX(), ship.getCenterY());
}
else if (transformed.getBounds2D().getY() > HEIGHT){
double tempAng = ship.getAng();
double diff = 180-tempAng;
transform.rotate(Math.toRadians(diff), ship.getCenterX(), ship.getCenterY());
transform.translate(0,HEIGHT);
transform.rotate(Math.toRadians(-diff), ship.getCenterX(), ship.getCenterY());
}
else if (transformed.getBounds2D().getY() < 0){
double tempAng = ship.getAng();
double diff = 180-tempAng;
transform.rotate(Math.toRadians(diff), ship.getCenterX(), ship.getCenterY());
transform.translate(0,-HEIGHT);
transform.rotate(Math.toRadians(-diff), ship.getCenterX(), ship.getCenterY());
}
if (right){
ship.right();
//rotating the ship
transform.rotate(Math.toRadians(turnRight), ship.getCenterX(), ship.getCenterY());
//rotating the 'tip' of the ship.
headTransform.rotate(Math.toRadians(turnRight), ship.getCenterX(), ship.getCenterY());
}
else if (left){
ship.left();
//rotating the ship
transform.rotate(Math.toRadians(turnLeft), ship.getCenterX(), ship.getCenterY());
//rotating the 'tip' of the ship
headTransform.rotate(Math.toRadians(turnLeft), ship.getCenterX(), ship.getCenterY());
}
if (go){
ship.go();
}
else if (back){
ship.reverse();
}
//moving and shaping each individual laser that had been shot
for (int i = 0; i < transformedLasers.size(); i++){
lasers.get(i).move();
lasTransform = new AffineTransform();
lasTransform.rotate(Math.toRadians(lasers.get(i).getAng()), transformed.getBounds2D().getX(), transformed.getBounds2D().getY());
transformedLasers.set(i, lasTransform.createTransformedShape(lasers.get(i)));
}
//moving the ship
ship.move();
//moving the 'tip'
shipHead.y -= ship.getSpeed();
transformed = transform.createTransformedShape(ship);
shipHeadTrans = headTransform.createTransformedShape(shipHead);
renderer.repaint();
}
//defining a new laser
public void fireLaser(){
Laser tempLaser = new Laser((int)transformed.getBounds2D().getX(), (int)transformed.getBounds2D().getY(), 5, 10, ship.getAng());
lasers.add(tempLaser);
lasTransform = new AffineTransform();
lasTransform.rotate(Math.toRadians(ship.getAng()), transformed.getBounds2D().getX(), transformed.getBounds2D().getY());
transformedLasers.add(lasTransform.createTransformedShape(tempLaser));
}
public static void main(String[] args){
game = new AsteroidGame();
}
#Override
public void keyPressed(KeyEvent e) {
// TODO Auto-generated method stub
if (e.getKeyCode() == KeyEvent.VK_RIGHT){
right = true;
keyDown = true;
}else if (e.getKeyCode() == KeyEvent.VK_LEFT){
left = true;
keyDown = true;
}
else if (e.getKeyCode() == KeyEvent.VK_UP){
go = true;
}
else if (e.getKeyCode() == KeyEvent.VK_DOWN){
back = true;
}
//fire laser
if (e.getKeyCode() == KeyEvent.VK_SPACE){
fireLaser();
}
}
#Override
public void keyReleased(KeyEvent e) {
// TODO Auto-generated method stub
if (e.getKeyCode() == KeyEvent.VK_RIGHT){
right = false;
}
if (e.getKeyCode() == KeyEvent.VK_LEFT){
left = false;
}
if (e.getKeyCode() == KeyEvent.VK_UP){
go = false;
}
if (e.getKeyCode() == KeyEvent.VK_DOWN){
back = false;
}
still = true;
keyDown = false;
}
#Override
public void keyTyped(KeyEvent e) {
// TODO Auto-generated method stub
}
Ship Class (I don't think it's relevant though)
package asteroidGame;
import java.awt.Polygon;
import java.util.Arrays;
public class Ship extends Polygon{
/**
*
*/
private double currSpeed = 0;
private static final long serialVersionUID = 1L;
public double angle;
public int[] midX;
public int[] midY;
public Ship(int[] x, int[] y, int points, double angle){
super(x, y, points);
midX = x;
midY = y;
this.angle= angle;
}
public void right(){
angle += 5;
}
public void left(){
angle -= 5;
}
public void move(){
for (int i = 0; i < super.ypoints.length; i++){
super.ypoints[i] -= currSpeed;
//System.out.println(super.ypoints[i]);
//System.out.println(super.xpoints[i]);
}
//System.out.println(Arrays.toString(super.ypoints));
}
public double getSpeed(){
return currSpeed;
}
public void reverse(){
if (currSpeed > -15) currSpeed -= 0.2;
}
public void go(){
if (currSpeed < 25) currSpeed += 0.5;
}
public int getCenterX(){
return super.xpoints[2];
}
public int getCenterY(){
return super.ypoints[2];
}
public double getAng(){
return angle;
}
public void test(){
for (int x = 0; x < super.ypoints.length; x++){
super.ypoints[x] += 1000;
}
}
/*
public void decrement(){
if(currSpeed == 0){}
else if (currSpeed > 0 && currSpeed < 15){
currSpeed -= 0.05;
}
else if (currSpeed < 0 && currSpeed > -15){
currSpeed += 0.05;
}
System.out.println("losing speed");
}
*/
}
Laser Class (I don't think this is relevant either, but here ya go.)
package asteroidGame;
import java.awt.Color;
import java.awt.Rectangle;
import java.awt.geom.Rectangle2D;
public class Laser extends Rectangle{
private double angle;
public Laser(int x, int y , int width, int height, double ang){
super(x, y, width, height);
angle = ang;
Rectangle tst = new Rectangle();
}
public void move(){
super.y -= 35;
}
public double getAng(){
return angle;
}
public boolean intersects (Rectangle2D r){
//if intersects
if (super.intersects(r)){
return true;
}
else{
return false;
}
}
}
I was thinking of maybe turning the the Shape object transformed back into a Polygon to get the point, but I'm not sure how or if that would work.

