Develop Reference

I want to display text using Android and OpenGL

I want to display a text within a OpenGL Android Application. I have tried the code below, but, nothing is displayed. Some other attempts have been tried but none was displayed either. Could anyone help me with some advice?
String aText = "Prueba";
float aFontSize = 100;
int[] textureId = new int[1];
Paint textPaint = new Paint();
textPaint.setTextSize(aFontSize);
textPaint.setFakeBoldText(false);
textPaint.setAntiAlias(true);
textPaint.setARGB(255, 255, 255, 255);
// If a hinting is available on the platform you are developing, you should enable it (uncomment the line below).
//textPaint.setHinting(Paint.HINTING_ON);
textPaint.setSubpixelText(true);
textPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SCREEN));
float realTextWidth = textPaint.measureText(aText);
// Creates a new mutable bitmap, with 128px of width and height
int bitmapWidth = (int)(realTextWidth + 2.0f);
int bitmapHeight = (int)aFontSize + 2;
Bitmap textBitmap = Bitmap.createBitmap(bitmapWidth, bitmapHeight, Bitmap.Config.ARGB_8888);
textBitmap.eraseColor(Color.argb(0, 255, 255, 255));
// Creates a new canvas that will draw into a bitmap instead of rendering into the screen
Canvas bitmapCanvas = new Canvas(textBitmap);
// Set start drawing position to [1, base_line_position]
// The base_line_position may vary from one font to another but it usually is equal to 75% of font size (height).
bitmapCanvas.drawText(aText, 1, 1.0f + aFontSize * 0.75f, textPaint);
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureId[0]);
// Assigns the OpenGL texture with the Bitmap
GLUtils.texImage2D(GLES20.GL_TEXTURE_2D, 0, GLES20.GL_RGBA, textBitmap, 0);
// Free memory resources associated with this texture
textBitmap.recycle();
// After the image has been subloaded to texture, regenerate mipmaps
GLES20.glGenerateMipmap(GLES20.GL_TEXTURE_2D);

Applying Reflection to DropShadow Effect in JavaFX

Using JavaFX, I am trying to draw text onto a canvas with a drop shadow and a reflection effect chained together.
The following code will display red text that is reflected, and then a drop shadow is applied to the original and reflected text.
Canvas canvas = new Canvas(400,400);
GraphicsContext context = canvas.getGraphicsContext2D();
context.setFont( new Font("Arial Bold", 48) );
context.setFill(Color.RED);
DropShadow shadow = new DropShadow(6, 2, 2, Color.BLACK);
Reflection reflect = new Reflection(10, 1.0, 1.0, 0.0);
shadow.setInput(reflect);
context.setEffect(shadow);
context.fillText("Hello, world!", 100,100);
However, the drop shadow appears "backwards" in the reflection, because the shadow needs to be applied first for a realistic effect. I tried to accomplish this by reversing the order in which the effects are applied, by changing the setInput and setEffect lines of code from above as follows:
reflect.setInput(shadow);
context.setEffect(reflect);
However, the result is that only the reflection is applied; I can not see any drop shadow at all.
Why isn't the drop shadow being applied / not visible?
How can I rewrite this code to achieve the desired effect (only using composition of effects, if possible)?

