I was researching bulge effect and I referenced this link below:
https://math.stackexchange.com/questions/266250/explanation-of-this-image-warping-bulge-filter-algorithm
the examples image are all nxn type, what if the image is mxn.
i tried to code but it always throws exception: row out of bounds.
my code as follows:
public static Picture positionalTransform(Picture picture) {
int w = picture.width();
int h = picture.height();
double X = 0;
double Y = 0;
Picture newPic = new Picture(w,h);
for(int x=0; x<w; x++){
for(int y=0; y<h; y++){
X = x - x/2;
Y = y - y/2;
double r = Math.hypot(X, Y);
double angle = Math.atan2(X, Y);
double rn = Math.pow(r, 2.5)/0.5;
X = (int) (rn * Math.sin(angle) + x/2);
Y = (int) (rn * Math.cos(angle) + y/2);
newPic.setColor((int)X, (int)Y, picture.getColor(x, y));
}
}
picture = newPic;
return picture;
}
I want to plot a given character into a console application, shaping an ellipse.
The problem I don't know how to solve is that I only know where to draw a character once I know the angle and the radius (with Sin and Cos functions), but then I may leave gaps.
It's even more complex, because I want to "draw" a filled ellipse, not only the border.
How can I do it?
The method I want is like this:
DrawEllipse(char ch, int centerX, int centerY, int width, int height)
Just an idea: I may write a loop with an inner loop in the rectangle area of the ellipse and determine if a position is inside or outside the area of the ellipse.
This will be a reasonable approximation.
public static void DrawEllipse( char c, int centerX, int centerY, int width, int height )
{
for( int i = 0; i < width; i++ )
{
int dx = i - width / 2;
int x = centerX + dx;
int h = (int) Math.Round( height * Math.Sqrt( width * width / 4.0 - dx * dx ) / width );
for( int dy = 1; dy <= h; dy++ )
{
Console.SetCursorPosition( x, centerY + dy );
Console.Write( c );
Console.SetCursorPosition( x, centerY - dy );
Console.Write( c );
}
if( h >= 0 )
{
Console.SetCursorPosition( x, centerY );
Console.Write( c );
}
}
}
To start off, here is how to draw a filled circle (assuming a 80x25 console window). Someone else might know the maths to allow width and height parameters.
static void DrawCircle(char ch, int centerX, int centerY, int radius)
{
for(int y = 0; y < 25; y++)
{
for(int x = 0; x < 80; x++)
{
char c = ' ';
var dX = x - centerX;
var dY = y - centerY;
if(dX * dX + dY * dY < (radius * radius))
{
c = ch;
}
Console.Write(c);
}
}
}
I am trying to flip a square image inside a picture with user input variables. After running the code nothing happens at all. In other attempts I was able to make a small thin rectangle appear. How do I fix this?
public void flipHorizontal (int x, int y, int size)
{
int half = size / 2;
int x1 = x - half;
int y1 = y - half;
int x2 = x + half;
int y2 = y + half;
Pixel sourcePixel = getPixel (x1,y1);
Pixel targetPixel = getPixel (x1, y1 + half);
//loop through columns
for (x = x; x < x2; x++)
{
//loop from 0 to before mirror point
for (y = y; y < y2 + half; y++)
{
Color friend = sourcePixel.getColor();
sourcePixel = getPixel (x1,y1);
targetPixel = getPixel (x1, y1 + half);
targetPixel.setColor (friend);
}
}
}
I have coded a heightmap but it seems to lag the client. I just don't know how to increase the fps. I get about 3-6fps with the heightmap. Im using a quite large bmp for the heightmap, I think its 1024x1024. When i use a smaller on its fine, maybe im just not using the code effectively. Is there a better way to code this heightmap or did I just code it wrong. It is my first time I have worked on a heightmap. Thanks
public class HeightMap {
private final float xScale, yScale, zScale;
private float[][] heightMap;
private FloatBuffer vertices, normals, texCoords;
private IntBuffer indices;
private Vector3f[] verticesArray, normalsArray;
private int[] indicesArray;
private int width;
private int height;