You can use AffineTransform.transform(Point2D, Point2D) to transform a single point on your polygon.
Things would be a lot simpler for you if instead of trying to move the ship by using a rotation transform you kept a single (x,y) location of where the ship is. You'd move the ship's location in move() instead of trying to translate the polygon. Then when you want to paint the ship you e.g. do:
// Optionally copying the Graphics so the
// transform doesn't affect later painting.
Graphics2D temp = (Graphics2D) g2d.create();
temp.translate(ship.locX, ship.locY);
temp.rotate(ship.angle);
temp.draw(ship);
To move a point based on speed you can do this to find the movement vector:
double velX = speed * Math.cos(angle);
double velY = speed * Math.sin(angle);
locX += timeElapsed * velX;
locY += timeElapsed * velY;
That is essentially a conversion from polar to Cartesian coordinates. The x and y velocities are the legs of a triangle whose hypotenuse is speed and whose known angle is angle:
/|
/ |
/ |
/ |
speed / |
/ |
/ |velY
/ angle |
/)_______|
velX
There's an example of doing movement this way in an answer of mine here: https://stackoverflow.com/a/43692434/2891664.
For your comments:
Are you saying that, unlike my initial move function, just to make ship hold a single point, and thus I would only translate that instead?
More or less, yes. You'd still have a polygon to hold the ship's shape, but the points on the polygon would be relative to (0,0).
Suppose the following definitions:
Each (x,y) point on the polygon is pi. (In other words, one of p0, p1, p2 and p3.)
The (x,y) coordinates of the translation are T
Then, after translating the Graphics2D, each pi coordinate becomes pi+T on the panel. So if your polygon points are defined relative to (0,0) then translating to the ship's (locX,locY) will move the polygon to a location relative to (locX,locY).
It could be simplest then to define the point which is the tip of the polygon as being (0,0) so that after the translation the tip of the ship is the ship's location:
// Your original points:
int xPoints[] = {800, 780, 800, 820};
int yPoints[] = {400, 460, 440, 460};
// Become these points relative to (0,0):
int xPoints[] = {0, -20, 0, 20};
int yPoints[] = {0, 60, 40, 60};
And to e.g. start the ship in the same place, you would initialize its location to (800,400).
I was thinking about this again and realized the rotation is a little more complicated, because you probably don't want to rotate the ship around the tip. You probably want to rotate the ship around its center.
So, here's an MCVE demonstrating how to do all of this.
package mcve.game;
import javax.swing.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.awt.Polygon;
import java.awt.RenderingHints;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Rectangle;
import java.awt.Insets;
import java.awt.Toolkit;
import java.awt.GraphicsConfiguration;
import java.util.Set;
import java.util.HashSet;
import java.util.List;
import java.util.ArrayList;
public class MovementExample implements ActionListener {
public static void main(String[] args) {
SwingUtilities.invokeLater(MovementExample::new);
}
final int fps = 60;
final int period = 1000 / fps;
final JFrame frame;
final GamePanel panel;
final Controls controls;
final Ship ship;
final List<Bullet> bullets = new ArrayList<>();
MovementExample() {
frame = new JFrame("Movement Example");
Dimension size = getMaximumWindowSize(frame);
size.width /= 2;
size.height /= 2;
frame.setPreferredSize(size);
panel = new GamePanel();
frame.setContentPane(panel);
frame.pack();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
controls = new Controls();
ship = new Ship(panel.getWidth() / 2,
panel.getHeight() / 2);
new Timer(period, this).start();
}
#Override
public void actionPerformed(ActionEvent e) {
double secondsElapsed = 1.0 / fps;
ship.update(secondsElapsed);
bullets.forEach(b -> b.update(secondsElapsed));
Rectangle bounds = panel.getBounds();
bullets.removeIf(b -> !bounds.contains(b.locX, b.locY));
panel.repaint();
}
class GamePanel extends JPanel {
GamePanel() {
setBackground(Color.WHITE);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g.create();
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
if (ship != null) {
ship.draw(g2);
}
bullets.forEach(b -> b.draw(g2));
g2.dispose();
}
}
abstract class AbstractGameObject {
double maxSpeed;
double rotationAngle;
double locX;
double locY;
double velX;
double velY;
AbstractGameObject(double initialX, double initialY) {
locX = initialX;
locY = initialY;
}
abstract void update(double secondsElapsed);
abstract void draw(Graphics2D g2);
}
class Ship extends AbstractGameObject {
Polygon shape;
double rotationRate;
Ship(double initialX, double initialY) {
super(initialX, initialY);
maxSpeed = 128; // pixels/second
rotationAngle = Math.PI * 3 / 2;
rotationRate = (2 * Math.PI) / 2; // radians/second
int xPoints[] = {0, -20, 0, 20};
int yPoints[] = {0, 60, 40, 60};
shape = new Polygon(xPoints, yPoints, 4);
}
Point2D.Double getTip() {
Point2D.Double center = getCenter();
// The tip is at (0,0) and it's already centered
// on the x-axis origin, so the distance from the
// tip to the center is just center.y.
double distance = center.y;
// Then find the location of the tip, relative
// to the center.
double tipX = distance * Math.cos(rotationAngle);
double tipY = distance * Math.sin(rotationAngle);
// Now find the actual location of the center.
center.x += locX;
center.y += locY;
// And return the actual location of the tip, relative
// to the actual location of the center.
return new Point2D.Double(tipX + center.x, tipY + center.y);
}
Point2D.Double getCenter() {
// Returns the center point of the ship,
// relative to (0,0).
