Spinner Icon Generation Script

A potential employer asked me to code up a quick Android application as a challenge. I enjoyed doing it, but in the course of building it I discovered, surprisingly, that “image loading” spinner art was not just a simple web search away – or, at least, I wasn’t able to find any easily. Sure, I could pay for one – but why would I do that? Instead, I quickly cranked out something by hand, so I could submit the application. However, I thought to myself that as soon as I had a moment, I should write a quick script to generate a pretty spinner (prettier than I did by hand, that’s for sure.) Here’s the script:

#! /usr/bin/python

import math
from PIL import Image

def makeSpinner(filename, size, thickness):
    """Make a spinner image. A square image of size x size will be allocated.
    The spinner will be contained in a ring with an outer diameter of size
    and an inner diameter of size-thickness."""

    image = Image.new('RGBA', (size,size), 0)
    center = int(size / 2.0)
    radius = int(size / 2.0)

    angle = 0.0
    anglestep = math.atan(0.5 / radius) * (180.0 / math.pi)
    while angle < 360.0:
        bright = int(255 * (1.0 - angle/360.0))
        color = (bright, bright, bright, 255)
        angle_radians = math.pi * angle/180.0
        for r in range(radius-thickness, radius):
            x = round(center + r * math.cos(angle_radians))
            y = round(center - r * math.sin(angle_radians))
            coordinate = (int(x), int(y))
            #print coordinate, color
            image.putpixel(coordinate, color)
        angle += anglestep

    image.save(filename + '.png', 'PNG')

# Make the spinners for the application.
makeSpinner('ic_progress', 128, 16)
makeSpinner('ic_progress_small', 64, 8)

And here are the outputs of this script. I think they look pretty nice (although the one part that doesn’t show well here is the transparency):




This is just another example of how, right out of the box, with all its libraries, Python is a fantastic and versatile tool. I particularly like the ability to so easily generate and manipulate images! The whole project, including the script shown above, can be found here, on my github page.


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