How can I modify the colors of pixels in a Texture?

Question

I have a Texture loaded via the AssetManager:

AssetManager manager = new AssetManager(...);
manager.load(textureFilepath, Texture.class);
manager.finishLoading();
Texture texture = manager.get(textureFilepath, Texture.class);

and I want to modify some of the pixel colors at runtime. How can I do that?

Thanks

--- Update ---------

Here's a test app, attempting to alter the pixmap doesn't change the appearance of the texture though:

public class AppTest extends ApplicationAdapter {

    SpriteBatch batch;
    Texture texture;

    public void create() {
        batch = new SpriteBatch();
        texture = new Texture("foo.jpg");
    }

    public void render () {
        Gdx.gl.glClearColor(0, 0, 0, 1);
        Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);

        batch.begin();
        batch.draw(texture, 100, 100);
        batch.end();
    }

    private void test() {
        TextureData textureData = texture.getTextureData();
        textureData.prepare();
        Pixmap pixmap = textureData.consumePixmap();

        for (int y = 0; y < 200; y++) {
            for (int x = 0; x < 200; x++) {
                pixmap.drawPixel(x, y, 0xff0000ff);
            }
        }
    }

    public boolean touchUp (int screenX, int screenY, int pointer, int button) {
        test();
    }
}

Answer 1

Short:

pixmap.drawPixel(x, y, color);

So first you need to create a Pixmap from the texture data:

TextureData textureData = texture.getTextureData();
textureData.prepare();
Pixmap pixmap = textureData.consumePixmap();

If you want to change red into green you need a loop and get the rgb888 value since getPixel return that for you:

for (int y = 0; y < pixmap.getHeight(); y++) {
  for (int x = 0; x < pixmap.getWidth(); x++) {
      if (pixmap.getPixel(x, y) == Color.rgb888(Color.Red))
      {
        pixmap.drawPixel(x, y, Color.Green);
      }
  }
}

If you already know what to change there is no need to loop and just use pixmap.drawPixel().

When you are done with your Pixmap magic you can create a new Texture for it.

Texture pixmapTexture = new Texture(pixmap);