Point2D.Double center = new Point2D.Double();
for (int i = 0; i < shape.npoints; ++i) {
center.x += shape.xpoints[i];
center.y += shape.ypoints[i];
}
center.x /= shape.npoints;
center.y /= shape.npoints;
return center;
}
#Override
void update(double secondsElapsed) {
// See my answer here: https://stackoverflow.com/a/43692434/2891664
// for a discussion of why this logic is the way it is.
double speed = 0;
if (controls.isUpHeld()) {
speed += maxSpeed;
}
if (controls.isDownHeld()) {
speed -= maxSpeed;
}
velX = speed * Math.cos(rotationAngle);
velY = speed * Math.sin(rotationAngle);
locX += secondsElapsed * velX;
locY += secondsElapsed * velY;
double rotation = 0;
if (controls.isLeftHeld()) {
rotation -= rotationRate;
}
if (controls.isRightHeld()) {
rotation += rotationRate;
}
rotationAngle += secondsElapsed * rotation;
// Cap the angle so it can never e.g. get so
// large that it loses precision.
if (rotationAngle > 2 * Math.PI) {
rotationAngle -= 2 * Math.PI;
}
if (controls.isFireHeld()) {
Point2D.Double tipLoc = getTip();
Bullet bullet = new Bullet(tipLoc.x, tipLoc.y, rotationAngle);
bullets.add(bullet);
}
}
#Override
void draw(Graphics2D g2) {
Graphics2D copy = (Graphics2D) g2.create();
copy.setColor(Color.RED);
// Translate to the ship's location.
copy.translate(locX, locY);
// Rotate the ship around its center.
Point2D.Double center = getCenter();
// The PI/2 offset is necessary because the
// polygon points are defined with the ship
// already vertical, i.e. at an angle of -PI/2.
copy.rotate(rotationAngle + (Math.PI / 2), center.x, center.y);
copy.fill(shape);
}
}
class Bullet extends AbstractGameObject {
Ellipse2D.Double shape = new Ellipse2D.Double();
Bullet(double initialX, double initialY, double initialRotation) {
super(initialX, initialY);
maxSpeed = 512;
rotationAngle = initialRotation;
velX = maxSpeed * Math.cos(rotationAngle);
velY = maxSpeed * Math.sin(rotationAngle);
double radius = 3;
shape.setFrame(-radius, -radius, 2 * radius, 2 * radius);
}
#Override
void update(double secondsElapsed) {
locX += secondsElapsed * velX;
locY += secondsElapsed * velY;
}
#Override
void draw(Graphics2D g2) {
Graphics2D copy = (Graphics2D) g2.create();
copy.setColor(Color.BLACK);
copy.translate(locX, locY);
copy.fill(shape);
}
}
// See https://docs.oracle.com/javase/tutorial/uiswing/misc/keybinding.html
class Controls {
final Set<Integer> keysHeld = new HashSet<>();
Controls() {
bind(KeyEvent.VK_A, "left");
bind(KeyEvent.VK_D, "right");
bind(KeyEvent.VK_W, "up");
bind(KeyEvent.VK_S, "down");
bind(KeyEvent.VK_SPACE, "fire");
}
boolean isLeftHeld() { return keysHeld.contains(KeyEvent.VK_A); }
boolean isRightHeld() { return keysHeld.contains(KeyEvent.VK_D); }
boolean isUpHeld() { return keysHeld.contains(KeyEvent.VK_W); }
boolean isDownHeld() { return keysHeld.contains(KeyEvent.VK_S); }
boolean isFireHeld() { return keysHeld.contains(KeyEvent.VK_SPACE); }
void bind(int keyCode, String name) {
bind(keyCode, name, true);
bind(keyCode, name, false);
}
void bind(int keyCode, String name, boolean isOnRelease) {
KeyStroke stroke = KeyStroke.getKeyStroke(keyCode, 0, isOnRelease);
name += isOnRelease ? ".released" : ".pressed";
panel.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW)
.put(stroke, name);
panel.getActionMap()
.put(name, new AbstractAction() {
#Override
public void actionPerformed(ActionEvent e) {
if (isOnRelease) {
keysHeld.remove(keyCode);
} else {
keysHeld.add(keyCode);
}
}
});
}
}
// This returns the usable size of the display which
// the JFrame resides in, as described here:
// http://docs.oracle.com/javase/8/docs/api/java/awt/GraphicsEnvironment.html#getMaximumWindowBounds--
static Dimension getMaximumWindowSize(JFrame frame) {
GraphicsConfiguration config = frame.getGraphicsConfiguration();
Dimension size = config.getBounds().getSize();
Insets insets = Toolkit.getDefaultToolkit().getScreenInsets(config);
size.width -= insets.left + insets.right;
size.height -= insets.top + insets.bottom;
return size;
}
}
There are other ways the tip of the ship could be calculated, but the way I did it in the MCVE is this:
Get the center point of the ship, relative to (0,0).
Get the distance from the center point to the tip. The tip is at (0,0) so this is just the y-coordinate of the center.
Then calculate the (x,y) location of the tip, relative to the center. This is done in a very similar way to the figure above for speed and velocity, but the hypotenuse is the distance between the center and the tip of the ship.
Translate the center to be relative to the ship's location.
Translate the location of the tip (which is relative to the center) to be relative to the ship's location.
It could also all be done with an AffineTransform, similar to what you are doing in the code in the question, but you'd set it on every update. Something like this:
AffineTransform transform = new AffineTransform();
#Override
void update(double secondsElapsed) {
...
