Screenshots are easy in libGDX!
No post-processing
The basic way of taking a screenshot is to call Pixmap.createFromFrameBuffer (formerly: ScreenUtils#getFrameBufferPixmap) and then write that pixmap to the disk:
Pixmap pixmap = Pixmap.createFromFrameBuffer(0, 0, Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
PixmapIO.writePNG(Gdx.files.external("mypixmap.png"), pixmap, Deflater.DEFAULT_COMPRESSION, true);
pixmap.dispose();
Post processing to guarantee clarity
However, if your screens have layered transparency, you need to postprocess the screenshot to remove any transparency. Otherwise the screenshots won’t look like what the user is expecting:
Pixmap pixmap = Pixmap.createFromFrameBuffer(0, 0, Gdx.graphics.getBackBufferWidth(), Gdx.graphics.getBackBufferHeight());
ByteBuffer pixels = pixmap.getPixels();
// This loop makes sure the whole screenshot is opaque and looks exactly like what the user is seeing
int size = Gdx.graphics.getBackBufferWidth() * Gdx.graphics.getBackBufferHeight() * 4;
for (int i = 3; i < size; i += 4) {
pixels.put(i, (byte) 255);
}
PixmapIO.writePNG(Gdx.files.external("mypixmap.png"), pixmap, Deflater.DEFAULT_COMPRESSION, true);
pixmap.dispose();
The GWT backend has some limitations in this regard, which require additional steps outlined here.