La rotation que je fait ne ce fait pas depuis le centre

 
#!/usr/bin/python
import pygame
from pygame.locals import *
import random
import time
pygame.init()
fenetre = pygame.display.set_mode((340, 620), RESIZABLE)
font =pygame.image.load("font.png").convert()
font =pygame.transform.scale(font,(340,620))
fenetre.blit(font,(0,0))
pygame.display.flip()

cd = [390, 3270]
td = [190, 1270, 290, 2270, 40, 4180, 50, 5180, 60, 6180]
dt = [10, 1180, 20, 2180, 490, 4270, 590, 5270, 590, 5270, 690, 6270]
uc = [30, 3180]
dd = [70, 790, 7180, 7270]











xpiece = 160
ypiece = 0
p = 0
while p == 0 :
 idbox = 0
 piece = random.randint(1, 7)
 xpiece = 160
 ypiece = 0
 if piece == 1 :
  font2 =pygame.image.load("l.png")
  font2 =pygame.transform.scale(font2,(40,60)).convert_alpha()
  font2 = pygame.transform.rotate(font2, 90)
  fenetre.blit(font2,(xpiece,ypiece))
  piece = 10
 elif piece == 2 :
  font2 =pygame.image.load("j.png")
  font2 =pygame.transform.scale(font2,(40,60)).convert_alpha()
  fenetre.blit(font2,(xpiece,ypiece))
  piece = 20
 elif piece == 3 :
  font2 =pygame.image.load("i.png")
  font2 =pygame.transform.scale(font2,(20,80)).convert_alpha()
  fenetre.blit(font2,(xpiece,ypiece))
  piece = 30
 elif piece == 4 :
  font2 =pygame.image.load("t.png")
  font2 =pygame.transform.scale(font2,(60,40)).convert_alpha()
  fenetre.blit(font2,(xpiece,ypiece))
  piece = 40
 elif piece == 5 :
  font2 =pygame.image.load("z.png")
  font2 =pygame.transform.scale(font2,(60,40)).convert_alpha()
  fenetre.blit(font2,(xpiece,ypiece))
  piece = 50
 elif piece == 6 :
  font2 =pygame.image.load("s.png")
  font2 =pygame.transform.scale(font2,(60,40)).convert_alpha()
  fenetre.blit(font2,(xpiece,ypiece))
  piece = 60
 elif piece == 7 :
  font2 =pygame.image.load("o.png")
  font2 =pygame.transform.scale(font2,(40,40)).convert_alpha()
  fenetre.blit(font2,(xpiece,ypiece))
  piece = 70
 pygame.display.flip()
 ypiece2 = 0
 
 
 while ypiece2 != 600:
  ypiece += 0
  if piece in cd:
   xpiece2 = xpiece + 80
   ypiece2 = ypiece + 20
  elif piece in td:
   xpiece2 = xpiece + 60
   ypiece2 = ypiece + 40
  elif piece in dt:
   xpiece2 = xpiece + 40
   ypiece2 = ypiece + 60
  elif piece in uc:
   xpiece2 = xpiece + 20
   ypiece2 = ypiece + 80
  elif piece in dd:
   xpiece2 = xpiece + 40
   ypiece2 = ypiece + 40
  time.sleep(0.01)
  for event in pygame.event.get() :
   print xpiece
   if event.type == KEYDOWN:
    if event.key == K_LEFT :
     if xpiece != 20:
      xpiece -= 10
    elif event.key == K_RIGHT :
     if xpiece2 != 320:
      xpiece += 10
    elif event.key == K_DOWN :
     if ypiece2 != 590:
      ypiece += 20
    elif event.key == K_r :
     font2 = pygame.transform.rotate(font2, 90)
     print 1
  fenetre.blit(font,(0,0))
    fenetre.blit(font2,(xpiece,ypiece))
    pygame.display.flip()
   
   
   
   
   
   
   
   
   
   
   
   
 time.sleep(1)