// Clear the previous translation and rotation.
transform.setToIdentity();
// Set to current.
transform.translate(locX, locY);
Point2D.Double center = getCenter();
transform.rotate(rotationAngle + (Math.PI / 2), center.x, center.y);
if (controls.isFireHeld()) {
Point2D.Double tip = new Point2D.Double(0, 0);
transform.transform(tip, tip);
Bullet bullet = new Bullet(tip.x, tip.y, rotationAngle);
bullets.add(bullet);
}
}
You could still use a transform to do calculations that way, but you don't end up with any strangeness from depending on the transform for movement. (In the code in the question, the ship is e.g. only ever moved along the y-axis. The apparent sideways movement is due to the series of rotation concatenations.)

Why is my direction so inaccurate for my normalized vector?

I'm designing a game and have gotten a lot of it working well. My one qualm is that my current method for moving a sprite from one point to another works well... but the direction is somewhat inaccurate. It wouldn't be so bad if the sprite didn't "snap" into place at the end of its path.
Is there any suggestion someone could make to either
a) Help improve the accuracy of my direction
b) Help make the sprite come into place more gently
Here is my code for calculating a movement from point A to B:
if (!mMoving) {
mMoving = true;
mVecStart = new Vec(mPos.getX(),mPos.getY());
mVecEnd = new Vec(target.getX(), target.getY());
mDistanceToDestination = Vec.distanceBetween(mVecEnd, mVecStart);
mDirection = mVecStart.directionTo(mVecEnd, mDistanceToDestination);
mVelocityX = mDirection.mDX * mSpeed;
mVelocityY = mDirection.mDY * mSpeed;
}
if (mMoving == true) {
// Move along the x and y axis at given velocity, scaled by deltaTime.
this.mPos.x += mVelocityX * deltaTime;
this.mPos.y += mVelocityY * deltaTime;
// If the distance traveled exceeds the original distance computed, snap the sprite
// into place immediately.
if (mMoving && Vec.distanceBetween(mVecStart, new Vec(this.mPos.x, this.mPos.y))
>= mDistanceToDestination) {
this.mPos.x = (int) target.getX();
this.mPos.y = (int) target.getY();
mMoving = false;
mMoveComplete = true;
}
}
Here is how direction is being calculated:
public Vec directionTo(Vec vecEnd, double distance) {
return new Vec((vecEnd.mDX - this.mDX) / distance,
((vecEnd.mDY - this.mDY) / distance));
}

You calculate the unit vector for a given vector by dividing each component by its magnitude.
Here's how I'd calculate the magnitude of a planar vector in a rectangular coordinate system:
package vector;
import java.awt.geom.Point2D;
/**
* Created by Michael
* Creation date 11/26/2016.
* #link
*/
public class VectorUtils {
public static double magnitude(Point2D beg, Point2D end) {
double magnitude = 0.0;
if ((beg != null) && (end != null)) {
double dx = Math.abs(end.getX()-beg.getX());
double dy = Math.abs(end.getY()-beg.getY());
if ((dx == 0.0) && (dy == 0.0)) {
magnitude = 0.0;
} else {
if (dx > dy) {
double r = dy/dx;
magnitude = dx*Math.sqrt(1.0+r*r);
} else {
double r = dx/dy;
magnitude = dy*Math.sqrt(1.0+r*r);
}
}
}
return magnitude;
}
}
You should learn how to use Junit to test your classes. You'll spend less time in a debugger or scratching your head over defects:
package vector;
import org.junit.Assert;
import org.junit.Test;
import java.awt.geom.Point2D;
/**
* Created by Michael
* Creation date 11/26/2016.
* #link
*/
public class VectorUtilsTest {
public static final double TOLERANCE = 1.0E-16;
#Test
public void testMagnitude_NullArguments() {
// setup
Point2D beg = null;
Point2D end = null;
// exercise and assert
Assert.assertEquals(0.0, VectorUtils.magnitude(beg, end), TOLERANCE);
}
#Test
public void testMagnitude_ZeroVector() {
// setup
Point2D beg = new Point2D.Double(0.0, 0.0);
Point2D end = new Point2D.Double(0.0, 0.0);
// exercise and assert
Assert.assertEquals(0.0, VectorUtils.magnitude(beg, end), TOLERANCE);
}
#Test
public void testMagnitude_UnitX() {
// setup
Point2D beg = new Point2D.Double(0.0, 0.0);
Point2D end = new Point2D.Double(2.0, 0.0);
// exercise and assert
Assert.assertEquals(2.0, VectorUtils.magnitude(beg, end), TOLERANCE);
}
#Test
public void testMagnitude_UnitY() {
// setup
Point2D beg = new Point2D.Double(0.0, 0.0);
Point2D end = new Point2D.Double(0.0, 2.0);
// exercise and assert
Assert.assertEquals(2.0, VectorUtils.magnitude(beg, end), TOLERANCE);
}
#Test
public void testMagnitude() {
// setup
Point2D beg = new Point2D.Double(0.0, 0.0);
Point2D end = new Point2D.Double(1.0, 1.0);
// exercise and assert
Assert.assertEquals(Math.sqrt(2.0), VectorUtils.magnitude(beg, end), TOLERANCE);
}
}

Java - Adjacency matrix based on distance between vertices

What I'm trying to do is come up with a way to generate n random points on a graph (displaying it isn't necessary). A point is randomly selected and connected to the point closest to it (or the next closest if it's already connected to the best option) in a way so that no two lines intersect. This repeats until no more connections are possible. The vertices are meant to represent regions on a map, and connections represent adjacency. The following code I have thus far is as follows, taken from http://javaingrab.blogspot.com/2012/12/m-way-graph-coloring-with-backtracking.html:
