Develop Reference

Perceptron doesn't find the right line even with a bias (Processing)

My perceptron doesn't find the right y-intercept even though I added a bias. The slope is correct. This is my second try coding a perceptron from scratch and I got the same error twice.
The perceptron evaluates if a point on a canvas is higher or lower than the interception line. The inputs are the x-coordinate, y-coordinate and 1 for the bias.
Perceptron class:
class Perceptron
{
float[] weights;
Perceptron(int layerSize)
{
weights = new float[layerSize];
for (int i = 0; i < layerSize; i++)
{
weights[i] = random(-1.0,1.0);
}
}
float Evaluate(float[] input)
{
float sum = 0;
for (int i = 0; i < weights.length; i++)
{
sum += weights[i] * input[i];
}
return sum;
}
float Learn(float[] input, int expected)
{
float guess = Evaluate(input);
float error = expected - guess;
for (int i = 0; i < weights.length; i++)
{
weights[i] += error * input[i] * 0.01;
}
return guess;
}
}
This is the testing code:
PVector[] points;
float m = 1; // y = mx+q (in canvas space)
float q = 0; //
Perceptron brain;
void setup()
{
size(600,600);
points = new PVector[100];
for (int i = 0; i < points.length; i++)
{
points[i] = new PVector(random(0,width),random(0,height));
}
brain = new Perceptron(3);
}
void draw()
{
background(255);
DrawGraph();
DrawPoints();
//noLoop();
}
void DrawPoints()
{
for (int i = 0; i < points.length; i++)
{
float[] input = new float[] {points[i].x / width, points[i].y / height, 1};
int expected = ((m * points[i].x + q) < points[i].y) ? 1 : 0; // is point above line
float output = brain.Learn(input, expected);
fill(sign(output) * 255);
stroke(expected*255,100,100);
strokeWeight(3);
ellipse(points[i].x, points[i].y, 20, 20);
}
}
int sign(float x)
{
return x >= 0 ? 1 : 0;
}
void DrawGraph()
{
float y1 = 0 * m + q;
float y2 = width * m + q;
stroke(255,100,100);
strokeWeight(3);
line(0,y1,width,y2);
}

I found the problem
float guess = Evaluate(input);
float error = expected - guess;
should be
float guess = sign(Evaluate(input));
float error = expected - guess;
The output was never exactly one ore zero even if the answer would be correct. Because of this even the correct points gave a small error that stopped the perceptron from finding the right answer. By calculating the sign of the answer first the error is 0 if the answer is correct.

Android canvas. How to set circles at random position?

Below code generated and save position x y to HashMap and check collision two circles;
HashMap<Integer, Float> posX = new HashMap<>();
HashMap<Integer, Float> posY = new HashMap<>();
int numberOfCircle = 8;
for(int i=0; i < numberOfCircle; i ++){
// boolean flag = false;
while (true){
float x =random.nextInt(width - raduis/2) + raduis/2f;
float y =random.nextInt(height - raduis/2) + raduis/2f;
if(!posX.containsValue(x) && !posY.containsValue(y)){
if(i == 0){
posX.put(i, x);
posY.put(i, y);
break;
}
if(i > 0){
double distance = Math.sqrt(((posX.get(i - 1) - x) * (posX.get(i - 1) - x)) + ((posY.get(i - 1) - y) * ( posY.get(i - 1) - y)));
if (distance > raduis+raduis) {
posX.put(i, x);
posY.put(i, y);
Log.d(TAG, i + " xPos=" + posX.get(i) + " yPos=" + posY.get(i) + " distance=" + distance);
break;
}
if(numberOfCircle == posX.size()) break;
}
}
}
}
This code work only if circle count=2; But when circle count > 2 i have collision; How to check current generated position for each in HashMap?
For example:
xPos = {5, 10, 3}
yPos = {10, 33, 5}
generated position x=6, y=10;
calculate distance between x=6, y=10 with all positions in Map. If distance < radius+radius generate new position while distance > radius+radius;
Update ========================>
My code work like
I want like this
output: distance equal between current generated position(X, Y) and previous position(X, Y). I want to check between current generated x, y with all added positons in HashMap.
D/DEBUG DATA ===>: 1 xPos=432.0 yPos=411.0 distance=390.6430595825299
D/DEBUG DATA ===>: 2 xPos=316.0 yPos=666.0 distance=280.1446055165082
D/DEBUG DATA ===>: 3 xPos=244.0 yPos=83.0 distance=587.4291446634223
D/DEBUG DATA ===>: 4 xPos=214.0 yPos=551.0 distance=468.96055271205915
D/DEBUG DATA ===>: 5 xPos=76.0 yPos=1011.0 distance=480.2540994098853
D/DEBUG DATA ===>: 6 xPos=289.0 yPos=868.0 distance=256.55019002136794
D/DEBUG DATA ===>: 7 xPos=494.0 yPos=988.0 distance=237.53947040439405
P.s Sorry so poor English.

