Creating Animated GIFs, programatically!

Note:
I’m using Ubuntu 16.04 to play.

Week 1: Making GIFs

It’s not my first attempt at creating moving images. Each time I met with a problem that stopped me in my tracks until I ran out of steam and lost interest. But now two changes brought me success!
First I found out that Pillow 3.4.0 can now save images sequences!

Second I discovered Gizeh, a very nice library written by Zulko. Gizeh is a wrapper for cairocffi, which is a Python binding for Cairo, which is a 2D graphics library written in C… Lots of things to learn!

I did get into some trouble while installing Gizeh. Pip installed a version that was different from what is available on github. I didn’t have access to some elements (ellipse, bezier_curve, more?). To fix this I just replaced the gizeh.py file on my computer with the one from github.

To help with the gif making process I made an image viewer using Pillow and Tkinter. Mixing those two also gave me trouble. For some reason ImageTk was missing and I had to install python-pil.imagetk (thanks to saulspatz). After I managed to get the viewer running it was trivial to make a GIF from my pictures. By the way, do you know about Lena Söderberg?

Once I learened to make GIFs the next step was to learn how to draw my own images. Being lazy I used Gizeh’s square example as a starting point. The idea was to have those squares revolve.

I learned a lot with this little project. Not only about code but also about animation. (Getting a gif to loop perfectly can be tricky)

ps. Don’t forget to read about beautiful Lena

Here’s the code:

import os

import gizeh as gz
import numpy as np

from PIL import Image


def rotating_squares(name):

    SIZE = 400 # dimension of the final picture

    fps = 30
    frames = 30 # how many frames in the GIF

    temp_name = 'frame_' # prefix for temporary png files

    temp_files = [] # our list of png files

    # We generate n_squares random values of size, angle, color, position.
    # 'rand' is a function that generates numbers between 0 and 1
    n_squares = 100
    sizes = 20 + 40 * np.random.rand(n_squares)
    angles = 2*np.pi * np.random.rand(n_squares)
    colors = np.random.rand(n_squares, 3)
    positions = SIZE * np.random.rand(n_squares, 2)


    # draw our frames and save temporary files as .png
    for frame in range(0,frames):

        surface = gz.Surface(SIZE, SIZE, bg_color=(0,0,0))

        for angle, size, pos, color in zip(angles, sizes, positions, colors):

            angle = (np.pi/frames) * frame / 2 + angle # rotate the square
            square = gz.square(size, xy=pos, angle=angle, fill=color,
                               stroke_width=size/20)
            square.draw(surface)

        frame_name = temp_name + str(frame) + '.png'
        temp_files.append(frame_name)
        surface.write_to_png(frame_name)


    # build the gif
    sequence = []
    for file in temp_files:
        sequence.append(Image.open(file)) # load png files as Pillow images

    sequence[0].save(name, save_all=True, append_images=sequence[1:],
               duration=1000/fps, loop=0)


    # clean up our temporary png files
    for file in temp_files:
        os.remove(file)



if __name__ == '__main__':
    rotating_squares('test.gif')

import os

import gizeh as gz

import numpy as np

from PIL import Image

def rotating_squares(name):

SIZE = 400 # dimension of the final picture

fps = 30

frames = 30 # how many frames in the GIF

temp_name = 'frame_' # prefix for temporary png files

temp_files = [] # our list of png files

# We generate n_squares random values of size, angle, color, position.

# 'rand' is a function that generates numbers between 0 and 1

n_squares = 100

sizes = 20 + 40 * np.random.rand(n_squares)

angles = 2*np.pi * np.random.rand(n_squares)

colors = np.random.rand(n_squares, 3)

positions = SIZE * np.random.rand(n_squares, 2)

# draw our frames and save temporary files as .png

for frame in range(0,frames):

surface = gz.Surface(SIZE, SIZE, bg_color=(0,0,0))

for angle, size, pos, color in zip(angles, sizes, positions, colors):

angle = (np.pi/frames) * frame / 2 + angle # rotate the square

square = gz.square(size, xy=pos, angle=angle, fill=color,

stroke_width=size/20)

square.draw(surface)

frame_name = temp_name + str(frame) + '.png'

temp_files.append(frame_name)

surface.write_to_png(frame_name)

# build the gif

sequence = []

for file in temp_files:

sequence.append(Image.open(file)) # load png files as Pillow images

sequence[0].save(name, save_all=True, append_images=sequence[1:],

duration=1000/fps, loop=0)

# clean up our temporary png files

for file in temp_files:

os.remove(file)

if __name__ == '__main__':

rotating_squares('test.gif')

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