I don't know if what you say can be achieved by using GraphicsContext with standard API, so other answers are welcome. However, this might be a temporary workaround, provided that it is actually what you needed. The shadow is applied first and then the image is copied pixel by pixel to imitate the reflection effect. Please see the screenshot below: (original - on the left, new - on the right).
Full working example is attached below. It requires some tweaking to get a general solution but there should be enough to start with.
import javafx.application.Application;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.effect.DropShadow;
import javafx.scene.effect.Effect;
import javafx.scene.image.WritableImage;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.text.Font;
import javafx.scene.text.Text;
import javafx.stage.Stage;
public class FXApp extends Application {
private Parent createContent() {
Canvas canvas = new Canvas(400,400);
Font font = new Font("Arial Bold", 48);
Color fill = Color.RED;
DropShadow shadow = new DropShadow(6, 2, 2, Color.BLACK);
fillTextWithReflection(canvas.getGraphicsContext2D(), "Hello, world!", 100, 100, font, fill, shadow);
return new Pane(canvas);
}
private void fillTextWithReflection(GraphicsContext g, String text, double textX, double textY, Font font, Color fill, Effect effect) {
Text t = new Text(text);
t.setFont(font);
// 5 px margin
Canvas tmpCanvas = new Canvas(t.getLayoutBounds().getWidth() + 5, t.getLayoutBounds().getHeight() + 5);
// set configuration
GraphicsContext tmpContext = tmpCanvas.getGraphicsContext2D();
tmpContext.setFont(font);
tmpContext.setFill(fill);
tmpContext.setEffect(effect);
// draw on temporary context
tmpContext.fillText(text, 0, font.getSize());
// take a snapshot of the text
WritableImage snapshot = tmpCanvas.snapshot(null, null);
int w = (int)snapshot.getWidth();
int h = (int)snapshot.getHeight();
WritableImage reflected = new WritableImage(w, h);
// make an 'inverted' copy
for (int y = 0; y < h; y++) {
// imitate fading out of reflection
double alpha = y / (h - 1.0);
for (int x = 0; x < w; x++) {
Color oldColor = snapshot.getPixelReader().getColor(x, y);
Color newColor = Color.color(oldColor.getRed(), oldColor.getGreen(), oldColor.getBlue(), alpha);
reflected.getPixelWriter().setColor(x, h - 1 - y, newColor);
}
}
// draw on the actual context
// images are drawn from x, y top-left but text is filled from x, y + h
// hence corrections
// this can be replaced with actual fillText() call if required
g.drawImage(snapshot, textX, textY - font.getSize());
g.drawImage(reflected, textX, textY + h - font.getSize());
}
#Override
public void start(Stage stage) throws Exception {
stage.setScene(new Scene(createContent()));
stage.show();
}
}

Import image in Java

Im making a simple pong game and want to put a texture over my paddle but I don't know how to import image into my game. I tried doing in like here in 3rd example but it doesn't work:
Image myImage = getImage(getCodeBase(), "texture.png");
g.drawImage(myImage, 0, 0 , 10, 120, this);
g cannot be resolved
Here's some code:
public void run(){
Image myImage = getImage(getCodeBase(), "texture.png");
g.drawImage(myImage, 0, 0 , 10, 120, this);
GOval ball = makeBall();
add(ball);
GRect paddleLeft = makePaddle();
GRect paddleRight = makePaddle();
add(paddleLeft);
add(paddleRight);
bounce(ball, paddleLeft, paddleRight);
}
public static GRect makePaddle(){
GRect result = new GRect(0,0,WIDTH,HEIGHT);
result.setFilled(true);
result.setColor(Color.BLACK);
return result;
}
the texture.png is for the paddles
EDIT:
I got the texture to load, but I can't make it move with the paddles, I don't know why
WIDTH is width of the paddle, getWidth() - window. I guess the code I use to move the paddle should work for the texture but it doesnt
with the image.sendToFront() player's paddle's texture works, but the AI's doesn't
if(mouseY<getHeight()-HEIGHT){ // Player
paddleLeft.setLocation(WIDTH,mouseY);
image.setLocation(WIDTH,mouseY);
image.sendToFront();
}
else{
paddleLeft.setLocation(WIDTH,getHeight()-HEIGHT);
image.setLocation(WIDTH,getHeight()-HEIGHT);
image.sendToFront();
}
if(ball.getY()<getHeight()-paddleRight.getHeight()){ // AI
paddleRight.setLocation(getWidth()-2*WIDTH,ball.getY());
image2.setLocation(getWidth()-2*WIDTH,ball.getY());
image2.sendToFront();
}
else
paddleRight.setLocation(getWidth()-2*WIDTH,getHeight()-paddleRight.getHeight());
image2.setLocation(getWidth()-2*WIDTH,getHeight()-paddleRight.getHeight());
image2.sendToFront();

