How to run python scripts using gimpfu from command line?

I'm trying to use functions of gimp 2.8.22 to convert a pdf to jpeg and i want to do that with a python script using the gimpfu library from my windows cmd (i have installed python 3.6.1).

Right now, i't trying to do that with an example script:

#!/usr/bin/env python

# Hello World in GIMP Python

from gimpfu import *

def hello_world(initstr, font, size, color) :
    # First do a quick sanity check on the font
    if font == 'Comic Sans MS' :
        initstr = "Comic Sans? Are you sure?"

    # Make a new image. Size 10x10 for now -- we'll resize later.
    img = gimp.Image(1, 1, RGB)

    # Save the current foreground color:
    pdb.gimp_context_push()

    # Set the text color
    gimp.set_foreground(color)

    # Create a new text layer (-1 for the layer means create a new layer)
    layer = pdb.gimp_text_fontname(img, None, 0, 0, initstr, 10,
                                   True, size, PIXELS, font)

    # Resize the image to the size of the layer
    img.resize(layer.width, layer.height, 0, 0)

    # Background layer.
    # Can't add this first because we don't know the size of the text layer.
    background = gimp.Layer(img, "Background", layer.width, layer.height,
                            RGB_IMAGE, 100, NORMAL_MODE)
    background.fill(BACKGROUND_FILL)
    img.add_layer(background, 1)

    # Create a new image window
    gimp.Display(img)
    # Show the new image window
    gimp.displays_flush()

    # Restore the old foreground color:
    pdb.gimp_context_pop()

register(
    "python_fu_hello_world",
    "Hello world image",
    "Create a new image with your text string",
    "Akkana Peck",
    "Akkana Peck",
    "2010",
    "Hello world (Py)...",
    "",      # Create a new image, don't work on an existing one
    [
        (PF_STRING, "string", "Text string", 'Hello, world!'),
        (PF_FONT, "font", "Font face", "Sans"),
        (PF_SPINNER, "size", "Font size", 50, (1, 3000, 1)),
        (PF_COLOR, "color", "Text color", (1.0, 0.0, 0.0))
    ],
    [],
    hello_world, menu="<Image>/File/Create")

main()

I try to run the script from my cmd like this:

gimp-2.8 --no-interface --batch '(python_fu_hello_world RUN-NONINTERACTIVE "Hello" Arial 50 red)' -b '(gimp-quit 1)'

However, no matter what i do, i always geht the same error message:

(gimp-2.8:1020): LibGimpBase-WARNING **: gimp-2.8: gimp_wire_read(): error

edit: Ok, thanks. I left out the interface statement and I also tried out the most simple example to figure out whats wrong:

#!/usr/bin/env python

# Hello World in GIMP Python

from gimpfu import *

def hello_world():
 gimp.message("Hello, GIMP world!\n")

register(
 "hello_world",
 'A simple Python-Fu "Hello, World" plug-in',
 'When run this plug-in prints "Hello, GIMP world!" in a dialog box.',
 "Tony Podlaski",
 "Tony Podlaski 2017. MIT License",
 "2017",
 "Hello World",
 "",
 [],
 [],
 hello_world,
 menu="<Image>/Filters/HelloWorld",
)

main()

The script actually works when i run it from Gimp itself, but when i try to run it from my cmd, Gimp opens with another cmd saying: Error: ( : 1) eval: unbound variable: hello_world

Does someone know what i'm missing here?

from How to run python scripts using gimpfu from command line?