Python | Ellipse (different polygons) in Kivy

• Last Updated : 21 Sep, 2021

Kivy is a platform independent GUI tool in Python. As it can be run on Android, IOS, linux and Windows, etc. It is basically used to develop the Android application, but it does not mean that it can not be used on Desktops applications.

Ellipse:

Ellipse is a vertex canvas instruction. It allows drawing of a regular polygon, or an arc based on them. In this article, we will see different polygons have different number of sides and also many vertices on circle.
As in Kivy, we can make polygons based on an ellipse. Note, the angles in Kivy, are different than those in math. In Kivy, the 0-degree point, corresponds to the 90 degree-point, in math.

Note:
These are the formulas for x and y. These math formulas assume the center is 0, 0. Thus, after calculations are done, there has to be a translation by x of a and y of b. The width is 2a, and height is 2b.

N segments = N vertices
1) angle[i]= i*360/n ; i=0 to n
2) x[i]=a cos(angle[i])
3) y[i]=b sin(angle[i])
4) In kivy 12’o clock is 0 degree and increases clockwise but in math 3’o clock is 0 degree increases counter clockwise.

Program to show how we can make different polygon in kivy by Ellipse.

main.py file:

Python3

 # Code to create different polygons using Ellipse # import kivy moduleimport kivy   # this restrict the kivy version i.e# below this kivy version you cannot# use the app or softwarekivy.require("1.9.1")   # base Class of your App inherits from the App class.# app:always refers to the instance of your applicationfrom kivy.app import App # The GridLayout arranges children in a matrix.# It takes the available space and# divides it into columns and rows,# then adds widgets to the resulting “cells”.from kivy.uix.gridlayout import GridLayout # creating the Layout classclass Ellipsekv(GridLayout):    pass # creating the App class   class EllipseApp(App):    def build(self):        return Ellipsekv() # run the Appif __name__=='__main__':    EllipseApp().run()

Ellipse.kv file

Python3

 # Ellipse.kv file of the code ################################################### # For the arcs, we have to give the start,# and the end angle. We use default number of segments,# 180, and 5, for the two ellipse arcs.# The rest of the kv file, corresponds, to the other,# 6 ellipse arcs, following the same pattern. #:set angle_start_row2 240#:set angle_end_row2 480#:set angle_start_row3 120#:set angle_end_row3 240 #################################################  :     # Setting column to 4    cols:4 ################################################## # Row 1         # Creating Canvas    canvas:        Color:            rgb: 0, 0, 1        Rectangle:            pos: self.pos            size: self.size     # This will create the circle    # as no segment is fixed in Ellipse    # so by default it creates the circle    RelativeLayout:        canvas:            Color:                rgb: 1, .8, .5            Ellipse:                pos: 0, 0                size: self.size     # This will create pentagon as    # segment = 5    RelativeLayout:        canvas:            Ellipse:                segments: 5                pos: 0, 0                size: self.size     # This will create square shape as    # segment = 4    RelativeLayout:        canvas:            Ellipse:                segments: 4                pos: 0, 0                size: self.size     # This will create triangle as    # segment = 3    RelativeLayout:        canvas:            Ellipse:                segments: 3                pos: 0, 0                size: self.size                 ################################################# # Row 2     RelativeLayout:        canvas:            # Assigning colour to all in row 2            Color:                rgb: 1, .59, .86             # Creating the arc as assigned above              Ellipse:                angle_start: angle_start_row2                angle_end: angle_end_row2                pos: 0, 0                size: self.size      # Creating the arc as assigned above    # segment 5    RelativeLayout:        canvas:            Ellipse:                angle_start: angle_start_row2                angle_end: angle_end_row2                segments: 5                pos: 0, 0                size: self.size     # Creating the arc as assigned above    # segment 4    RelativeLayout:        canvas:            Ellipse:                angle_start: angle_start_row2                angle_end: angle_end_row2                segments: 4                pos: 0, 0                size: self.size     # Creating the arc as assigned above    # segment 5    RelativeLayout:        canvas:            Ellipse:                angle_start: angle_start_row2                angle_end: angle_end_row2                segments: 3                pos: 0, 0                size: self.size ################################################# # Row 3     RelativeLayout:        canvas:            Color:                rgb: .5, .5, .5            Ellipse:                angle_start: angle_start_row3                angle_end: angle_end_row3                pos: 0, 0                size: self.size     RelativeLayout:        canvas:            Ellipse:                angle_start: angle_start_row3                angle_end: angle_end_row3                segments: 5                pos: 0, 0                size: self.size     RelativeLayout:        canvas:            Ellipse:                angle_start: angle_start_row3                angle_end: angle_end_row3                segments: 4                pos: 0, 0                size: self.size     RelativeLayout:        canvas:            Ellipse:                angle_start: angle_start_row3                angle_end: angle_end_row3                segments: 3                pos: 0, 0                size: self.size

Output: This is the result. We have 3 rows and 4 columns. Rows 2 and 3 are arc shapes, while Row1 has the default angles, 0 and 360 to form a complete circle. By changing the size of the window manually, we can get ovals, and shapes based on them. For the arc, the number of segments, corresponds to the number of lines that approximate the circular portion.

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