Dragging a texture (without jump) - libgdx

Question

How can I drag a texture (image) without making it jump and centering itself on the mouse cursor (what I have below in my code)?
When I click on the texture, nothing should happen, and when I drag, the mouse cursor should stay in place (relative to the edges of the texture).
Example: https://s31.postimg.org/ojapwbj6j/Untitled_1.jpg
SpriteBatch batch;
Texture texture;
OrthographicCamera camera;
Vector3 spritePosition = new Vector3();
float offsetX, offsetY;
Vector3 input;
#Override
public void create () {
batch = new SpriteBatch();
texture = new Texture("badlogic.jpg");
camera = new OrthographicCamera();
camera.setToOrtho(false);
}
#Override
public void render () {
Gdx.gl.glClearColor(1, 0, 0, 1);
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
batch.begin();
batch.draw(texture, spritePosition.x, spritePosition.y);
batch.end();
if (Gdx.input.justTouched()){
int x1 = Gdx.input.getX();
int y1 = Gdx.input.getY();
input = new Vector3(x1, y1, 0);
camera.unproject(input);
offsetX = x1 - spritePosition.x;
offsetY = y1 - spritePosition.y;
}
if (Gdx.input.isTouched()) {
spritePosition.set(Gdx.input.getX() - offsetX, Gdx.input.getY() - offsetY, 0);
}
}

Answer 1

What you need to do is work out the offset of the mouse position relative to your image, and subtract that, rather than half the width / height as you're doing at the moment.
Here's some very rough pseudocode to show what I mean - You'll need to rewrite as Java...
if Gdx.input.justTouched {
get mouse position from Gdx.input
camera.unproject it into cameraX and cameraY
offsetX = cameraX - imageX
offsetY = cameraY - imageY
}
if Gdx.input.isTouched {
spritePisition.set(Gdx.input.getX() - offsetX, Gdx.input.getY - offsetY)
}

Answer 2

Why are you using camera.unproject?
Try this:
Override
public void render () {
Gdx.gl.glClearColor(1, 0, 0, 1);
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
batch.setProjectionMatrix(camera.combined);
batch.begin();
batch.draw(texture, spritePosition.x, spritePosition.y);
batch.end();
if (Gdx.input.isTouched()) {
spritePosition.set(Gdx.input.getX() - texture.getWidth() / 2, Gdx.input.getY() + texture.getHeight() / 2, 0);
}
}