Can a python turtle assess a background pixel color/change in color of the turtle screen to stop at a line or border?

Question

What I want to do is very simple in principle (if at all possible with pyton turtle). I want to draw a square and make the turtle stay inside the square when it gets to the line without explicitly giving coordinates when to turn. Instead of

if t.xcor() >= 300 or t.xcor() <= -300:
    t.dx *= -1

write a program to assess the underlying pixel color and stop/turn at line...

import turtle

win = turtle.Screen()
win.setup(600,600)
win.tracer(0)

t = turtle.Turtle()
t.shape('circle')
t.pensize(10)
t.up()
t.fd(200)
t.down()
t.lt(90)
t.fd(200)
for i in range(3):
    t.lt(90)
    t.fd(400)

t.lt(90)
t.fd(200)
t.up()
t.goto(0,0)
t.color('red')
t.dx = 1
t.dy = 1

while True:
    win.update()
    t.goto(t.xcor()+t.dx, t.ycor()+t.dy)
    #### Stop/change direction/follow line when pixel.color.whatever = 'black'

score 1 · Answer 1 · answered Jan 05 '20 at 06:40

You can't do this from within turtle, but you can do it by dropping down to turtle's tkinter underpinnings. However, it's detecting colors of overlapping objects, not pixels, and it can be slow:

Turtle Graphics - Extract Color from onscreenclick

How to get the area of shape filled using turtle

And finally, avoiding pixel color detection altogether by using distance() instead:

Python Collision Detection with x and y coordinates for border

How do i make colour detection in turtle

Which I can demonstrate reworking your example code:

from turtle import Screen, Turtle
from random import randrange

TARGET_DIAMETER = 300
CURSOR_SIZE = 20

screen = Screen()
screen.setup(600, 600)
screen.tracer(False)

target = Turtle()
target.shape('circle')
target.color('yellow')
target.shapesize(TARGET_DIAMETER / CURSOR_SIZE)

turtle = Turtle()
turtle.shape('turtle')
turtle.color('red')
turtle.penup()
turtle.setheading(randrange(360))

def move():
    turtle.forward(2)

    if turtle.distance(target) > TARGET_DIAMETER/2 - CURSOR_SIZE/2:
        turtle.undo()
        turtle.setheading(randrange(360))

    screen.update()
    screen.ontimer(move)

move()

screen.mainloop()

Can a python turtle assess a background pixel color/change in color of the turtle screen to stop at a line or border?

1 Answers1