Pygame Stuttering Object

I got a problem with a python programm, using pygame. I want to make a sun in a solar system spin (rotate). It works partially: the problem about some strange 'stuttering' of the s

Solution 1:

Put the code for loading the images outside the loop

Solution 2:

I have rewritten my answer based on your comments and after having glanced over the pygame docs

You really do only need to load your images once. What I am doing here is always rotating the originally loaded sun to a new surface, using the incrementing rotation. The rotation always wraps back to 0 degrees. As for the jitter, I am sure that related to an aliasing artifact and maybe even your centering math. But my goal was to address the biggest performance hit which was reading your sun image from disk every frame (30 times a second)

import pygame as pg
import pygame.locals as local
import sys

def main():
    pg.init()

    xres=800
    yres=600

    try:
        xres=int(sys.argv[1]) 
        yres=int(sys.argv[2]) 

    except IndexError:
        pass

    screen = pg.display.set_mode((xres,yres)) 
    pg.display.set_caption("future rpg prepreprepalphawhatever")

    pg.mouse.set_visible(1)
    pg.key.set_repeat(1,30)

    clock = pg.time.Clock()

    rotation_stat = 0.0

    planet01 = pg.image.load("earth.png")
    planet01.set_colorkey((251,0,250), local.RLEACCEL) #load planet01

    sun = pg.image.load("sun.png") #load sun
    bg = pg.image.load("bg.png") #load background

    sizedbg = pg.transform.smoothscale(bg, (xres, yres))

    planet_pos = (xres/5-planet01.get_width()/2,yres/2-planet01.get_height()/2)

    running = 1

    xres_cent, yres_cent = xres/2, yres/2

    while running:

        clock.tick(30)

        for event in pg.event.get():
            if event.type == local.QUIT:
                running = 0
            if event.type == local.KEYDOWN:
                if event.key == local.K_ESCAPE:
                    pg.event.post(pg.event.Event(local.QUIT))

        rotation_stat += 1
        if rotation_stat % 360 == 0:
            rotation_stat = 0.0

        screen.blit(sizedbg, (0,0))
        screen.blit(planet01, planet_pos)

        sun_rect = sun.get_rect()
        sun_rotated = pg.transform.rotate(sun, rotation_stat)

        center = sun_rotated.get_rect().center
        sun_pos = (xres_cent-center[0], yres_cent-center[1])
        screen.blit(sun_rotated, sun_pos)

        pg.display.flip()

    pg.quit()


if __name__ == "__main__":
    main()