Maybe something closer to this will work? I'm not entirely sure if it's what you want or if it will help, but I did a quick rewrite for clarity.
HashMap<Integer, Integer> posX = new HashMap<>();
HashMap<Integer, Integer> posY = new HashMap<>();
final int circlesToPlace = 8;
for(int i = 0 ; i < circlesToPlace ; i++){
// boolean flag = false;
while (true){
final int x = ThreadLocalRandom.current().nextInt((radius/2f), width + 1);
final int y = ThreadLocalRandom.current().nextInt((radius/2f), height + 1);
// Iterate over all other positions to ensure no circle intersects with
// the new circle.
for (int index = 0 ; index < posX.size() ; index++) {
// Calculate distance where d = sqrt((x2 - x1)^2 + (y2 - y1)^2)
final int otherX = posX.get(index);
final int otherY = posY.get(index);
int differenceX = otherX - x;
differenceX *= differenceX;
int differenceY = otherY - y;
differenceY *= differenceY;
final double distance = Math.sqrt(differenceX + differenceY);
if (distance > (radius * 2)) {
posX.put(i, x);
posY.put(i, y);
Log.d(TAG, i + " xPos=" + posX.get(i) + " yPos=" + posY.get(i) + " distance=" + distance);
break;
}
}
}
}

My variant. You don't need to do sqrt to compare distance, you can instead square the constant (d2 in my case).
Random random = new Random();
int numberOfCircle = 8, width = 400, height = 300;
int diameter = 51;
final float radius = diameter * 0.5f;
final float d2 = diameter * diameter;
List<Float> posX = new ArrayList<>(numberOfCircle);
List<Float> posY = new ArrayList<>(numberOfCircle);
while (posX.size() < numberOfCircle) { // till enough generated
// generate new coordinates
float x = random.nextInt(width - diameter) + radius;
float y = random.nextInt(height - diameter) + radius;
System.out.printf("Generated [%3.3f, %3.3f] ... ", x, y);
// verify it does not overlap/touch with previous circles
int j = 0;
while (j < posX.size()) {
float dx = posX.get(j) - x, dy = posY.get(j) - y;
float diffSquare = (dx * dx) + (dy * dy);
if (diffSquare <= d2) break;
++j;
}
// generate another pair of coordinates, if it does touch previous
if (j != posX.size()) {
System.out.println("collided.");
continue;
}
System.out.println("added.");
// not overlapping/touch, add as new circle
posX.add(x);
posY.add(y);
} // while (posX.size() < numberOfCircle)

