CODEWITHSUNDEEP
pythontkintercairo
susie_socks
susie_socks

Reputation: 63

Cairo with tkinter?

Is it possible to draw on a Cairo Surface and then display that as a tkinter.PhotoImage? Could somebody provide an example or at least a description of how one would do this?

Upvotes: 4

Views: 2415

Answers (2)

Chris
Chris

Reputation: 31

@zeronineseven's answer works, but I found I needed to further call the tobytes() function, otherwise a pointer is returned which Image.frombuffer cannot understand. Maybe this is because of some update in Cairo or PIL in the meantime?

Also, the base64 gif method could work with PNG instead on Tk8+ (Python 3.4+??), allowing for full colour map.

self._image_ref = ImageTk.PhotoImage(Image.frombuffer("RGBA", (w, h), self.surface.get_data().tobytes(), "raw", "BGRA", 0, 1))

Upvotes: 0

zeronineseven
zeronineseven

Reputation: 169

There are quite a few ways to achieve what you want and tkinter.PhotoImage is definitely not the best one, unless you really have to use it. The simplest one is to use ImageTK module from Pillow library:

from tkinter import Tk, Label
from PIL import Image, ImageTk
from cairo import ImageSurface, Context, FORMAT_ARGB32


class ExampleGui(Tk):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        w, h = 800, 600

        self.geometry("{}x{}".format(w, h))

        self.surface = ImageSurface(FORMAT_ARGB32, w, h)
        self.context = Context(self.surface)

        # Draw something
        self.context.scale(w, h)
        self.context.rectangle(0, 0, 1, 1)
        self.context.set_source_rgba(1, 0, 0, 0.8)
        self.context.fill()

        self._image_ref = ImageTk.PhotoImage(Image.frombuffer("RGBA", (w, h), self.surface.get_data(), "raw", "BGRA", 0, 1))

        self.label = Label(self, image=self._image_ref)
        self.label.pack(expand=True, fill="both")

        self.mainloop()


if __name__ == "__main__":
    ExampleGui()

Otherwise you can do it by converting cairo's surface to base64-encoded GIF image(either with the help of Pillow or manually, which is going to be a little bit time consuming) and passing the result as "data" arg to tkinter.PhotoImage constructor(untested!):

    from io import BytesIO 
    from PIL import Image
    from cairo import ImageSurface, Context, FORMAT_ARGB32


    w, h = 800, 600

    surface = ImageSurface(FORMAT_ARGB32, w, h)
    context = Context(surface)

    output = io.BytesIO()
    image = Image.frombuffer("RGBA", (w, h), self.surface.get_data(), "raw", "BGRA", 0, 1)
    image.save(output, format="gif")
    b64 = base64.b64encode(output.read())

Note: On big-endian machines "ARGB" mode should be used for the source data AFAIK.

Upvotes: 3

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