How to convert CameraInfo sensor msgs to Images?

edit

is there any function for converting CameraInfo sensor messages to images

CameraInfo msgs do not encode images, so this is impossible and no such function exists.

Edit:

my .bag file contains only CameraInfo msg type

So only those messages, no other messages?

but the video that's recorded from the camera has a special format in which it's stored into

But not in the bag then? That's at least what you write in the previous sentence.

Is there a way at least to access the message to view raw string format?

Messages are not always strings, especially not images, so I'm not sure what you are asking.

Edit2:

Video was recorded from the camera, but the .bag wasn't recorded using Image msg type. It's structured like this:

some header
     <Preface Index>    // preface frame index
     <Message Data> // first frame record
....
     <Message Data> // last frame record
<Index Data>    // index of all records in the previous chunk
<Connection>    // connection specs
<Chunk Info>    // additional chunk info

Is this the structure of the bag, or data from the camera?