It seems like you are using a library from http://cs.stanford.edu/people/eroberts/jtf/ (based on the GRect class etc).
And it seems like you should be able to use a GImage as well. So the code could roughly look like
Image myImage = getImage(getCodeBase(), "texture.png");
//g.drawImage(myImage, 0, 0 , 10, 120, this);
GImage image = new GImage(myImage);
add(image);

Libgdx: Different positions using BitmapFont

I encountered a problem within my (very) simple project. When I draw text, it is displayed in a different position (and appareantly with different size) between Android (Samsung Galaxy S Advance) and Desktop.
In my renderer class I have:
private OrthographicCamera cam;
public final int WIDTH = 320;
public final int HEIGHT = 480;
private ShapeRenderer debugRenderer = new ShapeRenderer();
private SpriteBatch batch = new SpriteBatch();
private BitmapFont font;
And in my constructor:
MyClass(){
this.cam = new OrthographicCamera(WIDTH, HEIGHT);
this.cam.position.set(WIDTH/2, HEIGHT/2, 0);
this.cam.update();
font = new BitmapFont(Gdx.files.internal("data/fonts/font.fnt"));
font.setColor(Color.RED);
}
Finally, the render function:
public void render() {
// For each block y use this code:
// debugRenderer.begin(ShapeType.Filled);
// Rectangle rect = block.getBounds();
// debugRenderer.rect(rect.x, rect.y, rect.width, rect.height);
// debugRenderer.end();
// And then I draw my text:
batch.begin();
font.draw(batch, "Score: " + world.getScore(), 50,50)
batch.end();
}
All block dimensions are in absolute numbers (not relative to any variable like stage.getWidth() or something like that).
The result in Desktop is the following:
While in Android I have:
As you may see, blocks have the same distribution along the screen (in terms of % of screen covered), while text doesn't. It doesn't start in the same place and doesn't have the same height.
Does anybody know what I could be doing wrong?
Just in case it helps, blocks bounds are:
XPos: 45 * i
YPos: 45 * j
SizeX: 32
SizeY: 32
EDIT: Another consideration, the font I'm using is extracted from: https://github.com/libgdx/libgdx/tree/master/demos/superjumper

After this.cam.update(); do you do -
batch.setProjectionMatrix(this.cam.combined);
debugRenderer.setProjectionMatrix(this.cam.combined);

