cs177: programming in multimedia objects

Python Programming, 2/e 1

CS177:Programming in Multimedia Objects

Recitation Topic:Graphics Library


Objectives To be familiar with the various graphic objects

available in the graphics library. To understand the fundamental concepts of

computer graphics, especially the role of coordinate systems

To be able to write simple graphics programs using the graphics library.


Simple Graphics Programming This chapter uses the graphics.py

library supplied with the supplemental materials.

Two location choices for graphics.py In Python’s Lib directory with other

libraries In the same folder as your graphics

program


Simple Graphics Programming Since this is a library, we need to

import the graphics commands>>> import graphics

A graphics window is a place on the screen where the graphics will appear.>>> win = graphics.GraphWin()

This command creates a new window titled “Graphics Window.”


Simple Graphics Programming Windows can be closed/destroyed

by issuing the command>>> win.close()


Simple Graphics Programming It’s tedious to use the graphics.

notation to access the graphics library routines.

from graphics import *The “from” statement allows you to load specific functions from a library module. “*” will load all the functions, or you can list specific ones.


Simple Graphics Programming Doing the import this way

eliminates the need to preface graphics commands with graphics.>>> from graphics import *>>> win = GraphWin()


Simple Graphics Programming A graphics window is a collection of

points called pixels (picture elements). The default GraphWin is 200 pixels tall

by 200 pixels wide (40,000 pixels total). One way to get pictures into the window

is one pixel at a time, which would be tedious. The graphics routine has a number of predefined routines to draw geometric shapes.


Point The simplest object is the Point. Like

points in geometry, point locations are represented with a coordinate system (x, y), where x is the horizontal location of the point and y is the vertical location.

The origin (0,0) in a graphics window is the upper left corner.

X values increase from right to left, y values from top to bottom.

Lower right corner is (199, 199)


Point Example>>> p = Point(50, 60)

>>> p.getX()

50

>>> p.getY()

60

>>> win = GraphWin()

>>> p.draw(win)

>>> p2 = Point(140, 100)

>>> p2.draw(win)

Circles Given a 2-Dimensional plane,

what two things do you need to draw a circle?



Circles Like circles in geometry, circles in

graphics library are represented by the center of the circle which is a Point and the radius of the circle


Circle Example>>> center = Point(100, 100)


>>> cir = Circle(center, 40)

>>> cir.draw(win)


Rectangle Rectangles are the graphics object

in graphics module which take the two points as parameters

These two points are the two ends of the diagonals of the rectangle


Rectangle Example>>> p1 = Point(100, 100)

>>> p2 = Point(150,150)


>>> rect = Rectangle(p1,p2)

>>> rect.draw(win)

How can you draw a square? We have a problem here. There

is no method in graphics library to draw a square. Can you suggest a way?



Lines We can interpret lines as a series

of points connecting the origin point to the destination point in one direction in a single dimension.

Lines in graphics library are represented in the same way and Line() takes two points as parameters and draws a line between those two points.


Line Example>>> p1 = Point(100, 100)

>>> p2 = Point(150,150)


>>> line = Line(p1,p2)

>>> line.draw(win)


Ovals Ovals in graphics library are drawn

inside a rectangle specified by two points in the window.

Oval takes two points as its parameter and constructs an oval in the bounding box determined by those two points.


Oval Example>>> p1 = Point(50, 100)

>>> p2 = Point(150,150)


>>> oval = Oval(p1,p2)

>>> oval.draw(win)


Polygons Polygons are the figures that has a

closed path consisting of lines joining the given set of points

Polygon() takes variable number of points as arguments and creates a polygon joining those set of points

Eg. Polygon(point1, point2, point3, …)


Polygon Example>>> p1 = Point(50, 100)

>>> p2 = Point(100,150)

>>> p3 = Point(75, 50)


>>> polygon = Polygon(p1,p2)

>>> polygon.draw(win)

Generic methods supported by every Graphics object setFill(color) : Fills the interior of object with specified color setOutline(color): Sets the outline of object to the given

colot setWidth(pixels): Sets the width of the outline to specified

pixels. draw(graphWin): Draws the object to the given window undraw(): Undraws the graphics object from a graphics

window move(dx,dy): Moves the graphics object dx units in x

direction and dy units in y direction clone(): returns the duplicate of that graphics object. The

clones are always in undrawn state. You need to call draw() on those objects to draw them on window.


Getting it all togetherfrom graphics import *

def main(): win = GraphWin() drawFace(win) drawEyes(win) drawNose(win) drawLips(win) drawTeeth(win) def drawFace(win): centerOfFace = Point(100, 100) face = Circle(centerOfFace, 50) centerOfLeftEye = Point(80,75) face.draw(win) def drawEyes(win): centerOfLeftEye = Point(80,75) leftEye = Circle(centerOfLeftEye, 10) centerOfRightEye = Point(120,75) rightEye = Circle(centerOfRightEye, 10) leftEye.draw(win) rightEye.draw(win)


Getting it all together (Cont.)def drawNose(win): noseEdge1 = Point(100, 90) noseEdge2 = Point(90, 110) noseEdge3 = Point(110,110) nose = Polygon(noseEdge1, noseEdge2, noseEdge3) nose.draw(win)

def drawLips(win): lipsEdge1 = Point(80,125) lipsEdge2 = Point(120, 125) lips = Line(lipsEdge1, lipsEdge2) lips.draw(win)

def drawTeeth(win): toothPoint1 = Point(90,125) toothPoint2 = Point(95, 130) toothPoint3 = Point(110, 125) toothPoint4 = Point(115, 130) tooth1 = Rectangle(toothPoint1, toothPoint2) tooth2 = Rectangle (toothPoint3, toothPoint4) tooth1.draw(win) tooth2.draw(win)

main()


cs177: programming in multimedia objects

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