How to enable GPU rendering in Python Gtk3 in Windows?

I noticed that Gtk in Windows seems to be rendering images using the CPU rather than the GPU (whereas in Linux this does not seem to be the case).

I am creating a program using Python, Gtk3, and OpenCV which streams video from a camera and displays it in a GtkImage. The program works but the moment I resize the image to a larger resolution, the framerate seems to drop. I notice that the CPU usage is higher, the larger the image is.

Here is a snippet of code:

import gi
gi.require_version("Gtk", "3.0")
from gi.repository import Gtk, GdkPixbuf, GLib

# This method is called in a thread that read() frames from cv2.VideoCapture and displays it into a GtkImage.
def writeDisplay(uiBuilder, frame):
    # Load frame from OpenCV into pixbuf
    frame = cv.cvtColor(frame, cv.COLOR_BGR2RGB)
    h, w, d = frame.shape
    pixbuf = GdkPixbuf.Pixbuf.new_from_data(
        frame.tostring(), GdkPixbuf.Colorspace.RGB, False, 8, w, h, w*d)

    # Load image into GtkImage
    imageDisplay = uiBuilder.get_object("display")
    GLib.idle_add(imageDisplay.set_from_pixbuf, pixbuf)
    pass

In Linux, I don't notice any frame drop which suggests that GtkImage is rendered by the GPU. However, in Windows it seems to be software rendered.

I should also note that I am using PyGObject in Windows using Msys2.

Is there any way of streaming video frames from OpenCV to a Gtk3 GUI using hardware acceleration?

GTK3 always uses the CPU to render, regardless of the platform. The only way to use the GPU to render something in GTK3 is through the GtkGLArea widget, where you have access to a GL context.