MagPi31-single

MAKE GAMES WITH PYTHON
Tutorial
pygame.draw.line(window,(255,255,255),(50,50),(75,75),1)
pygame.draw.line(window,(255,255,255),(75,75),(25,75),1)
pygame.draw.line(window,(255,255,255),(25,75),(50,50),1)
pygame.draw.line(window,(255,255,255),True,((50,50),(75,7
(500,400))
0,100,50,50))
0,150,50,50))
0,200,50,50))
50, 50
pygame.draw.line(window,(255,255,255),(75,75),(25,75),1) There! We have a friendly,
pygame.draw.line(window,(255,255,255),(25,75),(50,50),1)
white triangle with a 1px
edge. But when we look
Right You
50, 50
at that code, it looks like
can make 25, 75 75, 75
a triangle
a lot, doesn’t it? So many
from three
things, like the colour
separate
lines
or the width, are being
25, 75 75, 75
written again and again
just for the sake of it.
Each path is made of joined-together lines, but
pygame.draw.circle(window,(255,255,0),(250,200),20,1)
before we start joining things up, let’s draw a couple
There must be a better
way, and indeed there is!
pygame.draw.circle(window,(255,255,0),(250,200),20,1)
of standalone lines to familiarise ourselves with All we need is
them. We can do this with pygame.draw.line(). Edit
paths.py so your while loop is like the following:
pygame.draw.lines().
While pygame.draw.
line() lets us draw a line
250,200 between two points, pygame.draw.lines() enables us Above This
while True: 250,200
20px
to draw a sequence of lines between numerous points.
Each XY-coordinate point will be joined up to the next
20px
pygame.draw.line(window, (255,255,255), XY-coordinate point, which will be joined up to the next
(0, 0), (500, 400), 1) XY-coordinate point, and so on.
After running the code you’ll see that it’s exactly the
pygame.display.update()
same, except we did it in one line of code instead of
three. You might have noticed that we didn’t actually
close the triangle – Pygame did it for us. Just before we
If you run this code now, you’ll see a 1-pixel-wide
white line going from the top left to the bottom right
of our Pygame window. The parameters we pass to
pygame.draw.line start off the same way rectangles
and ellipses do. We first tell Pygame where we want to
draw the shape and then we choose a colour. Now things
change a little. The next argument is a tuple of the X and
pass the points for our shape to be drawn from, we can
pass either a True of a False value that will let Pygame
know that we want it to close our shapes for us. Change
it to False and we get the first two lines of our shape,
but not the third.
What if we want a more complex shape? We simply
add more points like so:
Y coordinates for where we want our line to start, and the
third argument is a tuple with the X and Y coordinates for
where we want our line to end. These are the two points while True:
between which our line will be drawn. The final argument
is the width of the line that is being drawn in pixels.
With this, we can now create shapes by defining
points in our window. Let’s draw that triangle we
#pygame.draw.lines(WHERE TO DRAW,
COLOUR, CLOSE THE SHAPE FOR US?, THE POINTS
TO DRAW, LINE WIDTH)
talked about earlier:
pygame.draw.lines(window,(255,255,255),
True, ((50, 50), (75, 75), (63, 100), (38,
100), (25, 75)), 1)
while True:
pygame.draw.line(window, (255,255,255),
(50, 50), (75, 75), True)
pygame.draw.line(window, (255,255,255),
(75, 75), (25, 75), True)
pygame.draw.line(window, (255,255,255),
(25, 75), (50, 50), True)
pygame.display.update()
pygame.draw.line(window,(255,255,255),(50,50),(75,75),1)
pygame.display.update()
pygame.draw.line(window,(255,255,255),True,((50,50),(75,75),(25,75)),1)
There you have it: a pentagon. If you want a hexagon or
even a triacontagon, just add more points. Give it a go.
So that’s how you draw shapes, lines and paths in
Pygame. Already we know enough to make programs
that could be used to display pixel art to our friends
and family.
triangle is made
up of one line with
multiple points.
Follow the colours
to see which
variable is which
NEXT
MONTH
In part two,
things will get
a little more
complicated
– we’ll be
animating all
of the shapes
we’ve learnt
to draw so
far. They’ll
bounce,
stretch and
spin, which
is where the
games begin…
raspberrypi.org/magpi March 2015 55