Python Programming, 2/e 1 CS177: Programming in Multimedia Objects Recitation Topic: Graphics Library
Jan 05, 2016
Python Programming, 2/e 1
CS177:Programming in Multimedia Objects
Recitation Topic:Graphics Library
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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.
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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
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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.”
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Simple Graphics Programming Windows can be closed/destroyed
by issuing the command>>> win.close()
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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.
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Simple Graphics Programming Doing the import this way
eliminates the need to preface graphics commands with graphics.>>> from graphics import *>>> win = GraphWin()
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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.
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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)
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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?
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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
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Circle Example>>> center = Point(100, 100)
>>> win = GraphWin()
>>> cir = Circle(center, 40)
>>> cir.draw(win)
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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
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Rectangle Example>>> p1 = Point(100, 100)
>>> p2 = Point(150,150)
>>> win = GraphWin()
>>> 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?
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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.
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Line Example>>> p1 = Point(100, 100)
>>> p2 = Point(150,150)
>>> win = GraphWin()
>>> line = Line(p1,p2)
>>> line.draw(win)
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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.
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Oval Example>>> p1 = Point(50, 100)
>>> p2 = Point(150,150)
>>> win = GraphWin()
>>> oval = Oval(p1,p2)
>>> oval.draw(win)
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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, …)
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Polygon Example>>> p1 = Point(50, 100)
>>> p2 = Point(100,150)
>>> p3 = Point(75, 50)
>>> win = GraphWin()
>>> 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.
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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)
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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()
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