Develop Reference

LibGDX coordinates after resizing

I have an actor on the screen, with a DragListener to move him around the stage, and a ClickListener. After a click on it i want to draw a rectangle around him (using ShapeRenderer), the important thing is that the rectangle position is updating after moving the actor. Works good, until I resize the window (I'm using ExtendViewport). The rectangle is not at the correct position (I'm taking the coordinates using Actor's getX() and getY() methods). Tried the Viewport's toScreenCoordinates() method but still it is not correct. Any help with this problem would be very appreciated.

Are you forgetting to update the projection matrix of your ShapeRenderer after resize? Something like this:
viewport.update();
shapeRenderer.setProjectionMatrix(viewport.getCamera().combined);

Sprite Cropping LibDGX

I've been trying to draw an image of a block with an eye on the screen. I want to be able to animate more than one texture in the same way, so drawing the animations by hand is not an option. The problem is that when I move the eyelid sprite higher up than completely closed, part of the eyelid shows above the expected bounds like this. Obviously, this is a problem as it looks quite unnatural. I'd like to either have an alternative solution to this problem, or be able to crop the eyelid's Sprite object to fit behind the rest of the image. The final image consists of the eyeball, pupil (as I want to be able to animate this too), eyelid, main body and the outlines, drawn in that order. The render function looks like this:
public void render(float delta) {
float height = this.eyelid.getHeight();
float eyeHeight = height*0.7f;
this.eyelid.setY(this.eye.getY()+(eyeHeight*((100-this.lid)/100f)));
batch.begin();
this.eye.draw(batch);
this.pupil.draw(batch);
this.eyelid.draw(batch);
this.main.draw(batch);
this.shade.draw(batch);
batch.end();
}
this.lid is the % of how closed the eye is, and the image for the eyelid itself can be found here. How could I solve this problem, or how could I crop the sprite? I don't want to have to reload the texture as a sprite every frame.

I think what you're looking for is the ScissorStack class, which is documented on the libGDX wiki. You can use this object to clip around the eye's frame so that the top of the lid doesn't show.

Moving and rotating a Collision rectangle

I am writing a simple game, or so it seemed, that has a functionality of rotating a Rectangle as the mouse moves. This did not seem like a problem at first but it just became a problem. What the Rectangle should do is rotate around a point as the mouse moves around on the Panel.
If you look at the picture, when the mouse moves the Rectangle will rotate. I know you can use the rotate functionality with Graphics2D.
g2d.rotate(angle, centerx, centery);
This is not very help full because I can not get the coordinates of the moving rectangle. This rotates the full graphics! How will I be able to draw this Rectangle so that it does this. I don't have an idea as on how to start. Please help.

Some more code and context would be nice, but based on the current question: You could create a transformed shape. Particularly, Rectangle and Rectangle2D implement the Shape interface. And you can create an AffineTransform that represents the rotation that you are currently doing to your Graphics. So the relevant part of the code should roughly look like
Rectangle2D rectangle = ...
AffineTransform at = AffineTransform.getRotateInstance(
angle, centerx, centery);
Shape rotatedRectangle = at.createTransformedShape(rectangle);
g2d.draw(rotatedRectangle);
You mentioned "collision" in the title. If you intend to use this rectangle in some sort of collision detection, you should note that it is not directly possible to intersect two arbitrary Shape objects. Particulary, you can not intersect the Shape rotatedRectangle with another Shape otherRotatedRectangle, but only with a Rectangle otherRectangle. If this is an issue, you have several options, but this would rather fit into a dedicated question.

Java "zooming" Canvas?

I have a java.awt.canvas object and I draw stuff with the Graphics2D (which I get from the bufferStrategy) and I'd like to "zoom" in and out.
So if I zoom in (scaling it up by a factor of 1) such that a line I draw from (0,0) to (10,10) Would be in reality drawn from (0,0) to (20,20)
Is this possible, or do I have to implement this myself?

Take a look at Graphics2D: http://docs.oracle.com/javase/7/docs/api/java/awt/Graphics2D.html
You apply a suitable transformation to the graphics to achieve many transformations, rotate, scale (aka zoom) and translation. Simplest way to zoom would probably be
graphics2d.scale(2.0, 2.0); // draw everything twice the original size

Sprite Rotation around a point Andengine/Java

Does anyone know how can I get a sprite/bitmap to rotate by a certain angle where the point on one the sides will always remain in the same position.
I have a blue line in the image and I need one of the sides to remain in the same position at all times.
It would be great help if somebody could tell me how to do this.
Im trying to do this in Andengine/Java. So a solution in either would be most helpful.
Thanks
Regards,
Yaro

The AndEngine has a good method called setRotationCenter. :) By default rotation center set to center of sprite (half of width, half of height). You can easily change this point.

The AndEngine is quite limited with regard to rotation and positioning, I've faced a similar problem on my own, and the only way to solve it was overriding methods and extending classes.
I'd recommend you to implantation the a new method which will set the rotation axis, and override the setRotation() method, to use this axis, I guess you could figure out how to rotate the sprite on a different axis by changing its position which changing its rotation

I just find out a solution for rotate a sprite at any center point. First you create a virtual entity and attach your sprite into this entity (notice: position of sprite is relative with your entity), then you move rotation center of the sprite (default at center of image) to overlap the rotation center of the entity. Final, you set rotation for the entity instead of the sprite. Hope this helpful ^^