x-y plot and rotating text of axis-label

The code below plots some simple x-y data, but it has two problems that I do not know how to fix.
First, it plots negative values for some of the data points, which means lines extending southward below the x-axis. Since the data points are selected at random, you may have to resize the frame a bit in order to view new random numbers to be plotted in a way that shows this bug. All data values will be positive, so I want all deflections to project northward above the blue bottom marker line, and I need to make sure that no deflections extend southward below the blue bottom marker line.
Second, the y-axis label takes up too much real estate on the screen. It needs to be rotated -90 degrees. However, all the examples I have seen for this involve rotating the entire panel using a graphics2d object. I do not want to rotate the entire panel. Instead, I just want to rotate the text of the y-axis label.
Can anyone show me how to change the code below to fix these two specific problems?
The code is in the following two files:
GUI.java
import java.awt.*;
import javax.swing.*;
class GUI{
GUI() {
// Create a new JFrame container.
JFrame jfrm = new JFrame("X-Y Plot");
// Specify FlowLayout for the layout manager.
jfrm.getContentPane().setLayout(new FlowLayout());
int frameHeight = 400;
int frameWidth = 300;
// Give the frame an initial size.
jfrm.setSize(frameWidth, frameHeight);
// Terminate the program when the user closes the application.
jfrm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Create a text-based label.
JVertLabel myVLabel = new JVertLabel("y-axis label");
int width = myVLabel.WIDTH;
PaintPanel myPP = new PaintPanel(frameWidth-width-50-20,frameHeight-70);
jfrm.add(myPP);
jfrm.add(myVLabel);// Add the label to the frame.
// Display the frame.
jfrm.setVisible(true);
}
public static void main(String args[]) {
// Create the frame on the event dispatching thread.
SwingUtilities.invokeLater(new Runnable() {public void run(){new GUI();}});
}
public class JVertLabel extends JComponent {
private String text;
public JVertLabel(String s) {
text = s;
}//constructor
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.rotate(Math.toRadians(-90));
g2d.drawString(text, 0, 0);
}
}
}
PaintPanel.java
import java.awt.*;
import javax.swing.*;
import java.util.*;
class PaintPanel extends JPanel {
Insets ins; // holds the panel's insets
Random rand; // used to generate random numbers
PaintPanel(int w, int h) {
setOpaque(true);// Ensure that panel is opaque.
setPreferredSize(new Dimension(w, h));// Set preferred dimension as specfied.
rand = new Random();
}
protected void paintComponent(Graphics g) {// Override paintComponent() method.
super.paintComponent(g);// Always call superclass method first.
int height = getHeight();// Get height of component.
int width = getWidth();// Get width of component.
ins = getInsets();// Get the insets.
// Get dimensions of text
Graphics2D g2d = (Graphics2D) g;
Font font = new Font("Serif", Font.PLAIN, 12);
FontMetrics fontMetrics = g2d.getFontMetrics();
String xString = ("x-axis label");
int xStrWidth = fontMetrics.stringWidth(xString);
int xStrHeight = fontMetrics.getHeight();
String yString = "y-axis-label";
int yStrWidth = fontMetrics.stringWidth(yString);
int yStrHeight = fontMetrics.getHeight();
int leftStartPlotWindow = ins.left + 5 + yStrWidth;
int hPad = 3;
// Fill panel by plotting random data in a bar graph.
for (int i = leftStartPlotWindow + hPad; i <= width - leftStartPlotWindow - hPad + yStrWidth + 1; i += 4) {
int h = Math.abs(rand.nextInt(height - ins.bottom));//Get rand# betw/0 and max height of drawing area.
// If generated value w/in or too close to border, change it to just outside border.
if (h <= ins.top) {
h = ins.top + 1;
}
g.drawLine(i, Math.abs(height - ins.bottom - xStrHeight - 5), i, h);// Draw a line that represents data.
}
g.setColor(Color.blue);
g.drawRect(leftStartPlotWindow, ins.bottom + 2, width - leftStartPlotWindow - ins.right - hPad, height - xStrHeight - 6);
g.setColor(Color.red);
g.drawRect(ins.left, ins.bottom, width - ins.left - 1, height - ins.bottom - 1);
g.drawString(xString, (width / 2) - (xStrWidth / 2), height - ins.bottom - 6);
g.drawString(yString, ins.left, height / 2);
}
}

All data values will be positive, so I want all deflections to project northward above the blue bottom marker line, and I need to make sure that no deflections extend southward below the blue bottom marker line.
You need to calculate the random height so that all values fit into the space available. So the calculation would be something like:
int randomHeight = panelHeight - offset.top - offset.bottom - heightForTheXAxisText;
Then you don't have to worry about negative values or the top of the line extending outside the bounds of the panel.
all the examples I have seen for this involve rotating the entire panel using a graphics2d object. I do not want to rotate the entire panel. Instead, I just want to rotate the text of the y-axis label.
Set the rotation of the Graphics object, the draw the text, then restore the rotation of the Graphics object back to 0.
Or, you create create a new Graphcis object from the current Graphics object, then apply the rotation, draw the text and then dispose of the temporaray Graphics object.

JFreeChart addresses both issues by default, as shown in this example.
In your example,
You'll have to create the data model before trying to render it. Then you can scan it for min and max to determine the limits of your range axis. List<Double> may be a suitable choice.
You can rotate the range label by altering the graphics context's AffineTransform, as shown in RotateText.