I resolve like this
private class MyView extends View implements View.OnTouchListener{
List<Circle> randomCircles = new ArrayList<>();
int radius = new Circle().getRadius();
int randomCircleCount = 3;
Random random = new Random();
public MyView(Context context) {
super(context);
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
//Integer width = canvas.getWidth();
Integer width = canvas.getWidth();
Integer height = canvas.getHeight() - (radius);
// Integer height = canvas.getHeight()/2 + canvas.getHeight();
///randomCircles.clear();
Paint paint = new Paint();
paint.setStyle(Paint.Style.FILL);
paint.setColor(Color.BLACK);
canvas.drawPaint(paint);
Paint paintT = new Paint();
paintT.setTextSize(18f);
paintT.setAntiAlias(true);
paintT.setTextAlign(Paint.Align.CENTER);
while(randomCircles.size() < randomCircleCount){
randomCircle(width, height);
}
for(int i=0; i < randomCircleCount; i ++){
Circle circle = randomCircles.get(i);
float curPosX = randomCircles.get(i).getCx().floatValue();
float curPosY = randomCircles.get(i).getCy().floatValue();
int r = random.nextInt(256);
int g = random.nextInt(256);
int b = random.nextInt(256);
paint.setARGB(175, 77, 2, 200);
//if(r != 0 && g != 0 && b != 0) paint.setARGB(255, r, g, b);
canvas.drawCircle(curPosX, curPosY, radius, paint);
Rect bounds = new Rect();
String text = "" +i;
paintT.getTextBounds(text, 0, text.length(), bounds);
paint.setAntiAlias(true);
canvas.drawText(text, curPosX, curPosY, paintT);
circle.update(width, height);
//Log.d(TAG, "REDRAW");
}
///invalidate();
postInvalidateDelayed(100);
}
private void randomCircle(int width, int height) {
double x = getPosX(width, radius);
double y = getPosY(height,radius);
boolean hit = false;
for (int i = 0; i < randomCircles.size(); i++) {
Circle circle = randomCircles.get(i);
double dx = circle.getCx() - x;
double dy = circle.getCy() - y;
int r = circle.getRadius() + radius;
if (dx * dx + dy * dy <= r * r) {
Log.d(TAG, "dx=" + dx + " dy=" + dy);
hit = true;
}
}
if (!hit) {
Log.d(TAG, "Here!!!!!");
randomCircles.add(new Circle(x, y));
}
}
private Float getPosX(Integer width, Integer radius){
return random.nextInt(width - radius/2) + radius/2f;
}
private Float getPosY(Integer height, Integer radius){
return random.nextInt(height - radius/2) + radius/2f;
}

