image-dired-cmd-create-thumbnail-program

image-dired-cmd-create-thumbnail-program is a variable defined in `image-dired.el'.
Its value is

"convert"

• This variable may be risky if used as a file-local variable.

Documentation:
Executable used to create thumbnail.
Used together with `image-dired-cmd-create-thumbnail-options'.

You can customize this variable.