Merge pull request kivy#2329 from matham/screenshot

Import glReadPixels from the correct place. Fixes kivy#2032.

Author: inclement

kivy/core/window/window_pygame.py

@@ -243,7 +243,8 @@ def screenshot(self, *largs, **kwargs):
         if filename is None:
             return None
         if glReadPixels is None:
-            from kivy.core.gl import glReadPixels, GL_RGBA, GL_UNSIGNED_BYTE
+            from kivy.graphics.opengl import (glReadPixels, GL_RGBA,
+                                              GL_UNSIGNED_BYTE)
         width, height = self.system_size
         data = glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE)
         data = str(buffer(data))

kivy/core/window/window_sdl.py

@@ -99,7 +99,7 @@ def screenshot(self, *largs, **kwargs):
         filename = super(WindowPygame, self).screenshot(*largs, **kwargs)
         if filename is None:
             return None
-        from kivy.core.gl import glReadPixels, GL_RGB, GL_UNSIGNED_BYTE
+        from kivy.graphics.opengl import glReadPixels, GL_RGB, GL_UNSIGNED_BYTE
         width, height = self.size
         data = glReadPixels(0, 0, width, height, GL_RGB, GL_UNSIGNED_BYTE)
         data = str(buffer(data))