Pixelperfect Collision, hitmask/blank error

[Trolkar8]

I am trying to understand the way that pixelperfect collisions works, I have made a program using two circles(images) bouncing around in the pygame window. This is the script:

import pygame, importedfunctions, random
pygame.init()
clock = pygame.time.Clock()
screen = pygame.display.set_mode([640,480])
class BallClass(pygame.sprite.Sprite):
    def __init__(self, x,y):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.image.load("ball.png")
        self.rect = self.image.get_rect()
        self.rect.left = x
        self.rect.top = y
        self.speed = [6,6]
    def move(self):
        global ballgroup
        x = self.rect.left
        self.rect.left += self.speed[0]
        y = self.rect.top
        self.rect.top += self.speed[1]
        if self.rect.left < 0 or self.rect.right > screen.get_width():
            self.speed[0] *= -1
            self.rect.left = x
        if self.rect.top < 0 or self.rect.bottom > screen.get_height():
            self.rect.top = y
            self.speed[1] *= -1
        for i in ballgroup:
            z = importedfunctions.PixelPerfectCollision(self, i)
            if z == True:
                self.speed[0] *= -1
                self.speed[1] *= -1
                print "collide!"
            else: print z
ballgroup = pygame.sprite.Group()
ball1 = BallClass(20,20)
ballgroup.add(ball1)
ball2 = BallClass(200,20)
ballgroup.add(ball2)

def blitting():
    global ballgroup, screen
    screen.fill([0,0,0])
    for i in ballgroup:
        i.move()
    for i in ballgroup:
        screen.blit(i.image,i.rect)
stop = False
def while_loop():
    while stop == False:
        clock.tick(30)
        blitting()
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                sys.exit()
        pygame.display.flip()
while_loop()

it uses pygame and this script:

def PixelPerfectCollision(obj1, obj2):
    """
    If the function finds a collision, it will return True;
    if not, it will return False. If one of the objects is
    not the intended type, the function instead returns None.
    """
    try:
        #create attributes
        rect1, mask1, blank1 = obj1.rect, obj1.hitmask, obj1.blank
        rect2, mask2, blank2 = obj2.rect, obj2.hitmask, obj2.blank
        #initial examination
        if rect1.colliderect(rect2) is False:
            return False
    except AttributeError:
        return None
 
    #get the overlapping area
    clip = rect1.clip(rect2)
 
    #find where clip's top-left point is in both rectangles
    x1 = clip.left - rect1.left
    y1 = clip.top  - rect1.top
    x2 = clip.left - rect2.left
    y2 = clip.top  - rect2.top
 
    #cycle through clip's area of the hitmasks
    for x in range(clip.width):
        for y in range(clip.height):
            #returns True if neither pixel is blank
            if mask1[x1+x][y1+y] is not blank1 and \
               mask2[x2+x][y2+y] is not blank2:
                return True
 
    #if there was neither collision nor error
    return False

The problem is that it always returns "None"(whic h makes the balls running through eachothers), the only thing I have determinated is that it should be something with the obj.hitmask and the obj.blank
Hope you understand the problem:/

i would be very grateful to the one/ones who can help
please help

[jamesh1999]

Uh dude there isn't an obj.hitmask. If you read the entire page on this subject INCLUDING the code example at the bottom you will see that you have to defing it using the other functions they give you somewhere in the middle. Apart from that nothing looks wrong so you could just copy and paste the functions in as well as the other section of code.