display_grid.py

# This is simple Python code for displaying a numpy array as pixels and updating it
# with reasonable speed.
#
# The code is by Nathaniel Virgo and is in the public domain - you can do what you
# want with it.
#
# I don't tend to use jupyter for this kind of thing, so it displays in a window.
#
# It gets about 60 fps with a 500x300 array on my machine, and about 40 fps for
# 1000x1000. OpenGL would most likely be much faster, but this is not unreasonable
# for Python.
#
# It works correctly on a retina display (in that the pixels are sharp and not
# blurred), but unfortunately it doesn't display at retina resolution.
#
# to use it, just insert your own code to update 'buf' inside the loop. buf is
# in RGBX format, meaning it's a w*h*4 array of uint8s, but the 4th value is not
# used, it's just padding. (This seemed to be very slightly faster than using RGB.)

import numpy as np
import tkinter as tk
from PIL import Image, ImageTk
from timeit import default_timer as timer

root = tk.Tk()

w = 500
h = 300

buf = np.zeros((w,h,4), dtype=np.uint8)
imgbuf = Image.frombuffer('RGBX', (w,h), buf, 'raw', 'RGBX', 0, 1)

img = ImageTk.PhotoImage(image=imgbuf)

canvas = tk.Canvas(root,width=w,height=h)
canvas.pack()
canvas_img = canvas.create_image(0,0, anchor="nw", image=img)

frames_displayed = 0

while True:

	# code to update the image buffer. (Here we only update one pixel, so we're
	# testing the rendering time, not the time taken to compute the next image)
	buf[np.random.randint(w),np.random.randint(h),:] = np.ones(4)*255

	imgbuf = Image.frombuffer('RGBX', (w,h), buf, 'raw', 'RGBX', 0, 1)
	img = ImageTk.PhotoImage(image=imgbuf)

	canvas.itemconfig(canvas_img, image=img)

	root.update_idletasks()
	root.update()

	if frames_displayed==0:
		init_time = timer()
	frames_displayed+=1
	if frames_displayed%100==0:
		print("average frame rate:", frames_displayed/(timer()-init_time), "fps")