Graphics API for Students of Python: GASP

Introduction

This sheet describes briefly all the graphics things (i.e., drawing pictures) you can easily do with the gasp module for Python. (You can actually do lots of other complicated graphics things with Python, but they’re, errrm, complicated. We’ve made a bunch of useful things easy using the gasp module, and these are what this sheet describes.)

There’s an introduction to graphics in Sheet 3 (Pretty Pictures), so this sheet is more a reference than an introduction. Some of it is very terse; ask a teacher if it doesn’t make any sense. (If you are a teacher or you are studying this on your own and it still doesn’t make any sense, feel free to send an email to gasp-dev@googlegroups.com .)

Coordinates

(0, 0) is at the bottom left of the window. The window is 640 pixels by 480, by default. (You can make it a different size if you want to.) Coordinates are given in units of one pixel.

All functions that take coordinates take them as a tuple (x, y).

Circle((300, 200), 10)     # :) This is good
Circle(300, 200, 10)       # :( This is bad

Colors

To access the color module GASP has to offer. Call color.* where * is the color you wish to call. For example: ` color.BLACK ` This is the color black. Check out the gasp color refrence chart to see all of the availble color options.

The Essentials

from gasp import *

begin_graphics()

...                         # all of your code

end_graphics()

These are the essentials. ` from gasp import * ` imports the gasp module, begin_graphics() starts the graphics window, and end_graphics() quits the graphics window and ends the program. It’s dead simple, but also dead necessary.

Graphics Functions

begin_graphics()

begin_graphics(width=800, height=600, title="My Game", background=color.YELLOW)

This creates a graphics window with the dimensions 800x600, a title of My Game , and a background color of yellow. With no arguments you get a white 640x480 graphics window titled Gasp .

width
The width of the window in pixels.
height
The windows height in pixels.
title
A string that will be the title of the window.
background
It is the background of the graphics window. It can either be a color or an image

end_graphics()

endgraphics()

Ends a graphics window.

clear_screen()

clear_screen()

Clears everything off of the graphics window. It looks like a new graphcs window as if you just called begin_graphics().

remove_from_screen()

remove_from_screen(obj)

removes those objects from the screen

obj
A screen object of a list of screen_objects you would like to remove from the screen

Screen Objects

The objects that you will be displayed in your graphics window. You can manipulate these objects using the screen object methods

Plot

Plot(pos, color=color.black, size=1)

It puts a dot on the screen.

pos
The coordinate on the screen that you wish to plot.
color
The color you wish the dot to be.
size
An integer that determinse the size the of the dot

Line

Line(start, end, color=color.black)

Creates a line on the screen.

start
The starting coordinate of the line.
end
The coordinate at which the line will end.
color
The color of the line

Box

Box(center, width, height, filled=False, color=color.black, thickness=1)

This creates a Box on the screen

center
A coorinate where the center of your box will be.
width
The width in pixels of the box.
height
The height of the box in pixels.
filled
A boolean value that determines if your box will be filled
color
The color of your box.
thickness
The thickness in pixels of your box’s lines.

Polygon

Polygon(points, filled=False, color=color.black, thickness=1)

Creates a polygon on the screen

points
A list of coorinates that is each point on the polygon. The must be more than two items in the list
filled
A boolean value. If it is False the polygon will not be filled. Else, the polygon will not be filled
color
The color of the polygon’s lines
thickness
An integer that determines the thickness of the lines.

Circle

Circle(center, radius, filled=False, color=color.black, thickness=1)

Draws a circle, its center is a set of coordinates, and the radius is in pixels. It defaults to not being filled and the color black.

center
The circle’s center coordinate.
width
An integer that is the radius of the circle
filled
A boolean value that determines if your circle will be filled
color
The color of your circle.
thickness
The thickness in pixels of the circles lines.

Arc

Arc(center, radius, start_angle, end_angle, filled=False, color=color.black, thickness=1)

Creates an arc on the screen.

center
A coordinate that is the center of the arc.
radius
An integer that is the distance between the center and the outer edge of the arc.
start_angle
The start angle in degrees of the arc
end_angle
The end angle in degrees of your arc
filled
A boolean value that if True it fills the arc
color
The color the arc
thickness
The thickness in pixels of the arc

Oval

Oval(center, width, height, filled=False, color=color.black, thickness=1)

Puts an oval on the screen wherever you want.

center
The center coordinate of the Oval
width
The width in pixels of the oval
height
The height of the oval in pixels
filled
A boolean value determining if the oval will be filles or not.
color
The oval’s color
thickness
The thickness of the ovals lines

Image

Image(file_path, center, width=None, height=None):

Uploads an image onto the screen. If you only pass width and not a height it automatically scales the height to fit the width you passed it. It behaves likewise when you pass just a height.

file_path
The path to the image.
center
The center coordinates of the image
width
The width of the image in pixels. If width equals None then it defaults to the image file’s width
height
The height of the image in pixels. If no height is passed it defaults to the image file’s height

Screen Object Methods

The methods that manipulates screen objects

move_to()

move_to(obj, pos)

Move a screen object to a pos

obj
A screen object you wish to move.
pos
The coordinate on the screen that the object will move to

move_by()

move_by(obj, dx, dy)

Move a screen object relative to it’s position

obj
The screen object you wish to move
dx
How much the object will move in the ‘x’ direction. Positive or negative.
dy
How much the object will move in the ‘y’ direction. A pixel value.

rotate_to()

rotate_to(obj, angle)

Rotate an object to an angle

obj
The screen object that will be rotated
angle
The angle in degrees that the object will be rotated to

rotate_by()

rotate_by(obj, angle)

Rotate an object a certain degree.

obj
The screen object you wish to rotate
angle
The degree that the object will be rotate. Can be positive or negative.

Text

Text()

Text(text, pos, color=color.black, size=12)

Puts text on the screen

text
A string of the text that will be displayed
pos
The center coordinate of the text
color
The color of the text
size
The font size

Sound

All of the functions that manipulate sound.

Sound()

Sound(file_path)

Creates a sound object

file_path
The path of the sound file you wish to make the sound object out of

play_sound()

play_sound(obj, loop=False)

Plays a sound object

obj
A sound object
loop
If loop equals false in will play the file all the way through one time. If loop equals True it will repeat the file untill it is stopped

stop_sound()

stop_sound(obj, finish=False, fade=True)

It stops a sound object that was playing

obj
The sound object you wish to stop
finish
If True it will wait to stop the file untill it has finished. If False it will imedietly stop.
fade
If True it will fade out. If False it will stop the sound

Mouse

mouse_position()

mouse_position()

Returns the current mouse coordinate

mouse_buttons()

mouse_buttons()

returns a dictionary of the buttons state. There is a ‘left’, ‘middle’, and ‘right’ key.

Keyboard

keys_pressed()

keys_pressed()

returns a list of all of the keys pressed at that moment.

Gasp Tools

screen_shot

screen_shot(filename)

It saves a screenshot of the current graphics screen to a png file.

filename
The file path relative to the current directory that the image will be written to.