glGetPolygonStipple returns to mask a 32×32 polygon stipple pattern. The pattern is packed into memory as if glReadPixels with both height and width of 32, type of GL_BITMAP, and format of GL_COLOR_INDEX were called, and the stipple pattern were stored in an internal 32×32 color index buffer. Unlike glReadPixels, however, pixel transfer operations (shift, offset, pixel map) are not applied to the returned stipple image.
GL_INVALID_OPERATION is generated if glGetPolygonStipple is executed between the execution of glBegin and the corresponding execution of glEnd.