public class MWayGrColor{
/*G is graph's adjacency matrix and x is solution vector */
private int G[][],x[],n,m,soln;
public void mColoring(int k){ //backtracking function
for(int i=1;i<=n;i++){
next_color(k); //coloring kth vertex
if(x[k]==0)
return; //if unsuccessful then backtrack
if(k==n) //if all colored then show
write();
else
mColoring(k+1); /* successful but still left to color */
}
}
private void next_color(int k){
do{
int i=1;
x[k]=(x[k]+1)%(m+1);
if(x[k]==0)
return;
for(i=1;i<=n;i++)
if(G[i][k]!=0 && x[k]==x[i]) /* checking adjacency and not same color */
break;
if(i==n+1) return; //new color found
}while(true);
}
private void write(){
System.out.print("\nColoring(V C) # "+(++soln)+"-->");
for(int i=1;i<=n;i++)
System.out.print("\t("+i+" "+x[i]+")"); //solution vector
}
public void input(){
java.util.Scanner sc=new java.util.Scanner(System.in);
System.out.print("Enter no. of vertices : ");
n=sc.nextInt();
G=new int[n+1][n+1];
x=new int[n+1];
System.out.print("Enter no. of colors : ");
m=sc.nextInt();
System.out.println("Enter adjacency matrix-->");
for(int i=1;i<=n;i++)
for(int j=1;j<=n;j++)
G[i][j]=sc.nextInt();
}
public static void main (String[] args) {
MWayGrColor obj=new MWayGrColor();
obj.input();
obj.mColoring(1);
if(obj.soln==0)
System.out.println("\nNeed more than "+obj.m+" colors");
else
System.out.print("\nTOTAL SOLN : "+obj.soln);
}
}
As noted, the map doesn't need to be visually represented, as the current method of display is adequate. I'm aware of the Point2D.Double class and the Line2D class, and I was originally going to just start generating points and use the lines to create the adjacency matrix already shown in the code, but the methods for connecting points and avoiding repetition are extremely confusing to me in how they should be implemented. How can I accomplish this generation of an adjacency matrix?

It's still not clear what the actual question is. It sounds like "this is so complicated, I don't get it done". However, unless there are strict requirements about the approach and its running time etc., one can pragmatically write down what has to be done:
do
{
V v0 = randomVertex();
V v1 = findClosestUnconnected(v0);
if (line(v0,v1).intersectsNoOtherLine())
{
insert(line(v0,v1));
}
} while (insertedNewLine);
Of course, this implies some searching. For large graphs there may be some sophisticated data structures to accelerate this. Particularly the search for the nearest (unconnected) neighbor may be accelerated with the classical structures like KD-trees etc. But this seems to be unrelated to the original question.
The handing of the adjacency matrix can be made a bit more convenient with a wrapper that offers methods that allow a more "natural" description:
class Graph
{
private final boolean matrix[][];
void addEdge(V v0, V v1)
{
matrix[v0.index][v1.index] = true;
matrix[v1.index][v0.index] = true;
}
boolean hasEdge(V v0, V v1)
{
return matrix[v0.index][v1.index];
}
}
But in this case, this is only a minor, syntactical simplification.
An example, only as a VERY q&d sketch:
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Line2D;
import java.awt.geom.Point2D;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class NonIntersectingAdjacencies
{
public static void main(String[] args)
{
Random random = new Random(0);
int numVertices = 25;
List<AdjacencyVertex> vertices =
createRandomVertices(numVertices, random);
final AdjacencyGraph adjacencyGraph =
new AdjacencyGraph(vertices);
boolean createdNewLine = true;
while (createdNewLine)
{
createdNewLine = false;
List<Integer> indices =
createShuffledList(numVertices, random);
for (int i=0; i<numVertices; i++)
{
int randomIndex = indices.get(i);
AdjacencyVertex randomVertex = vertices.get(randomIndex);
AdjacencyVertex closest =
findClosestUnconnected(randomVertex, adjacencyGraph);
if (closest != null)
{
if (!intersectsOtherLine(
randomVertex, closest, adjacencyGraph))
{
adjacencyGraph.addEdge(randomVertex, closest);
createdNewLine = true;
}
}
}
}
AdjacencyGraphPanel.show(adjacencyGraph);
}
private static List<AdjacencyVertex> createRandomVertices(
int numVertices, Random random)
{
List<AdjacencyVertex> vertices = new ArrayList<AdjacencyVertex>();
for (int i=0; i<numVertices; i++)
{
AdjacencyVertex v = new AdjacencyVertex();
v.index = i;
v.x = random.nextDouble();
v.y = random.nextDouble();
vertices.add(v);
}
return vertices;
}
private static List<Integer> createShuffledList(
int maxValue, Random random)
{
List<Integer> list = new ArrayList<Integer>();
for (int i=0; i<maxValue; i++)
{
list.add(i);
}
Collections.shuffle(list, random);
return list;
}
private static boolean intersectsOtherLine(
AdjacencyVertex v0, AdjacencyVertex v1,
AdjacencyGraph adjacencyGraph)
{
Line2D newLine = new Line2D.Double(
