cntrstnw.py

Created on August 13, 2023

974 Bytes

The following Python script compares a contrast of colored text (foreground) color against a background color. It is important to have good, high contrast. High contrast allows for easy readability and it’s easier on the eyes. This becomes more important when considering web page development to allow accessibility.

Sources

“How to calculate colour contrast” Accessibility Developer Guide (ADG*). An initiative of Access for all. Last Edited July 29, 2023. Accessed August 8, 2023. https://www.accessibility-developer-guide.com/knowledge/colours-and-contrast/how-to-calculate/

“Relative Luminance” Web Content Accessibility Guidelines (WCAG) 2.0. W3C, Inc. (World Wide Web Consortium, Inc.) Last Edited December 11, 2008. Accessed August 8, 2023. https://www.w3.org/TR/WCAG20/#relativeluminancedef

My math and calculator blog: edspi31415.blogspot.com

from math import *
from kandinsky import *
# 2023-08-13 EWS
# Contrast - Numworks Version

# Source:
# www.w3.org, "WCAG 2.0"
# ADG*, "How to calculate colour contrast"

# CODE:
# subs
def lumin(r,g,b):
  r=compare(r/255)
  g=compare(g/255)
  b=compare(b/255)
  return .2126*r+.7152*g+.0722*b
def compare(x):
  if x<=.03928:
    x=x/12.92
  else:
    x=((x+.055)/1.055)**2.4
  return x

# main
print("Color Contrast \n(0-255) \nBackground color:")
r1=int(input("red? "))
g1=int(input("green? "))
b1=int(input("blue? "))
print("Text color:")
r2=int(input("red? "))
g2=int(input("green? "))
b2=int(input("blue? "))

# calc
l1=lumin(r1,g1,b1)
l2=lumin(r2,g2,b2)
cntr=(max(l1,l2)+.05)/(min(l1,l2)+.05)

# draw
c1=color(r1,g1,b1)
c2=color(r2,g2,b2)
cb=color(0,0,0)
cw=color(255,255,255)
fill_rect(0,0,320,240,c1)
draw_string("Contrast test: Numworks",25,25,c2,c1)
draw_string("Contrast: "+str(cntr),25,50,cb,cw)
draw_string("Press OK to continue.",25,150,c2,c1)