Use omni.kit.hydra_texture to get camera content without viewport widget

Hi all,
I have some questions about the code snippet as below

hydra_texture_factory = acquire_hydra_texture_factory_interface()
hydra_texture = hydra_texture_factory.create_hydra_texture(
# step 1
resource = hydra_texture.get_drawable_resource() # type:omni.gpu_foundation_factory._gpu_foundation_factory.RpResource
render_capture = omni.renderer_capture.acquire_renderer_capture_interface()
# step 2
render_capture.capture_next_frame_rp_resource("camera.png", resource)

Q1: Can I convert RpResource to raw rgb data? How can do that?
Q2: step 1 has been done and a RpResource,and then renderer forward one frame(camera position changed).The camera.png content is forward one frame?
Q3: How can I make sure captured image correct? Because camera postion maybe changed