v0.x, v0.y, v1.x, v1.y);
List<AdjacencyVertex> vertices = adjacencyGraph.getVertices();
for (int i=0; i<vertices.size(); i++)
{
for (int j=0; j<vertices.size(); j++)
{
if (i == j)
{
continue;
}
AdjacencyVertex oldV0 = vertices.get(i);
AdjacencyVertex oldV1 = vertices.get(j);
if (adjacencyGraph.hasEdge(oldV0, oldV1))
{
Line2D oldLine = new Line2D.Double(
oldV0.x, oldV0.y, oldV1.x, oldV1.y);
if (Intersection.intersect(oldLine, newLine))
{
return true;
}
}
}
}
return false;
}
private static AdjacencyVertex findClosestUnconnected(
AdjacencyVertex v,
AdjacencyGraph adjacencyGraph)
{
double minDistanceSquared = Double.MAX_VALUE;
AdjacencyVertex closest = null;
List<AdjacencyVertex> vertices = adjacencyGraph.getVertices();
for (int i=0; i<vertices.size(); i++)
{
AdjacencyVertex other = vertices.get(i);
if (other.index == v.index)
{
continue;
}
if (adjacencyGraph.hasEdge(v, other))
{
continue;
}
double dx = other.x - v.x;
double dy = other.y - v.y;
double distanceSquared = Math.hypot(dx, dy);
if (distanceSquared < minDistanceSquared)
{
minDistanceSquared = distanceSquared;
closest = other;
}
}
return closest;
}
}
class AdjacencyVertex
{
double x;
double y;
int index;
}
class AdjacencyGraph
{
private final boolean matrix[][];
private final List<AdjacencyVertex> vertices;
AdjacencyGraph(List<AdjacencyVertex> vertices)
{
this.vertices = vertices;
this.matrix = new boolean[vertices.size()][vertices.size()];
}
List<AdjacencyVertex> getVertices()
{
return vertices;
}
void addEdge(AdjacencyVertex v0, AdjacencyVertex v1)
{
matrix[v0.index][v1.index] = true;
matrix[v1.index][v0.index] = true;
}
boolean hasEdge(AdjacencyVertex v0, AdjacencyVertex v1)
{
return matrix[v0.index][v1.index];
}
}
//============================================================================
// Only helper stuff below this line...
class AdjacencyGraphPanel extends JPanel
{
public static void show(final AdjacencyGraph adjacencyGraph)
{
SwingUtilities.invokeLater(new Runnable()
{
#Override
public void run()
{
createAndShowGUI(adjacencyGraph);
}
});
}
private static void createAndShowGUI(AdjacencyGraph adjacencyGraph)
{
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.getContentPane().add(new AdjacencyGraphPanel(adjacencyGraph));
f.setSize(600,600);
f.setLocationRelativeTo(null);
f.setVisible(true);
}
private final AdjacencyGraph adjacencyGraph;
public AdjacencyGraphPanel(AdjacencyGraph adjacencyGraph)
{
this.adjacencyGraph = adjacencyGraph;
}
#Override
protected void paintComponent(Graphics gr)
{
super.paintComponent(gr);
Graphics2D g = (Graphics2D)gr;
int offsetX = 30;
int offsetY = 30;
int w = getWidth() - offsetX - offsetX;
int h = getHeight() - offsetY - offsetY;
g.setColor(Color.BLACK);
List<AdjacencyVertex> vertices = adjacencyGraph.getVertices();
for (int i=0; i<vertices.size(); i++)
{
for (int j=0; j<vertices.size(); j++)
{
if (i == j)
{
continue;
}
AdjacencyVertex v0 = vertices.get(i);
AdjacencyVertex v1 = vertices.get(j);
if (adjacencyGraph.hasEdge(v0, v1))
{
Line2D newLine = new Line2D.Double(
offsetX + v0.x*w,
offsetY + v0.y*h,
offsetX + v1.x*w,
offsetY + v1.y*h);
g.draw(newLine);
}
}
}
g.setColor(Color.BLUE);
for (int i=0; i<vertices.size(); i++)
{
AdjacencyVertex v = vertices.get(i);
int ix = (int)(offsetX + v.x * w);
int iy = (int)(offsetY + v.y * h);
g.fill(new Ellipse2D.Double(
ix - 5, iy - 5, 10, 10));
g.drawString(String.valueOf(i), ix, iy+16);
}
}
}
class Intersection
{
static boolean intersect(Line2D line0, Line2D line1)
{
Point2D location = new Point2D.Double();
Point2D intersection =
Intersection.computeIntersectionSegmentSegment(
line0, line1, location);
if (intersection == null)
{
return false;
}
return !isAtLineAnd(location);
}
private static boolean isAtLineAnd(Point2D location)
{
double EPSILON = 0.05;
if (Math.abs(location.getX()) < EPSILON)
{
return true;
}
if (Math.abs(location.getX()-1) < EPSILON)
{
return true;
}
if (Math.abs(location.getY()) < EPSILON)
{
return true;
}
if (Math.abs(location.getY()-1) < EPSILON)
{
return true;
}
return false;
}
/**
* Epsilon for floating point computations
*/
private static final double epsilon = 1e-6f;
/**
* Computes the intersection of the specified line segments and returns
* the intersection point, or <code>null</code> if the line segments do
* not intersect.
*
* #param line0 The first line segment
* #param line1 The second line segment
* #param location Optional location that stores the
* relative location of the intersection point on
* the given line segments
* #return The intersection point, or <code>null</code> if
* there is no intersection.
*/
public static Point2D computeIntersectionSegmentSegment(
Line2D line0, Line2D line1, Point2D location)
{
return computeIntersectionSegmentSegment(
line0.getX1(), line0.getY1(), line0.getX2(), line0.getY2(),
line1.getX1(), line1.getY1(), line1.getX2(), line1.getY2(),
location);
}
/**
* Computes the intersection of the specified line segments and returns
* the intersection point, or <code>null</code> if the line segments do
* not intersect.
