Slow blitting with combined pixel and surface alpha #1618

Test 0: 1000 blits of image size 1333, 1600
tested Blit no alpha: 68.406ms
tested Blit surface alpha: 464.457ms
tested Blit pixel alpha: 381.999ms
tested Blit pixel and surface alpha: 1925.622ms

Test 1: 1000 blits of image size 1333, 1600
tested Blit no alpha: 63.964ms
tested Blit surface alpha: 451.907ms
tested Blit pixel alpha: 380.308ms
tested Blit pixel and surface alpha: 1929.704ms

Test 2: 1000 blits of image size 1333, 1600
tested Blit no alpha: 64.182ms
tested Blit surface alpha: 457.898ms
tested Blit pixel alpha: 375.786ms
tested Blit pixel and surface alpha: 1927.906ms

import time
import pygame

filename = 'flyboy.png'

pygame.display.init()
screen = pygame.display.set_mode((720, 480))
ino_alpha = pygame.image.load(filename).convert()
isurf_alpha = pygame.image.load(filename).convert()
isurf_alpha.set_alpha(100)
ipixel_alpha = pygame.image.load(filename).convert_alpha()
idual_alpha = pygame.image.load(filename).convert_alpha()
idual_alpha.set_alpha(100)

def test(methods, tries = 1000):
	for method in methods:
		start = time.time()
		name = method(tries)
		results = (time.time() - start) * 1000
		print('tested {}: {}ms'.format(name, round(results, 3)))

def no_alpha(tries):
	for t in range(tries):
		screen.blit(ino_alpha, (10,10))
	return 'Blit no alpha'

def surf_alpha(tries):
	for t in range(tries):
		screen.blit(isurf_alpha, (10,10))
	return  'Blit surface alpha'

def pixel_alpha(tries):
	for t in range(tries):
		screen.blit(ipixel_alpha, (10,10))
	return  'Blit pixel alpha'

def dual_alpha(tries):
	for t in range(tries):
		screen.blit(idual_alpha, (10,10))
	return 'Blit pixel and surface alpha'

for i in range(3):
	tries = 1000
	w, h = ino_alpha.get_size()
	print(f'\nTest {i}: {tries} blits of image size {w}, {h}')

	test((no_alpha, surf_alpha, pixel_alpha, dual_alpha), tries)