public float getHeight(int x, int y) {
return heightMap[x][y] * yScale;
}
public HeightMap(String path, int resolution) {
heightMap = loadHeightmap("heightmap.bmp");
xScale = 1000f / resolution;
yScale = 8;
zScale = 1000f / resolution;
verticesArray = new Vector3f[width * height];
vertices = BufferUtils.createFloatBuffer(3 * width * height);
texCoords = BufferUtils.createFloatBuffer(2 * width * height);
for (int x = 0; x < width; x++) {
for (int y = 0; y < height; y++) {
final int pos = height * x + y;
final Vector3f vertex = new Vector3f(xScale * x, yScale * heightMap[x][y], zScale * y);
verticesArray[pos] = vertex;
vertex.store(vertices);
texCoords.put(x / (float) width);
texCoords.put(y / (float) height);
}
}
vertices.flip();
texCoords.flip();
normalsArray = new Vector3f[height * width];
normals = BufferUtils.createFloatBuffer(3 * width * height);
final float xzScale = xScale;
for (int x = 0; x < width; ++x) {
for (int y = 0; y < height; ++y) {
final int nextX = x < width - 1 ? x + 1 : x;
final int prevX = x > 0 ? x - 1 : x;
float sx = heightMap[nextX][y] - heightMap[prevX][y];
if (x == 0 || x == width - 1) {
sx *= 2;
}
final int nextY = y < height - 1 ? y + 1 : y;
final int prevY = y > 0 ? y - 1 : y;
float sy = heightMap[x][nextY] - heightMap[x][prevY];
if (y == 0 || y == height - 1) {
sy *= 2;
}
final Vector3f normal = new Vector3f(-sx * yScale, 2 * xzScale, sy * yScale).normalise(null);
normalsArray[height * x + y] = normal;
normal.store(normals);
}
}
normals.flip();
indicesArray = new int[6 * (height - 1) * (width - 1)];
indices = BufferUtils.createIntBuffer(6 * (width - 1) * (height - 1));
for (int i = 0; i < width - 1; i++) {
for (int j = 0; j < height - 1; j++) {
int pos = (height - 1) * i + j;
indices.put(height * i + j);
indices.put(height * (i + 1) + j);
indices.put(height * (i + 1) + (j + 1));
indicesArray[6 * pos] = height * i + j;
indicesArray[6 * pos + 1] = height * (i + 1) + j;
indicesArray[6 * pos + 2] = height * (i + 1) + (j + 1);
indices.put(height * i + j);
indices.put(height * i + (j + 1));
indices.put(height * (i + 1) + (j + 1));
indicesArray[6 * pos + 3] = height * i + j;
indicesArray[6 * pos + 4] = height * i + (j + 1);
indicesArray[6 * pos + 5] = height * (i + 1) + (j + 1);
}
}
indices.flip();
}
private float[][] loadHeightmap(String fileName) {
try {
BufferedImage img = ImageIO.read(ResourceLoader.getResourceAsStream(fileName));
width = img.getWidth();
height = img.getHeight();
float[][] heightMap = new float[width][height];
for (int x = 0; x < width; x++) {
for (int y = 0; y < height; y++) {
heightMap[x][y] = 0xFF & img.getRGB(x, y);
}
}
return heightMap;
} catch (IOException e) {
System.out.println("Nincs meg a heightmap!");
return null;
}
}
public void render() {
glEnableClientState(GL_NORMAL_ARRAY);
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glNormalPointer(0, normals);
glVertexPointer(3, 0, vertices);
glTexCoordPointer(2, 0, texCoords);
glDrawElements(GL_TRIANGLE_STRIP, indices);
glDisableClientState(GL_NORMAL_ARRAY);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);
glDisableClientState(GL_VERTEX_ARRAY);
}
}
Sorry to bring up an old topic, however i see a lot of people ask this:
Use a display list, instead of re-making the heightmap every time.
TheCodingUniverse has a good tutorial on how to do this.
I have a standalone Java application below that is:
Generating a random line
Applied to a 2D grid where each cell value is the distance along the line perpindicular to the line
Finds the rise/run and attempts to calculate the original linear equation from the grid
Applies new line to another grid and prints out the greatest difference compared to the first grid
I expected the two grids to have identical values. The gradient lines may be different since the lines can extend outside the area of the grid, but should be similar and in two cases identical.