*
* #param s0x0 x-coordinate of point 0 of line segment 0
* #param s0y0 y-coordinate of point 0 of line segment 0
* #param s0x1 x-coordinate of point 1 of line segment 0
* #param s0y1 y-coordinate of point 1 of line segment 0
* #param s1x0 x-coordinate of point 0 of line segment 1
* #param s1y0 y-coordinate of point 0 of line segment 1
* #param s1x1 x-coordinate of point 1 of line segment 1
* #param s1y1 y-coordinate of point 1 of line segment 1
* #param location Optional location that stores the
* relative location of the intersection point on
* the given line segments
* #return The intersection point, or <code>null</code> if
* there is no intersection.
*/
public static Point2D computeIntersectionSegmentSegment(
double s0x0, double s0y0,
double s0x1, double s0y1,
double s1x0, double s1y0,
double s1x1, double s1y1,
Point2D location)
{
if (location == null)
{
location = new Point2D.Double();
}
Point2D result = computeIntersectionLineLine(
s0x0, s0y0, s0x1, s0y1, s1x0, s1y0, s1x1, s1y1, location);
if (location.getX() >= 0 && location.getX() <= 1.0 &&
location.getY() >= 0 && location.getY() <= 1.0)
{
return result;
}
return null;
}
/**
* Computes the intersection of the specified lines and returns the
* intersection point, or <code>null</code> if the lines do not
* intersect.
*
* Ported from
* http://www.geometrictools.com/LibMathematics/Intersection/
* Wm5IntrSegment2Segment2.cpp
*
* #param s0x0 x-coordinate of point 0 of line segment 0
* #param s0y0 y-coordinate of point 0 of line segment 0
* #param s0x1 x-coordinate of point 1 of line segment 0
* #param s0y1 y-coordinate of point 1 of line segment 0
* #param s1x0 x-coordinate of point 0 of line segment 1
* #param s1y0 y-coordinate of point 0 of line segment 1
* #param s1x1 x-coordinate of point 1 of line segment 1
* #param s1y1 y-coordinate of point 1 of line segment 1
* #param location Optional location that stores the
* relative location of the intersection point on
* the given line segments
* #return The intersection point, or <code>null</code> if
* there is no intersection.
*/
public static Point2D computeIntersectionLineLine(
double s0x0, double s0y0,
double s0x1, double s0y1,
double s1x0, double s1y0,
double s1x1, double s1y1,
Point2D location)
{
double dx0 = s0x1 - s0x0;
double dy0 = s0y1 - s0y0;
double dx1 = s1x1 - s1x0;
double dy1 = s1y1 - s1y0;
double len0 = Math.sqrt(dx0*dx0+dy0*dy0);
double len1 = Math.sqrt(dx1*dx1+dy1*dy1);
double dir0x = dx0 / len0;
double dir0y = dy0 / len0;
double dir1x = dx1 / len1;
double dir1y = dy1 / len1;
double c0x = s0x0 + dx0 * 0.5;
double c0y = s0y0 + dy0 * 0.5;
double c1x = s1x0 + dx1 * 0.5;
double c1y = s1y0 + dy1 * 0.5;
double cdx = c1x - c0x;
double cdy = c1y - c0y;
double dot = dotPerp(dir0x, dir0y, dir1x, dir1y);
if (Math.abs(dot) > epsilon)
{
double dot0 = dotPerp(cdx, cdy, dir0x, dir0y);
double dot1 = dotPerp(cdx, cdy, dir1x, dir1y);
double invDot = 1.0/dot;
double s0 = dot1*invDot;
double s1 = dot0*invDot;
if (location != null)
{
double n0 = (s0 / len0) + 0.5;
double n1 = (s1 / len1) + 0.5;
location.setLocation(n0, n1);
}
double x = c0x + s0 * dir0x;
double y = c0y + s0 * dir0y;
return new Point2D.Double(x,y);
}
return null;
}
/**
* Returns the perpendicular dot product, i.e. the length
* of the vector (x0,y0,0)x(x1,y1,0).
*
* #param x0 Coordinate x0
* #param y0 Coordinate y0
* #param x1 Coordinate x1
* #param y1 Coordinate y1
* #return The length of the cross product vector
*/
private static double dotPerp(double x0, double y0, double x1, double y1)
{
return x0*y1 - y0*x1;
}
}

Java OpenCV deskewing a contour

I have made some progress detecting a specific kind of object. Actually a card, just like any other in your wallet.
Now I'm stuck with deskewing the photo. See:
The blue (rounded) rectangle represents the detected contour.
The purple rotate rectangle represents a RotatedRect extracted from the detected contour.
The green line is just the bounding box.
Well I need neither of those rectangles. The rectangles both have 90 degree corners. Which won't get me the perspective.
My question:
How can I get as accurate as possible all quadrangle corners from a contour?

I have created a class Quadrangle which creates the quadrangle of the 4 most largest connected polygon vertices which will intersect each other at some point. This will work in nearly any case.
If you use this code, remember to adjust the width and height in Quadrangle.warp. Note that it isn't 100% complete, the first and last polygon vertices won't be connected if they may be connect for example.
