How to iterate pixels with python API?

[Scallact]

I was finally able to crack this problem. Here is some sample code:

Code:

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

# your standard imports, don't forget Gegl
import gi
gi.require_version('Gimp', '3.0')
from gi.repository import Gimp
gi.require_version('GimpUi', '3.0')
from gi.repository import GimpUi
gi.require_version('Gegl', '0.4')
from gi.repository import Gegl # << Gegl needed

# [...] other imports [...]

# needed for this example
import random

#
# [...] some code [...]
#

def randomColors(layer) :
    # example on how to iterate over pixels with Gegl and apply these in batches
    # this is much faster than drawing one by one with Gimp.Drawable.set_pixel()
    # important : the changed pixels can't be undone, it's better to draw them on a new layer
    
    thisBuffer = layer.get_buffer()
    startx = 100
    starty = 100
    sizex =   80 # region size, preferably not too big, iterate if necessary
    sizey =   80
    
    rectangleRegion = Gegl.Rectangle.new(startx, starty, sizex, sizey)
    
    bufferSize = sizex * sizey
    bufferData = []
    i = 0
    
    while i < bufferSize :
        
        # attribute some random values to rgb
        r = random.randint(0,255)
        g = random.randint(0,255)
        b =  random.randint(0,255)
        
        bufferData.extend([r, g, b])
        
        i += 1
        
    thisBuffer.set(rectangleRegion, "RGB u8", bufferData) # << this is where we write pixels!
    layer.update(startx, starty, sizex, sizey) # << necessary refresh