java graphics gouraud shading

I want to fill triangles with gouraud shading
I calculated normals for each vertex and used the following code but it dosn't work correctly
I interpolated colors against y using these formulas
Ir = Ir2 - (Ir2 - Ir1)* (v2.y -y)/dy;
Ig = Ig2 - (Ig2 - Ig1)* (v2.y -y)/dy;
Ib = Ib2 - (Ib2 - Ib1)* (v2.y -y)/dy;
and against x direction using
rr = r2- (r2-r1)*(Xs2-j)/dxs;
in method drawCurrentTriangle(Graphics2D g) how can i calculate color from interpolated vertex normal.(there is no lights in the scene (only triangle color))
public boolean convert(Triangle triangle) {
ensureCapacity();
clearCurrentScan();
triangle.getVlist()[0].r = triangle.normals[0].x;
triangle.getVlist()[0].g = triangle.normals[0].y;
triangle.getVlist()[0].b = triangle.normals[0].z;
triangle.getVlist()[1].r = triangle.normals[1].x;
triangle.getVlist()[1].g = triangle.normals[1].y;
triangle.getVlist()[1].b = triangle.normals[1].z;
triangle.getVlist()[2].r = triangle.normals[2].x;
triangle.getVlist()[2].g = triangle.normals[2].y;
triangle.getVlist()[2].b = triangle.normals[2].z;
for (int i = 0; i < 3; i++) {
Vector3d v1 = triangle.getVlist()[i];
Vector3d v2;
if (i == 2) {
v2 = triangle.getVlist()[0];
} else {
v2 = triangle.getVlist()[i + 1];
}
// ensure v1.y < v2.y
if (v1.y > v2.y) {
Vector3d temp = v1;
v1 = v2;
v2 = temp;
}
double dy = v2.y - v1.y;
Ir1 = v1.r;
Ig1 = v1.g;
Ib1 = v1.b;
Ir2 = v2.r;
Ig2 = v2.g;
Ib2 = v2.b;
// ignore horizontal lines
if (dy == 0) {
continue;
}
int startY = Math.max(FastMath.ceil(v1.y), minY);
int endY = Math.min(FastMath.ceil(v2.y) - 1, maxY);
top = Math.min(top, startY);
bottom = Math.max(bottom, endY);
double dx = v2.x - v1.x;
double Ir;
double Ig;
double Ib;
double Ic;
double Ia;
double Yc;
// special case: vertical line
if (dx == 0) {
int x = FastMath.ceil(v1.x);
// ensure x within view bounds
x = Math.min(maxX + 1, Math.max(x, minX));
for (int y = startY; y <= endY; y++) {
Ir = Ir2 - (Ir2 - Ir1)* (v2.y -y)/dy;
Ig = Ig2 - (Ig2 - Ig1)* (v2.y -y)/dy;
Ib = Ib2 - (Ib2 - Ib1)* (v2.y -y)/dy;
scans[y].setBoundary(x, Ir, Ig, Ib);
}
} else {
// scan-convert this edge (line equation)
double gradient = dx / dy;
// (slower version)
for (int y = startY; y <= endY; y++) {
int x = FastMath.ceil(v1.x + (y - v1.y) * gradient);
// ensure x within view bounds
x = Math.min(maxX + 1, Math.max(x, minX));
Ir = Ir2 - (Ir2 - Ir1)* (v2.y -y)/dy;
Ig = Ig2 - (Ig2 - Ig1)* (v2.y -y)/dy;
Ib = Ib2 - (Ib2 - Ib1)* (v2.y -y)/dy;
scans[y].setBoundary(x, Ir, Ig, Ib);
}
// check if visible (any valid scans)
for (int i = top; i <= bottom; i++) {
if (scans[i].isValid()) {
return true;
}
}
return false;
}
}
}
protected void drawCurrentTriangle(Graphics2D g) {
int y = scanConverter.getTopBoundary();
double Xs1 = 0;
double Xs2 = 0;
double dxs = 0;
double r1 = 0;
double g1 = 0;
double b1 = 0;
double r2 = 0;
double g2 = 0;
double b2 = 0;
double rr = 0;
double gg = 0;
double bb = 0;
while (y <= scanConverter.getBottomBoundary()) {
GouraudTriangleScanConverter.Scan scan = scanConverter.getScan(y);
if (scan.isValid()) {
r1 = scan.rL;
g1 = scan.gL;
b1 = scan.bL;
r2 = scan.rR;
g2 = scan.gR;
b2 = scan.bR;
Xs1 = scan.left;
Xs2 = scan.right;
dxs = Xs2-Xs1;
for (int j = scan.left; j < scan.right; j++) {
rr = r2- (r2-r1)*(Xs2-j)/dxs;
gg = g2- (g2-g1)*(Xs2-j)/dxs;
bb = b2- (b2-b1)*(Xs2-j)/dxs;
if(rr > 255) rr = 255;
if(gg > 255) gg = 255;
if(bb > 255) bb = 255;
g.setColor(new Color((int)rr, (int)gg, (int)bb));
g.drawLine(j,y,j,y);
}
//g.drawLine(scan.right,y,scan.right,y);
}
y++;
}
}
public static class Scan {
public int left;
public int right;
public double rL = -1;
public double gL = -1;
public double bL = -1;
public double rR = -1;
public double gR = -1;
public double bR = -1;
/**
* Sets the left and right boundary for this scan if
* the x value is outside the current boundary.
*/
public void setBoundary(int x, double r, double g, double b) {
if (x > max)
max = x;
if (x < left) {
left = x;
rL = r;
gL = g;
bL = b;
}
if (x - 1 > right) {
right = x - 1;
rR = r;
gR = g;
bR = b;
}
}
/**
* Determines if this scan is valid (if left <= right).
*/
public boolean isValid() {
return (left <= right);
}
}
how can i apply colors to mesh.when i in
fix colors(no lighting)