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import org.opencv.core.*;
import org.opencv.imgproc.Imgproc;
class Line {
public Point offset;
public double angle;
public Line(Point offset, double angle) {
this.offset = offset.clone();
this.angle = angle;
}
public Point get(int length) {
Point result = offset.clone();
result.x += Math.cos(angle) * length;
result.y += Math.sin(angle) * length;
return result;
}
public Point getStart() {
return get(-5000);
}
public Point getEnd() {
return get(5000);
}
public void scale(double factor) {
offset.x *= factor;
offset.y *= factor;
}
public static Point intersect(Line l1, Line l2) {
return getLineLineIntersection(l1.getStart().x, l1.getStart().y, l1.getEnd().x, l1.getEnd().y,
l2.getStart().x, l2.getStart().y, l2.getEnd().x, l2.getEnd().y
);
}
public static Point getLineLineIntersection(double x1, double y1, double x2, double y2, double x3, double y3, double x4, double y4) {
double det1And2 = det(x1, y1, x2, y2);
double det3And4 = det(x3, y3, x4, y4);
double x1LessX2 = x1 - x2;
double y1LessY2 = y1 - y2;
double x3LessX4 = x3 - x4;
double y3LessY4 = y3 - y4;
double det1Less2And3Less4 = det(x1LessX2, y1LessY2, x3LessX4, y3LessY4);
if (det1Less2And3Less4 == 0){
// the denominator is zero so the lines are parallel and there's either no solution (or multiple solutions if the lines overlap) so return null.
return null;
}
double x = (det(det1And2, x1LessX2,
det3And4, x3LessX4) /
det1Less2And3Less4);
double y = (det(det1And2, y1LessY2,
det3And4, y3LessY4) /
det1Less2And3Less4);
return new Point(x, y);
}
protected static double det(double a, double b, double c, double d) {
return a * d - b * c;
}
}
class LineSegment extends Line implements Comparable {
public double length;
public LineSegment(Point offset, double angle, double length) {
super(offset, angle);
this.length = length;
}
public void melt(LineSegment segment) {
Point point = new Point();
point.x += Math.cos(angle) * length;
point.y += Math.sin(angle) * length;
point.x += Math.cos(segment.angle) * segment.length;
point.y += Math.sin(segment.angle) * segment.length;
angle = Math.atan2(point.y, point.x);
offset.x = (offset.x * length + segment.offset.x * segment.length) / (length + segment.length);
offset.y = (offset.y * length + segment.offset.y * segment.length) / (length + segment.length);
length += segment.length;
}
#Override
public int compareTo(Object other) throws ClassCastException {
if (!(other instanceof LineSegment)) {
throw new ClassCastException("A LineSegment object expected.");
}
return (int) (((LineSegment) other).length - this.length);
}
}
class Quadrangle {
static int
TOP = 0,
RIGHT = 1,
BOTTOM = 2,
LEFT = 3;
public Line[] lines = new Line[4];
public Quadrangle() {
}
private static double getAngle(Point p1, Point p2) {
return Math.atan2(p2.y - p1.y, p2.x - p1.x);
}
private static double getLength(Point p1, Point p2) {
return Math.sqrt(Math.pow(p2.x - p1.x, 2) + Math.pow(p2.y - p1.y, 2));
}
private static double roundAngle(double angle) {
return angle - (2*Math.PI) * Math.round(angle / (2 * Math.PI));
}
public static Quadrangle fromContour(MatOfPoint contour) {
List<Point> points = contour.toList();
List<LineSegment> segments = new ArrayList<>();
// Create line segments
for (int i = 0; i < points.size(); i++) {
double a = getAngle(points.get(i), points.get((i + 1) % points.size()));
double l = getLength(points.get(i), points.get((i + 1) % points.size()));
segments.add(new LineSegment(points.get(i), a, l));
}
// Connect line segments
double angleDiffMax = 2 * Math.PI / 100;
List<LineSegment> output = new ArrayList<>();
for (LineSegment segment : segments) {
if (output.isEmpty()) {
output.add(segment);
} else {
LineSegment top = output.get(output.size() - 1);
double d = roundAngle(segment.angle - top.angle);
if (Math.abs(d) < angleDiffMax) {
top.melt(segment);
} else {
output.add(segment);
}
}
}
Collections.sort(output);
Quadrangle quad = new Quadrangle();
for (int o = 0; o < 4; o += 1) {
for (int i = 0; i < 4; i++) {
if (Math.abs(roundAngle(output.get(i).angle - (2 * Math.PI * o / 4))) < Math.PI / 4) {
quad.lines[o] = output.get(i);
}
}
}
return quad;
}
public void scale(double factor) {
for (int i = 0; i < 4; i++) {
lines[i].scale(factor);
}
}
public Mat warp(Mat src) {
Mat result = src.clone();
Core.line(result, lines[TOP].get(-5000), lines[TOP].get(5000), new Scalar(200, 100, 100), 8);
Core.line(result, lines[RIGHT].get(-5000), lines[RIGHT].get(5000), new Scalar(0, 255, 0), 8);
Core.line(result, lines[BOTTOM].get(-5000), lines[BOTTOM].get(5000), new Scalar(255, 0, 0), 8);
Core.line(result, lines[LEFT].get(-5000), lines[LEFT].get(5000), new Scalar(0, 0, 255), 8);
Point p = Line.intersect(lines[TOP], lines[LEFT]);
System.out.println(p);
if (p != null) {
Core.circle(result, p, 30, new Scalar(0, 0, 255), 8);
}
double width = 1400;
double height = width / 2.15;
Point[] srcProjection = new Point[4], dstProjection = new Point[4];
srcProjection[0] = Line.intersect(lines[TOP], lines[LEFT]);
srcProjection[1] = Line.intersect(lines[TOP], lines[RIGHT]);
srcProjection[2] = Line.intersect(lines[BOTTOM], lines[LEFT]);
srcProjection[3] = Line.intersect(lines[BOTTOM], lines[RIGHT]);
dstProjection[0] = new Point(0, 0);
dstProjection[1] = new Point(width - 1, 0);
dstProjection[2] = new Point(0, height - 1);
dstProjection[3] = new Point(width - 1, height - 1);
Mat warp = Imgproc.getPerspectiveTransform(new MatOfPoint2f(srcProjection), new MatOfPoint2f(dstProjection));
Mat rotated = new Mat();
Size size = new Size(width, height);
Imgproc.warpPerspective(src, rotated, warp, size, Imgproc.INTER_LINEAR);
return rotated;
}
}