So is the problem a poor understanding of math, a bug in my code or a misunderstanding of floating point values?
import java.awt.geom.Point2D;
import java.awt.geom.Line2D;
import java.util.Iterator;
import java.util.ArrayList;
public final class TestGradientLine {
private static int SIZE = 3;
public TestGradientLine() {
super();
}
//y = mx + b
//b = y - mx
//m is rise / run = gradient
//width and height of bounding box
//for a box 10x10 then width and height are 9,9
public static Line2D getGradientLine(double run, double rise, double width, double height, double x, double y) {
if (run == 0 && rise == 0) {
return new Line2D.Double(x, y, x + width, y + height);
}
//calculate hypotenuse
//check for a vertical line
if (run == 0) {
return new Line2D.Double(x, y, x, y + height);
}
//check for a horizontal line
if (rise == 0) {
return new Line2D.Double(x, y, x + width, y);
}
//calculate gradient
double m = rise / run;
Point2D start;
Point2D opposite;
if (m < 0) {
//lower left
start = new Point2D.Double(x, y + height);
opposite = new Point2D.Double(x + width, y);
} else {
//upper left
start = new Point2D.Double(x, y);
opposite = new Point2D.Double(x + width, y + height);
}
double b = start.getY() - (m * start.getX());
//now calculate another point along the slope
Point2D next = null;
if (m > 0) {
next = new Point2D.Double(start.getX() + Math.abs(run), start.getY() + Math.abs(rise));
} else {
if (rise < 0) {
next = new Point2D.Double(start.getX() + run, start.getY() + rise);
} else {
next = new Point2D.Double(start.getX() - run, start.getY() - rise);
}
}
final double actualWidth = width;
final double actualHeight = height;
final double a = Math.sqrt((actualWidth * actualWidth) + (actualHeight * actualHeight));
extendLine(start, next, a);
Line2D gradientLine = new Line2D.Double(start, next);
return gradientLine;
}
public static void extendLine(Point2D p0, Point2D p1, double toLength) {
final double oldLength = p0.distance(p1);
final double lengthFraction =
oldLength != 0.0 ? toLength / oldLength : 0.0;
p1.setLocation(p0.getX() + (p1.getX() - p0.getX()) * lengthFraction,
p0.getY() + (p1.getY() - p0.getY()) * lengthFraction);
}
public static Line2D generateRandomGradientLine(int width, int height) {
//so true means lower and false means upper
final boolean isLower = Math.random() > .5;
final Point2D start = new Point2D.Float(0, 0);
if (isLower) {
//change origin for lower left corner
start.setLocation(start.getX(), height - 1);
}
//radius of our circle
double radius = Math.sqrt(width * width + height * height);
//now we want a random theta
//x = r * cos(theta)
//y = r * sin(theta)
double theta = 0.0;
if (isLower) {
theta = Math.random() * (Math.PI / 2);
} else {
theta = Math.random() * (Math.PI / 2) + (Math.PI / 2);
}
int endX = (int)Math.round(radius * Math.sin(theta));
int endY = (int)Math.round(radius * Math.cos(theta)) * -1;
if (isLower) {
endY = endY + (height - 1);
}
final Point2D end = new Point2D.Float(endX, endY);
extendLine(start, end, radius);
return new Line2D.Float(start, end);
}
public static Point2D getNearestPointOnLine(Point2D end, Line2D line) {
final Point2D point = line.getP1();
final Point2D start = line.getP2();
double a = (end.getX() - point.getX()) * (start.getX() - point.getX()) + (end.getY() - point.getY()) * (start.getY() - point.getY());
double b = (end.getX() - start.getX()) * (point.getX() - start.getX()) + (end.getY() - start.getY()) * (point.getY() - start.getY());
final double x = point.getX() + ((start.getX() - point.getX()) * a)/(a + b);
final double y = point.getY() + ((start.getY() - point.getY()) * a)/(a + b);
final Point2D result = new Point2D.Double(x, y);
return result;
}
public static double length(double x0, double y0, double x1, double y1) {
final double dx = x1 - x0;
final double dy = y1 - y0;
return Math.sqrt(dx * dx + dy * dy);
}
public static void main(String[] args) {
final Line2D line = generateRandomGradientLine(SIZE, SIZE);
System.out.println("we're starting with line " + line.getP1() + " " + line.getP2());
double[][] region = new double[SIZE][SIZE];
//load up the region with data from our generated line
for (int x = 0; x < SIZE; x++) {
for (int y = 0; y < SIZE; y++) {
final Point2D point = new Point2D.Double(x, y);
final Point2D nearestPoint = getNearestPointOnLine(point, line);