Collision Bug in 2D Platformer Game

I am currently developing a 2D Mario-Like Platformer Game. I ran into a collision problem i've been trying to solve for a while now, but nothing seems to work :/
Basicly, i have a CenterLayer, which stores at which Position what kind of Tile is.
Then i have some Sprites and a Player, which should collide with these Tiles.
Because these Tiles can be triangular shaped (or any other kind of convex polygon), i decided to handle collision via SAT (Seperating Axis Theorem). This works great, but when it comes to collision with the floor where many tiles are adjacent to eachother and the sprite is moving left, it pickes the wrong edge and moves the Sprite to the right, but expected result would be moving it up. This causes the sprite to get stuck.
This is the code im currently using:
package level;
import java.awt.Polygon;
import tiles.Tile;
import sprites.*;
public class Collider {
/** Collide Sprite (or Player) with CenterLayer **/
public static void collide(Sprite s, CenterLayer c){
CollisionPolygon ps = s.getPolygon();
//Get blocks to collide with
int startXTile = (int) (s.getX() / CenterLayer.TILE_WIDTH) - 1;
int endXTile = (int) Math.ceil((s.getX() + s.getWidth()) / CenterLayer.TILE_WIDTH) + 1;
int startYTile = (int) (s.getY() / CenterLayer.TILE_HEIGHT) - 1;
int endYTile = (int) Math.ceil((s.getY() + s.getHeight()) / CenterLayer.TILE_HEIGHT) +1;
//limit to level boundaries
if(startXTile < 0) startXTile = 0;
if(endXTile > c.LEVEL_WIDTH) endXTile = c.LEVEL_WIDTH;
if(startYTile < 0) startYTile = 0;
if(endYTile > c.LEVEL_HEIGHT) endYTile = c.LEVEL_HEIGHT;
int sizeX = endXTile - startXTile;
int sizeY = endYTile - startYTile;
//loop through tiles and collide
for(int xc = 0; xc < sizeX; xc++)
for(int yc = 0; yc < sizeY; yc++){
int xblock = xc + startXTile;
int yblock = yc + startYTile;
Tile t = c.getTile(xblock, yblock);
if(t!=null){ //if tile == null --> tile is air
CollisionPolygon pt = t.getPolygon(xblock, yblock);
double[] projection = PolygonCollision(ps, pt);
//if collision has happened
if(projection[0] != 0 || projection[1] != 0){
//collide
s.moveBy(projection[0], projection[1]);
//update sprites polygon to new position
ps = s.getPolygon();
}
}
}
}
public static double dotProduct(double x, double y, double dx, double dy) {
return x * dx + y * dy;
}
// Calculate the projection of a polygon on an axis (ax, ay)
// and returns it as a [min, max] interval
public static double[] ProjectPolygon(double ax, double ay, Polygon p) {
double dotProduct = dotProduct(ax, ay, p.xpoints[0], p.ypoints[0]);
double min = dotProduct;
double max = dotProduct;
for (int i = 0; i < p.npoints; i++) {
dotProduct = dotProduct(p.xpoints[i], p.ypoints[i], ax, ay);
if (dotProduct < min) {
min = dotProduct;
} else if (dotProduct > max) {
max = dotProduct;
}
}
return new double[] { min, max };
}
// Calculate the distance between [minA, maxA](p1[0], p1[1]) and [minB, maxB](p2[0], p2[1])
// The distance will be negative if the intervals overlap
public static double IntervalDistance(double[] p1, double[] p2) {
if (p1[0] < p2[0]) {
return p2[0] - p1[1];
} else {
return p1[0] - p2[1];
}
}
public static double[] PolygonCollision(CollisionPolygon p1, CollisionPolygon p2){
boolean intersection = true;
int edgeCount1 = p1.npoints;
int edgeCount2 = p2.npoints;
double projectionX = 0;
double projectionY = 0;
double projectionDist = Double.POSITIVE_INFINITY;
//loop through all the edges
for(int edgeIndex = 0; edgeIndex < edgeCount1 + edgeCount2; edgeIndex++){
//find edges
double[] axis;
if(edgeIndex < edgeCount1){
axis = p1.getAxis(edgeIndex);
} else {
axis = p2.getAxis(edgeIndex - edgeCount1);
}
double axisX = axis[0];
double axisY = axis[1];
//System.out.println("edge: " +axisX + ", "+ axisY);
//find the projection of both polygons on current axis
final double[] proj1 = ProjectPolygon(axisX, axisY, p1);
final double[] proj2 = ProjectPolygon(axisX, axisY, p2);
//Check if polygons are intersecting, if not end loop
double id = IntervalDistance(proj1, proj2);
if(id > 0){
intersection = false;
break;
}
//Check if projection would be shorter than previous one
id = Math.abs(id);
if(id < projectionDist){
projectionDist = id;
projectionX = axisX;
projectionY = axisY;
//check if hit from "false" side
double d1x = p1.getCenterX();
double d1y = p1.getCenterY();
double d2x = p2.getCenterX();
double d2y = p2.getCenterY();
double midx = d1x - d2x;
double midy = d1y - d2y;
double dot = dotProduct(midx, midy, projectionX, projectionY);
if(dot < 0){
projectionX = -projectionX;
projectionY = -projectionY;
}
}
}
double[] result = new double[]{0, 0};
if(intersection){
//System.out.println("colliison: " + projectionX +"; "+ projectionY + ", " + projectionDist);
result[0] = projectionX * projectionDist;
result[1] = projectionY * projectionDist;
}
return result;
}
}
Any Ideas?
Tom

