Performance comparison of image resizing methods in Pillow and PyVIPS

pillow-vs-vips.py

#!/usr/bin/env python


# Script for comparing Pillow vs PyVIPS used for this issue:
# https://github.com/libvips/pyvips/issues/148


import sys
import timeit
import pyvips
from pathlib import Path
from PIL import Image

OUT = Path(__file__).parent.joinpath('out')


image_path = sys.argv[1]
number, repeat = 10, 3

pyvips.cache_set_max_mem(0)


algorithms = dict(
    vips=dict(
        fast=lambda im, scale: im.shrink(scale, scale),
        adaptive=lambda im, scale: im.resize(1/scale, vscale=1/scale, gap=2.0, kernel='lanczos3'),
        slow=lambda im, scale: im.resize(1/scale, vscale=1/scale, gap=0, kernel='lanczos3'),
    ),
    pillow=dict(
        fast=lambda im, scale: im.reduce((scale, scale)),
        adaptive=lambda im, scale: im.resize(
            (round(im.width / scale), round(im.height / scale)),
            Image.LANCZOS,
            reducing_gap=2.0,
        ),
        slow=lambda im, scale: im.resize(
            (round(im.width / scale), round(im.height / scale)),
            Image.LANCZOS,
        ),
    )
)
finalize = dict(
    vips=lambda im: im.write_to_memory(),
    pillow=lambda im: im,
)
saving = dict(
    vips=lambda im, path: im.write_to_file(path, compression=1),
    pillow=lambda im, path: im.save(path, compress_level=1),
)
images = dict(
    vips=pyvips.Image.new_from_file(image_path),
    pillow=Image.open(image_path),
)


def get_time(app, method, scale):
    callback = algorithms[app][method]
    output_path = OUT.joinpath(f'{method}_{scale}x_{app}.png')
    image = images[app]
    try:
        saving[app](callback(image, scale), output_path)

        return min(timeit.repeat(
            lambda: finalize[app](callback(image, scale)),
            repeat=repeat,
            number=number
        )) * 1_000 / number
    except TypeError:
        pass


def print_comparison(header, times):
    best_time = min(times[k] for k in times if times[k] is not None)
    line = f'| {header} | '
    for label in times:
        if times[label] is not None:
            time = times[label]
            ratio = time * 100 / best_time
            line += f'{label} {time:6.2f}ms ({ratio:4.0f}%) | '
        else:
            line += f'{label}   {"-" * 4}ms {" " * 7} | '
    print(line)


for key in images:
    assert images['vips'].width == images[key].width
    assert images['vips'].height == images[key].height

print(f'\nSize: {images["vips"].width}x{images["vips"].height}\n\n')

print('-' * 69)
for scale in [8, 9.4, 16]:
    for method in algorithms['vips']:
        times = {app: get_time(app, method, scale) for app in algorithms}
        print_comparison(f'{scale:3}x {method:10}', times)
    print('-' * 69)

print('\n\n')
print('-' * 91)
for app in algorithms:
    for scale in [8, 9.4, 16]:
        times = {method: get_time(app, method, scale) for method in algorithms[app]}
        print_comparison(f'{app:6} {scale:3}x', times)
    print('-' * 91)