Makes an animation of four circle growing and shrinking while changing color.

circles.jl

using Javis
using ColorSchemes

# Set the color scheme
# More options:
# https://juliagraphics.github.io/ColorSchemes.jl/stable/catalogue/
colors = ColorSchemes.cool

function circ(radius, color="white")
    sethue(color)  # Set the color of the circle
    setdash("solid")  # Set the edge style
    setline(8)  # Set the linewidth
    # Draw a circle with `radius` centered at the origin
    circle(O, radius, :stroke)
end

# Create a 500px × 500px video with 100 frames
video = Video(500, 500)
num_frames = 100

# Set the background for each frame
Background(1:num_frames, (args...) -> background("black"))

 # Radius of circle i in frame t
r(t, i) = 200sin(2π*t/num_frames) + 10i

# Color of circle i in frame t
c(t, i) = colors[min(t + 10(i-1), 100)]

# Draw four circles with radii that grow and shrink colors that change.
for i in 1:4
    Object(1:num_frames, (_, _, t) -> circ(r(t-i, i), c(t, i)))
end

# Render the video at 24 frames per second
render(video, pathname="circle.gif", framerate=24)