I had this bug too , it happens when there are parallel edges on a poly.The easy way to fix this is to project the difference between the polygon centers on the found axis.If the result is negative you would just multiply the axis by -1.
Vector aMidPoint = new Vector();
Vector bMidPoint = new Vector();
for ( Vector v : aVerts) {
aMidPoint = aMidPoint.add(v);
}
for ( Vector v : bVerts) {
bMidPoint = bMidPoint.add(v);
}
aMidPoint = aMidPoint.scalarDivision(aVerts.size());
bMidPoint = bMidPoint.scalarDivision(bVerts.size());
Vector ba = aMidPoint.subtract(bMidPoint);
if (ba.dotProduct(minOverlapVector) < 0) {
minOverlapVector = minOverlapVector.scalarMultiplication(-1);
}

Get real bounds of QuadCurve2D in Java

I want to know how to get the bounds of an QuadCurve2D. I found a method to get the bounds from a CubicCurve2D.
Using this methods is possible to change it to use QuadCurve2D?
private static void ProcessMonotonicCubic(double[] coords, double[] bbox ) {
if (bbox[0] > coords[0]) bbox[0] = coords[0];
if (bbox[1] > coords[1]) bbox[1] = coords[1];
if (bbox[2] < coords[0]) bbox[2] = coords[0];
if (bbox[3] < coords[1]) bbox[3] = coords[1];
if (bbox[0] > coords[6]) bbox[0] = coords[6];
if (bbox[1] > coords[7]) bbox[1] = coords[7];
if (bbox[2] < coords[6]) bbox[2] = coords[6];
if (bbox[3] < coords[7]) bbox[3] = coords[7];
}
/*
* Bite the piece of the cubic curve from start point till the point
* corresponding to the specified parameter then call ProcessCubic for the
* bitten part.
* Note: coords array will be changed
*/
private static void ProcessFirstMonotonicPartOfCubic(double[] coords,
double[] bbox,
double t)
{
double[] coords1 = new double[8];
double tx, ty;
coords1[0] = coords[0];
coords1[1] = coords[1];
tx = coords[2] + t*(coords[4] - coords[2]);
ty = coords[3] + t*(coords[5] - coords[3]);
coords1[2] = coords[0] + t*(coords[2] - coords[0]);
coords1[3] = coords[1] + t*(coords[3] - coords[1]);
coords1[4] = coords1[2] + t*(tx - coords1[2]);
coords1[5] = coords1[3] + t*(ty - coords1[3]);
coords[4] = coords[4] + t*(coords[6] - coords[4]);
coords[5] = coords[5] + t*(coords[7] - coords[5]);
coords[2] = tx + t*(coords[4] - tx);
coords[3] = ty + t*(coords[5] - ty);
coords[0]=coords1[6]=coords1[4] + t*(coords[2] - coords1[4]);
coords[1]=coords1[7]=coords1[5] + t*(coords[3] - coords1[5]);
ProcessMonotonicCubic(coords1, bbox);
}
/*
* Split cubic curve into monotonic in X and Y parts. Calling
* ProcessMonotonicCubic for each monotonic piece of the curve.
*
* Note: coords array could be changed
*/
private static void ProcessCubic(double[] coords, double[] bbox) {
/* Temporary array for holding parameters corresponding to the extreme
* in X and Y points
*/
double params[] = new double[4];
double eqn[] = new double[3];
double res[] = new double[2];
int cnt = 0;
/* Simple check for monotonicity in X before searching for the extreme
* points of the X(t) function. We first check if the curve is
* monotonic in X by seeing if all of the X coordinates are strongly
* ordered.
*/
if ((coords[0] > coords[2] || coords[2] > coords[4] ||
coords[4] > coords[6]) &&
(coords[0] < coords[2] || coords[2] < coords[4] ||
coords[4] < coords[6]))
{
/* Searching for extreme points of the X(t) function by solving
* dX(t)
* ---- = 0 equation
* dt
*/
eqn[2] = -coords[0] + 3*coords[2] - 3*coords[4] + coords[6];
eqn[1] = 2*(coords[0] - 2*coords[2] + coords[4]);