if (nearestPoint == null) {
System.err.println("uh -oh!");
return;
}
final double distance = length(line.getP1().getX(),
line.getP1().getY(), nearestPoint.getX() + 1,
nearestPoint.getY() + 1);
region[x][y] = distance;
}
}
//now figure out what our line is from the region
double runTotal = 0;
double riseTotal = 0;
double runCount = 0;
double riseCount = 0;
for (int x = 0; x < SIZE; x++) {
for (int y = 0; y < SIZE; y++) {
if (x < SIZE - 1) {
runTotal += region[x + 1][y] - region[x][y];
runCount++;
}
if (y < SIZE - 1) {
riseTotal += region[x][y + 1] - region[x][y];
riseCount++;
}
}
}
double run = 0;
if (runCount > 0) {
run = runTotal / runCount;
}
double rise = 0;
if (riseCount > 0) {
rise = riseTotal / riseCount;
}
System.out.println("rise is " + rise + " run is " + run);
Line2D newLine = getGradientLine(run, rise, SIZE - 1, SIZE - 1, 0, 0);
System.out.println("ending with line " + newLine.getP1() + " " + newLine.getP2());
double worst = 0.0;
int worstX = 0;
int worstY = 0;
for (int x = 0; x < SIZE; x++) {
for (int y = 0; y < SIZE; y++) {
final Point2D point = new Point2D.Double(x, y);
final Point2D nearestPoint = getNearestPointOnLine(point, newLine);
if (nearestPoint == null) {
System.err.println("uh -oh!");
return;
}
final double distance = length(line.getP1().getX(),
line.getP1().getY(), nearestPoint.getX() + 1,
nearestPoint.getY() + 1);
final double diff = Math.abs(region[x][y] - distance);
if (diff > worst) {
worst = diff;
worstX = x;
worstY = y;
}
}
}
System.out.println("worst is " + worst + " x: " + worstX + " y: " + worstY);
}
}
I think I have fixed your program.
a) I took out the integer cast.
b) I removed all the 'x + 1' and 'x - 1' fudges you had used.
I think when dealing with floats and doubles, subtracting '1' from the end of a line is a No-No! What is 1 anyway? - it's ok to do this just before you plot it on the screen once it's an integer. But not while calculating! line length is a 'zero-based' quantity.
This version returns approx 4E-16 always.
import java.awt.geom.Point2D;
import java.awt.geom.Line2D;
import java.awt.geom.QuadCurve2D;
import java.util.Iterator;
import java.util.ArrayList;
public final class TestGradientLine {
private static int SIZE = 3;
public TestGradientLine() {
super();
}
//y = mx + b
//b = y - mx
//m is rise / run = gradient
//width and height of bounding box
//for a box 10x10 then width and height are 9,9
public static Line2D getGradientLine(double run, double rise, double width, double height, double x, double y) {
if (run == 0 && rise == 0) {
return new Line2D.Double(x, y, x + width, y + height);
}
//calculate hypotenuse
//check for a vertical line
if (run == 0) {
return new Line2D.Double(x, y, x, y + height);
}
//check for a horizontal line
if (rise == 0) {
return new Line2D.Double(x, y, x + width, y);
}
//calculate gradient
double m = rise / run;
Point2D start;
Point2D opposite;
if (m < 0) {
//lower left
start = new Point2D.Double(x, y + height);
opposite = new Point2D.Double(x + width, y);
} else {
//upper left
start = new Point2D.Double(x, y);
opposite = new Point2D.Double(x + width, y + height);
}
double b = start.getY() - (m * start.getX());
//now calculate another point along the slope
Point2D next = null;
if (m > 0) {
next = new Point2D.Double(start.getX() + Math.abs(run), start.getY() + Math.abs(rise));
} else {
if (rise < 0) {
next = new Point2D.Double(start.getX() + run, start.getY() + rise);
} else {
next = new Point2D.Double(start.getX() - run, start.getY() - rise);
}
}
final double actualWidth = width;
final double actualHeight = height;
final double a = Math.sqrt((actualWidth * actualWidth) + (actualHeight * actualHeight));
extendLine(start, next, a);
Line2D gradientLine = new Line2D.Double(start, next);
return gradientLine;
}
public static void extendLine(Point2D p0, Point2D p1, double toLength) {
final double oldLength = p0.distance(p1);
final double lengthFraction =
oldLength != 0.0 ? toLength / oldLength : 0.0;
p1.setLocation(p0.getX() + (p1.getX() - p0.getX()) * lengthFraction,
p0.getY() + (p1.getY() - p0.getY()) * lengthFraction);
}
public static Line2D generateRandomGradientLine(int width, int height) {
//so true means lower and false means upper
final boolean isLower = Math.random() > .5;
