Turtle Graphics - Extract Color from onscreenclick

问题

I am using Turtle Graphics in Python for a larger program. I am able to return the point that the user clicks on using turtle.onscreenclick

However, I would like to extract the RGB color of the point that the user clicks on. Can this even be done in turtle graphics and how can this be accomplished? Thank you!

import turtle

# Global variables specifying the point clicked

xclick = 0
yclick = 0

# Draw a rectangle that is red

height = float(50)
length = height *(1.9)
length = round(length,2)
turtle.begin_fill()
turtle.color("red")
turtle.down()
turtle.forward(length)
turtle.right(90) 
turtle.forward(height)
turtle.right(90)
turtle.forward(length)
turtle.right(90)
turtle.forward(height)
turtle.right(90)
turtle.end_fill()

# Gets the click 

def getcoordinates():
    turtle.onscreenclick(turtle.goto)
    turtle.onscreenclick(modifyglobalvariables) 

# Modifies the global variables    

def modifyglobalvariables(rawx,rawy):
    global xclick
    global yclick
    xclick = int(rawx//1)
    yclick = int(rawy//1)
    print(xclick)
    print(yclick)

getcoordinates()
turtle.done()

回答1:

turtle doesn't have function to get pixel color. It uses tkinter (and widget tkinter.Canvas - turtle.getcanvas()) to display everything but it doesn't have function to get pixel color too.

Canvas keeps all as objects and second answer for "Get pixel colors of tkinter canvas" shows how to get color of object in position (x,y). Maybe it will work for you.

EDIT: I made working example

canvas uses different coordinates - it needed to change y = -y

import turtle

# --- functions --- (lower_case_names)

def get_pixel_color(x, y):

    # canvas use different coordinates
    y = -y

    canvas = turtle.getcanvas()
    ids = canvas.find_overlapping(x, y, x, y)

    if ids: # if list is not empty
        index = ids[-1]
        color = canvas.itemcget(index, "fill")
        if color != '':
            return color.lower()

    return "white" # default color 

def modify_global_variables(rawx,rawy):
    global xclick
    global yclick

    xclick = int(rawx)
    yclick = int(rawy)

    print(get_pixel_color(xclick, yclick))


def draw_rect(x1, y1, width, height, color):
    y1 = -y1
    canvas = turtle.getcanvas()
    canvas.create_rectangle((x1, y1, x1+width, y1+height), fill=color, width=0)

# --- main ---

# Global variables specifying the point clicked

xclick = 0
yclick = 0

# Draw a rectangle that is red

height = 50.0 # now it is float
length = height * 1.9
length = round(length, 2)

turtle.down()
turtle.color("RED")

turtle.begin_fill()

for _ in range(2):
    turtle.forward(length)
    turtle.right(90) 
    turtle.forward(height)
    turtle.right(90)

turtle.end_fill()

# Use tkinter.Canvas to draw rectangle

draw_rect(100, 100, length, height, 'green')

# Gets the click & Modifies the global variables    

turtle.onscreenclick(modify_global_variables) 

turtle.done()

来源：https://stackoverflow.com/questions/47381824/turtle-graphics-extract-color-from-onscreenclick

标签

python

turtle-graphics