Black screenshot using Pyglet

Question

I've been trying to grab a screenshot of a window I created using the Pyglet module of Python. I used this line of code to grab the screenshot:

pyglet.image.get_buffer_manager().get_color_buffer().save('screenshot1.png')

Though there is no error occurring when I'm running the program and the screenshot file is created, the file is just black. Here is the complete code:

import pyglet
from pyglet import gl

window = pyglet.window.Window(500, 500)

@window.event
def on_draw():
    window.clear()
    pyglet.graphics.draw(2, pyglet.gl.GL_LINES, ('v2i', (200, 200, 400, 400)))


pyglet.image.get_buffer_manager().get_color_buffer().save('screenshot1.png')

pyglet.app.run()

Answer 1

You are taking a screenshot before the window had a chance to draw anything. Because the on_draw() event handler is only called after you start the the event handling loop with pyglet.app.run() .

One possible solution is to put the screenshot function into an event handler as well, for example:

@window.event
def on_key_press(symbol, modifiers):
    pyglet.image.get_buffer_manager().get_color_buffer().save('screenshot1.png')

This way, the screenshot is only taken after you press a key, which allows the window to draw its content first.