final Point2D start = new Point2D.Float(0, 0);
if (isLower) {
//change origin for lower left corner
start.setLocation(start.getX(), height );
}
//radius of our circle
double radius = Math.sqrt(width * width + height * height);
//now we want a random theta
//x = r * cos(theta)
//y = r * sin(theta)
double theta = 0.0;
if (isLower) {
theta = Math.random() * (Math.PI / 2);
} else {
theta = Math.random() * (Math.PI / 2) + (Math.PI / 2);
}
float endX = (float)(radius * Math.sin(theta));
float endY = (float)(radius * Math.cos(theta)) * -1;
if (isLower) {
endY = endY + (height );
}
final Point2D end = new Point2D.Float(endX, endY);
extendLine(start, end, radius);
return new Line2D.Float(start, end);
}
public static Point2D getNearestPointOnLine(Point2D end, Line2D line) {
final Point2D point = line.getP1();
final Point2D start = line.getP2();
double a = (end.getX() - point.getX()) * (start.getX() - point.getX()) + (end.getY() - point.getY()) * (start.getY() - point.getY());
double b = (end.getX() - start.getX()) * (point.getX() - start.getX()) + (end.getY() - start.getY()) * (point.getY() - start.getY());
final double x = point.getX() + ((start.getX() - point.getX()) * a)/(a+b);
final double y = point.getY() + ((start.getY() - point.getY()) * a)/(a+b);
final Point2D result = new Point2D.Double(x, y);
return result;
}
public static double length(double x0, double y0, double x1, double y1) {
final double dx = x1 - x0;
final double dy = y1 - y0;
return Math.sqrt(dx * dx + dy * dy);
}
public static void main(String[] args) {
final Line2D line = generateRandomGradientLine(SIZE, SIZE);
System.out.println("we're starting with line " + line.getP1() + " " + line.getP2());
double[][] region = new double[SIZE][SIZE];
//load up the region with data from our generated line
for (int x = 0; x < SIZE; x++) {
for (int y = 0; y < SIZE; y++) {
final Point2D point = new Point2D.Double(x, y);
final Point2D nearestPoint = getNearestPointOnLine(point, line);
if (nearestPoint == null) {
System.err.println("uh -oh!");
return;
}
final double distance = length(line.getP1().getX(),
line.getP1().getY(), nearestPoint.getX() ,
nearestPoint.getY() );
region[x][y] = distance;
}
}
//now figure out what our line is from the region
double runTotal = 0;
double riseTotal = 0;
double runCount = 0;
double riseCount = 0;
for (int x = 0; x < SIZE; x++) {
for (int y = 0; y < SIZE; y++) {
if (x < SIZE - 1) {
runTotal += region[x + 1][y] - region[x][y];
runCount++;
}
if (y < SIZE - 1) {
riseTotal += region[x][y + 1] - region[x][y];
riseCount++;
}
}
}
double run = 0;
if (runCount > 0) {
run = runTotal / runCount;
}
double rise = 0;
if (riseCount > 0) {
rise = riseTotal / riseCount;
}
System.out.println("rise is " + rise + " run is " + run);
Line2D newLine = getGradientLine(run, rise, SIZE, SIZE , 0, 0);
System.out.println("ending with line " + newLine.getP1() + " " + newLine.getP2());
double worst = 0.0;
int worstX = 0;
int worstY = 0;
for (int x = 0; x < SIZE; x++) {
for (int y = 0; y < SIZE; y++) {
final Point2D point = new Point2D.Double(x, y);
final Point2D nearestPoint = getNearestPointOnLine(point, newLine);
if (nearestPoint == null) {
System.err.println("uh -oh!");
return;
}
final double distance = length(line.getP1().getX(),
line.getP1().getY(), nearestPoint.getX() ,
nearestPoint.getY() );
final double diff = Math.abs(region[x][y] - distance);
if (diff > worst) {
worst = diff;
worstX = x;
worstY = y;
}
}
}
System.out.println("worst is " + worst + " x: " + worstX + " y: " + worstY);
}
}
why do you multiply by -1 at the end of this line?
int endY = (int)Math.round(radius * Math.cos(theta)) * -1;
this means that endY is always negative except radius is below 0. (cosinus always returns positive value)
is this intended or am i getting something wrong?
regards
You probably misunderstand float and/or double. This is a common problem with any language that implements the ieee spec for floats and doubles, which Java, C, C++ and just about every other language does.
Essentially
double val = 0;
for(int i=0;i<10;i++) {
val+=0.1;
System.out.println(val);
}
results in
0.1
0.2
0.30000000000000004
0.4
0.5
0.6
0.7
0.7999999999999999
0.8999999999999999
0.9999999999999999
And sometimes even worse. Either use BigDecimal, which alleviates a lot of the problem, or use integers.