Use the camera plugin as pointed out already. The camera plugin can be used to directly capture or to select from your library on your mobile. To upload you need on the server a http POST service and on the mobile another cordova / phonegap plugin file transfer.
I made a controller with 2 buttons, one to capture/select images and one to upload.
The code is on this github
go into the camera folder where you can install the 2 plugins (see top README.md file) and run phonegap run YOURPLATFORM.