Testing for image collision Pygame

Question

I'm making a basic car game, and would like the car to move faster on the track and slower on the grass. I have two separate images to create the background, one is the track, and the other is the rest of the image.

I have a car sprite that can move around the screen, but when testing for collision I don't know what to do. I tried:

track = track = SCREEN.blit(track, (0, 0))

if track.colliderect(car):
    speed += 1.5
else:
    speed += 0.5

But I'm told this only works for rect objects, what do I need to do?

I've not been able to find anything related to image collision, that would help my situation, so if there are any other questions answering this please tell me.

I assume the rest of the track is see-through? If your car is much thinner than the track you can simply check if any corner of the rect of your car is on the track by checking the color of the track at that position. (or if you want to speed up only if you are completely on track, all corners) — JeD
Yes the rest of the track is see through, how would I go about checking if the corners are on it? — George Willcox

JeD JeD · Accepted Answer · 2016-03-01T19:42:21

Basically like this:

def isOnTrack(track,car):
    #one corner; a is alpha, the transparency
    #If a is 0 that means completely transparent
    if track.get_at(car.x,car.y).a==0:
        return false

    #do this for all four corners of car

    return true

The Image you use for this collision has to ONLY containt the track

track.get_at(x,y) returns a color value if track is a surface

Color has 4 fields, r g b a

I check a; the transparency

Testing for image collision Pygame

1 Answers