Display sequence of images using matplotlib

Question

I have this simple python script using OpenCV to load images from a folder and display them in a loop. I want to reproduce this effect using matplotlib.

import cv2 as cv
import os

im_files = [for f in os.listdir('.') if f[-3:] == 'png']

for f in im_files:
    im = cv.imread(f, 0) #read image in greyscale
    cv.imshow('display', im)
    cv.waitKey(1)

cv.destroyAllWindows()

I tried the following script but the pyplot window which opens to display the plots becomes un responsive.

import pylab as pl
import os

files = [f for f in os.listdir('.') if f[-3:] == 'png']
pl.ion()
for f in files:
    im=pl.imread(f)
    pl.imshow(im)
    pl.draw()

I have googled a lot but couldn't find any solution. How do I go about doing this? I am using Anaconda 1.6 32bit on Windows 8.

possible duplicate of Why does my pylab animation slow down with each update? — tacaswell
– tacaswell, Commented Jul 26, 2013 at 20:19
@tcaswell, thanks for providing the links. This is what I was looking for. — Yash
– Yash, Commented Jul 26, 2013 at 20:50

tacaswell · Accepted Answer · 2013-07-26 20:17:35Z

27

img = None
for f in files:
    im=pl.imread(f)
    if img is None:
        img = pl.imshow(im)
    else:
        img.set_data(im)
    pl.pause(.1)
    pl.draw()

answered Jul 26, 2013 at 20:17

tacaswell

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masterfloda · Accepted Answer · 2018-03-16 04:17:38Z

8

I like the following way of doing this which is really straight-forward and allows the whole figure to be updated, including title, labels etc. rather than just the image.

import numpy as np
from matplotlib import pyplot as plt

for j in range(0,3):
    img = np.random.normal(size=(100,150))
    plt.figure(1); plt.clf()
    plt.imshow(img)
    plt.title('Number ' + str(j))
    plt.pause(3)

A random image is formed.

plt.figure creates the figure the first time round if it does not already exist, and thereafter just makes figure 1 the current figure.

plt.clf clears the figure so subsequent updates don't overlay each other. The image is then displayed with a title.

The plt.pause statement is the key, since this causes the display to be updated - including title, labels etc.

edited Mar 16, 2018 at 4:17

masterfloda

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answered Mar 15, 2018 at 22:58

robertofbaycot

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1 Comment

Sridhar Thiagarajan Over a year ago

plt.pause() is key

Bily · Accepted Answer · 2017-05-10 06:04:55Z

5

I have implemented a handy script based on matplotlib that just suits your need and much more. Check it here

In your case, the following snippet should work:

import os
from scipy.misc import imread

img_files = [for f in os.listdir('.') if f[-3:] == 'png']

# redraw_fn draw frame f in a image sequence
def redraw_fn(f, axes):
    img_file = img_files[f]
    img = imread(img_file)
    if not redraw_fn.initialized:
        redraw_fn.im = axes.imshow(img, animated=True)
        redraw_fn.initialized = True
    else:
        redraw_fn.im.set_array(img)
redraw_fn.initialized = False

videofig(len(img_files), redraw_fn, play_fps=30)

answered May 10, 2017 at 6:04

Bily

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