eqn[0] = -coords[0] + coords[2];
int nr = QuadCurve2D.solveQuadratic(eqn, res);
/* Following code also correctly works in degenerate case of
* the quadratic equation (nr = -1) because we do not need
* splitting in this case.
*/
for (int i = 0; i < nr; i++) {
if (res[i] > 0 && res[i] < 1) {
params[cnt++] = res[i];
}
}
}
/* Simple check for monotonicity in Y before searching for the extreme
* points of the Y(t) function. We first check if the curve is
* monotonic in Y by seeing if all of the Y coordinates are strongly
* ordered.
*/
if ((coords[1] > coords[3] || coords[3] > coords[5] ||
coords[5] > coords[7]) &&
(coords[1] < coords[3] || coords[3] < coords[5] ||
coords[5] < coords[7]))
{
/* Searching for extreme points of the Y(t) function by solving
* dY(t)
* ----- = 0 equation
* dt
*/
eqn[2] = -coords[1] + 3*coords[3] - 3*coords[5] + coords[7];
eqn[1] = 2*(coords[1] - 2*coords[3] + coords[5]);
eqn[0] = -coords[1] + coords[3];
int nr = QuadCurve2D.solveQuadratic(eqn, res);
/* Following code also correctly works in degenerate case of
* the quadratic equation (nr = -1) because we do not need
* splitting in this case.
*/
for (int i = 0; i < nr; i++) {
if (res[i] > 0 && res[i] < 1) {
params[cnt++] = res[i];
}
}
}
if (cnt > 0) {
/* Sorting parameter values corresponding to the extreme points
* of the curve
*/
Arrays.sort(params, 0, cnt);
/* Processing obtained monotonic parts */
ProcessFirstMonotonicPartOfCubic(coords, bbox,
(float)params[0]);
for (int i = 1; i < cnt; i++) {
double param = params[i] - params[i-1];
if (param > 0) {
ProcessFirstMonotonicPartOfCubic(coords, bbox,
/* Scale parameter to match with rest of the curve */
(float)(param/(1.0 - params[i - 1])));
}
}
}
ProcessMonotonicCubic(coords, bbox);
}
private Rectangle2D.Double getCurveBounds(CubicCurve2D curve) {
double minX = Double.MAX_VALUE, minY = Double.MAX_VALUE;
double maxX = Double.MIN_VALUE, maxY = Double.MIN_VALUE;
double [] bbox = new double[] {Double.MAX_VALUE, Double.MAX_VALUE, Double.MIN_VALUE, Double.MIN_VALUE};
ProcessCubic(new double[] {curve.getP1().getX(), curve.getP1().getY(),
curve.getCtrlP1().getX(), curve.getCtrlP1().getY(), curve.getCtrlP2().getX(),
curve.getCtrlP2().getY(), curve.getP2().getX(), curve.getP2().getY()}, bbox);
return new Rectangle2D.Double(bbox[0], bbox[1], bbox[2] - bbox[0], bbox[3] - bbox[1]);
}

"How does your use of the term "bounds" differ from the result of getBounds()?"
Get bounds 2D grab the control points, i want an rectangle that doesn't wrap the control points.
well testing a little i found another method in the same site that can be changed to use QuadCurve2D.
Here is the code:
private Rectangle2D.Double getCurveBounds(QuadCurve2D.Double curve) {
double flatness = 0.01;
PathIterator pit = curve.getPathIterator(null, flatness);
double[] coords = new double[2];
double minX = Double.MAX_VALUE, minY = Double.MAX_VALUE;
double maxX = Double.MIN_VALUE, maxY = Double.MIN_VALUE;
while(!pit.isDone()) {
int type = pit.currentSegment(coords);
switch(type) {
case PathIterator.SEG_MOVETO:
// fall through
case PathIterator.SEG_LINETO:
if(coords[0] < minX) minX = coords[0];
if(coords[0] > maxX) maxX = coords[0];
if(coords[1] < minY) minY = coords[1];
if(coords[1] > maxY) maxY = coords[1];
break;
}
pit.next();
}
return new Rectangle2D.Double(minX, minY, maxX-minX, maxY-minY);
}
hope it helps someone. :D