in conclusion:
All image files are placed into a virtual hard disk file inside.
Installed on the windows docker in fact, in essence, is the aid of technology and hyper-v windows linux platform to create a virtual machine, you execute all commands are actually executed in the virtual machine, so all pull in to the local image will virtual hard disks file directory virtual machine, this file is the virtual hard disk file (somewhat similar to the principle of vmware).
concrete,
1. Start menu, right click -> Control Panel -> Administrative Tools -> Hyper-V Manager -> Right virtual machine settings. Figure:
2. Visible virtual hard disk file in the C: \ ProgramData \ DockerDesktop \ vm-data \ DockerDesktop.vhdx
3. If you need to change the default path, select "Move", then be guided
It also can click on the menu bar: Operation -> Hyper-v settings to adjust the default storage location for the virtual hard disk file of all your virtual machines.
Reference links:
1. https://segmentfault.com/q/1010000006745913
2. https://blog.csdn.net/StemQ/article/details/53150939