## Animating with Python

Published 2021/11/27 by Jordan Hay

I created an animation in Python. Each frame is generated with a Numpy array of pixel colours and is output to an AVI file with cv2.```
'''
Renders a sine wave animation with Python.
Author: Jordan Hay
Date: 26/11/2021
'''
# - Imports
import numpy as np
import cv2
import math
from jmath.approximation import differentiate
# - Main
if __name__ == "__main__":
# X/Y Dimensious to output to
X = 1920
Y = 1080
# Framerate
frames = 60
# Function to draw
# Sine wave with 50 pixel amplitude rounded to integer values
# Should be noted that it will draw "upside down" y-axis points downwards
func = lambda x: round(50 * math.sin(x*0.05) + 540)
# Centre of x axis
centre = X//2
# Function that computes how close to the centre of the x-axis something is
centreness = lambda x: 1 - abs(x - centre)/centre
# Starting data
data = np.zeros((Y, X, 3), np.uint8)
# CV2 AVI output
output = cv2.VideoWriter('project.avi', cv2.VideoWriter_fourcc(*'DIVX'), frames, (X, Y))
# Starting points
x, y = (0, 0)
while x < X:
# Sample point
y = func(x)
# Insert in drawing
data[y:y+3, round(x):round(x)+3] = (255, centreness(x) * 255, centreness(x) * 255) # YX BGR
output.write(data)
# Get tangent gradient
m = differentiate(func, x).value
# Move along inversely proportionally to gradient
# This should result in drawing speed proportional to line length
if m != 0:
x += 1/m
# Plus some extra movement here
x += 1
output.release()
```

The source code has been published on Github, and the animation on Youtube.