[Python] tk canvas telepromter text transparency problems

I have a fullscreen window with a fullscreen canvas. First I place a fullscreen background image in this canvas.

canvas = tk.Canvas(window, bg="white", bd=0)
canvas.pack(fill=tk.BOTH, expand=True)
canvas.update()

image = Image.open('bild.jpg')
newimage = image.resize((canvas.winfo_width(),canvas.winfo_height()),Image.LANCZOS)
photo = ImageTk.PhotoImage(newimage, master=canvas)
canvas.create_image(0, 0, anchor="nw", image=photo)
canvas.update()


Then I place a headline text on the top right and below this a longer text. The text is much longer than the screen height.

rectangle_width = int(canvas.winfo_width() * 0.45)
rectangle_x = canvas.winfo_width() - rectangle_width

headblock = canvas.create_text(
rectangle_x+10, 10,
anchor='nw',
text=headline,
font=('Helvetica', 18, 'bold'),
fill='black',
width=rectangle_width - 20
)
x1, y1, x2, y2 = canvas.bbox(headblock)
textblock = canvas.create_text(
rectangle_x+10, y2+10,
anchor='nw',
text=fulltext,
font=('Helvetica', 14, 'normal'),
fill='black',
width=rectangle_width - 20
)
canvas.update()


Now I wan't to animate the long text, like a telepromter, moving slowly upwards, so that viewers can read the full text. This works fine with canvas.move()

def animate():
canvas.move(textblock, 0, -1)
x1, y1, x2, y2 = canvas.bbox(textblock)
if y2 > canvas.winfo_height():
window.after(60, animate)


But while the textblock is moving up it is shown behind the headline. The problem is the background image. That should always be visible. If I place headline and text in different objects, labels, canvas, whatever, they are not transparent anymore.

Has anyone a good idea, how move the only the long text, while the image is always visible and the headline stays static?

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