Develop Reference

libGDX Draw viewport only partly while cutting off the rest

This problem seemed very obvious for me to solve, but whatever I try, it doesn't work. What I'm trying to do is to incorporate a mini-version of my PlayScreen in a ScrollPane as a tutorial where you can read text and try it out immediately.
Because I didn't find any better solution to add this to the Table inside the ScrollPane, I edited the draw() method of the PlayScreen to take the ScrollPane.getScrollPercentY() and offset the camera of the PlayScreen accordingly.
What I want to do now is to only render only part of the viewport that would be normally visible in the real game. Subsequently, I want to be able to control the size and position of this "window".
I also want to be able to resize and move the content, while cutting off the edges that are not visible to the camera. This is what I tried inside the PlayScreenDraw:
public void draw(final float yOffset,
final int xTiles,
final int yTiles) {
view.getCamera().position.y = yTiles / 2f - yOffset * yTiles / HEIGHT; // HEIGHT = 800
view.getCamera().position.x = xTiles / 2f;
view.setWorldSize(xTiles, yTiles); //Do i even need to change the world size?
b.setProjectionMatrix(view.getCamera().combined);
b.begin();
...
b.end();
view.update(Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
}
What this gives me, in terms of the picture above, is this
How do I need to change the viewport and/or the camera? Btw., this is how i set the two up:
cam = new OrthographicCamera();
cam.setToOrtho(false, WIDTH, HEIGHT); // WIDTH = 8, HEIGHT = 16
batch.setProjectionMatrix(cam.combined);
view = new FitViewport(WIDTH, HEIGHT, cam);

The Pixmap class can help you achieve what you want since you stated that you wanted to "cut off" the parts outside of the green selection box.
You need to render what the camera sees to an FBO and then get the pixmap from the FBO itself.
Framebuffer Objects are OpenGL Objects, which allow for the creation of user-defined Framebuffers. With them, one can render to non-Default Framebuffer locations, and thus render without disturbing the main screen.
-- OpenGL wiki
// Construct an FBO and keep a reference to it. Remember to dispose of it.
FrameBuffer fbo = new FrameBuffer(Format.RGBA8888, width, height, false);
public void render() {
//Start rendering to the fbo.
fbo.begin();
//From the camera's perspective.
batch.setProjectionMatrix(camera.combined);
batch.begin();
//Draw whatever you want to draw with the camera.
batch.end();
// Finished drawing, get pixmap.
Pixmap pixmap = ScreenUtils.getFrameBufferPixmap(0, 0, width, height);
//Stop drawing to your fbo.
fbo.end();
}
After getting the pixmap you can iterate through the pixels and set the alpha of the pixels outside your green selection window to 0 making them invisible or "cutting them off"

Move a shape to place where my finger is touched

#Override
public void create()
{
batch = new SpriteBatch();
shape = new ShapeRenderer();
velocity = new Vector2(100, 0);
position = new Rectangle(0, 5, 100, 100);
font = new BitmapFont();
font.setColor(Color.BLACK);
font.getData().scale(3f);
camera = new OrthographicCamera();
confCamera();
}
#Override
public void render()
{
if(Gdx.input.isTouched())
position.x = Gdx.input.getX() - position.width/2;
position.y = (Gdx.input.getY() - position.height/2);
shape.begin(ShapeRenderer.ShapeType.Filled);
shape.setColor(Color.BLACK);
shape.rect(position.x, position.y, position.width, position.height);
shape.end();
}
It's a simple code, but I'm not undestanding Y axis, my shape moves like a mirror. If I touch on top, my shape goes to bottom. If I touch on bottom, my shape goes to top. How to fix it?

LibGDX (by default) for rendering uses coordinate system where 0 is at bottom of the screen and the more you go up Y coordinate grows.
Also, when you read input coordinates (touches, moves...) you get screen coordinates, but when you render your graphics you are using "world" coordinates. They are in 2 different coordinate system so to convert from screen to world you have to use camera.unproject() call. Should be like:
Vector3 touchPos = new Vector3(Gdx.input.getX(), Gdx.input.getY(), 0);
camera.unproject(touchPos);
and then use touchPos.x and touchPos.y.
The similar question is asked here so you can find more answers there:
Using unProject correctly in Java Libgdx

Sprite image appears stretched and quality is poor, can't get in correct position GDXLib

I am quite new to programming so bear with me here...
I am making a 2d basic game just to practice programming in android studio and can't get my sprite to the correct position on the screen. Also when I draw the sprite it appears stretched and the quality is very poor. Any help is appreciated!
public class MyGdxGame extends ApplicationAdapter {
SpriteBatch batch;
Texture background;
Texture ball;
#Override
public void create () {
batch = new SpriteBatch();
background = new Texture("gamebackground.png");
ball = new Texture("ball2.png");
}
#Override
public void render () {
batch.begin();
batch.draw(background, 0,0, Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
batch.draw(ball, 0,0, Gdx.graphics.getWidth() / 2, Gdx.graphics.getHeight() / 2);
batch.end();
}

You need to keep the original width/height ratio:
instead of scaling it to half the screen size, define your scaling like that:
float scaleFactor = 2.0f;
batch.draw(ball, 0,0, ball.getWidth()*scaleFactor, ball.getHeight*scaleFactor);
If your image is "blurry", and you want the individual pixels to stay crisp, try loading the texture like that:
ball = new Texture("ball2.png");
ball.setFilter(TextureFilter.Nearest, TextureFilter.Nearest);
This prevents (default) linear interpolation when scaling the texture.

Color Libgdx Rectangle object

I'm making collisions for my game using libgdx and I'm having some issues. Things don't fall right. I'm using Rectangle objects around my character and terrain and would like to know if there is any way to color/show the rectangle so I can see exactly why are collisions are buggy. Is this possible?
These are the rectangles :
private Rectangle bottom, left, right, top, full;
full = new Rectangle(0f,0f,128f,10f);
bottom = new Rectangle(0f,0f,128f,16f);
left = new Rectangle(0f,16f,64f, 96f);
right = new Rectangle(64f,16f,64f,96f);
top = new Rectangle(0f,112f,128f,16);

You will need to use ShapeRenderer
https://libgdx.badlogicgames.com/nightlies/docs/api/com/badlogic/gdx/graphics/glutils/ShapeRenderer.html
ShapeRenderer shapeRenderer;
shapeRenderer = new ShapeRenderer();
shapeRenderer.begin(ShapeType.Line);
shapeRenderer.rect(x, y, width, height);
shapeRenderer.end();

Draw text in a Canvas and multiple lines

I'm starter with Canvas and Paint. I want to paint a text in a Canvas but it can be longer than the original Bitmap. So the text go out the Bitmap.
Is there some kind of automatic manager for this making a new line when the end is reached? or should I play with heights and distances? Thanks

yes, you can manage this with a StaticLayout or DynamicLayout

The best way is to draw text with StaticLayout:
// init StaticLayout for text
StaticLayout textLayout = new StaticLayout(
gText, paint, textWidth, Layout.Alignment.ALIGN_CENTER, 1.0f, 0.0f, false);
// get height of multiline text
int textHeight = textLayout.getHeight();
// get position of text's top left corner
float x = (bitmap.getWidth() - textWidth)/2;
float y = (bitmap.getHeight() - textHeight)/2;
// draw text to the Canvas center
canvas.save();
canvas.translate(x, y);
textLayout.draw(canvas);
canvas.restore();
See my blogpost for more details.

I would suggest that you also look at this code snippet found here:
https://stackoverflow.com/a/15092729/1759409
As it will manage the writing of your text within a certain width and height and automatically draws onto the canvas correctly.