loadFromData

import os
import sqlite3
from contextlib import closing
from PySide2.QtCore import QByteArray, QBuffer, QIODevice, QFile
from PySide2.QtGui import QImage

import timeit

source = QImage('test.png')

# print(timeit.timeit(lambda: source.save('testaaa.png'), number=100))

image_format = 'PNG'

bits = QByteArray()
buffer = QBuffer(bits)
buffer.open(QIODevice.WriteOnly)
source.save(buffer, image_format)

print(len(bits.data()))

f = QFile('test111.png')
f.open(QIODevice.WriteOnly)
f.write(bits)
f.close()

db_file = 'test1.db'

if os.path.isfile(db_file):
    os.remove(db_file)

with closing(sqlite3.connect(db_file)) as conn:
    cursor = conn.cursor()
    cursor.execute('create table images (format text, bytes blob)')
    for i in range(100):
        cursor.execute('insert into images (format, bytes) values (?, ?)', [image_format, bits.data()])
    conn.commit()

with closing(sqlite3.connect(db_file)) as conn:
    cursor = conn.cursor()
    def load():
        for i, (format, blob) in enumerate(cursor.execute('select format, bytes from images')):
            image = QImage()
            image.loadFromData(QByteArray(blob), format)
            # print(len(image.bits()), image.format())
            image.save(f'test_out/test_out_{i}.png')
    print(timeit.timeit(load, number=10))
    # load()