RGB pixel to depth map
I'm using an Asus Xtion Pro, and trying to find the depth value for an rgb pixel. Currently, my ROS node subscribes to the topics camera/rgb/image_raw and camera/depth/image. The frames of these topics are not identical, so how do I find the corresponding depth value for some rgb value?
Moreover, are there some openni2_launch topics for depth and rgb that are in the same frame? And are the depth values from camera/depth/image in meters or some other unit?