How to calculate the distance from a pixel to the camera according to a depth map and point cloud?

Hi! With the zed depth viewer, I can obtain and save RGB photos, depth maps and point clouds of a scene.
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My question is, how to obtain the distance of a pixel according to these saved images?
The example on the official website is to run a ZED camera to obtain the distance information of a certain point in real time.

Can zed2 read the distance information of a certain depth image in the system?
Thanks for a lot!