How to convert PyCairo surface to OpenCV numpy and back in Python 3

Question

I would like to convert OpenCV image to PyCairo, make some manipulations (drawing etc.) and convert it back to OpenCV. Do you know how to do it? Simple examples would be enough. Thank you.

Answer 1

As specified in PyCairo's test code, converting a cairo.ImageSurface object to numpy array:

import cairo
import numpy as np

w = 300
h = 300

surface = cairo.ImageSurface (cairo.FORMAT_ARGB32, w, h)
ctx = cairo.Context (surface)

# Draw out the triangle using absolute coordinates
ctx.move_to (w/2, h/3)
ctx.line_to (2*w/3, 2*h/3)
ctx.rel_line_to (-1*w/3, 0)
ctx.close_path()
ctx.set_source_rgb (0, 0, 0)  # black
ctx.set_line_width(15)
ctx.stroke()

buf = surface.get_data()
array = np.ndarray (shape=(w,h,4), dtype=np.uint8, buffer=buf)