Draws a line using either Bresenham’s line algorithm (-> https://en.wikipedia.org/wiki/Bresenham%27s_line_algorithm) which is fast as it uses only two colors, when alias = True, or Xiaolin Wu’s line algorithm (-> https://en.wikipedia.org/wiki/Xiaolin_Wu%27s_line_algorithm) which is slower as it uses opacity to improve line resolution, when alias = False. This script was made to be imported in my project_3d script via the descartes.py script.

from math import *
from kandinsky import *

def putPixel(x,y,opacity,col,bgcol):
  r,g,b=color(col)
  bgr,bgg,bgb=color(bgcol)
  r+=(bgr-r)*(1-opacity)
  g+=(bgg-g)*(1-opacity)
  b+=(bgb-b)*(1-opacity)
  set_pixel(x,y,(r,g,b))

def drawLine(x0,y0,x1,y1,col=(0,)*3,bgcol=(255,)*3,alias=False):
  if abs(y1-y0)<abs(x1-x0):
    if x1<x0:
      x0,x1=x1,x0
      y0,y1=y1,y0
    
    dx=x1-x0
    dy=y1-y0
    m=dy/dx if dx!=0 else 1
    
    if alias:
      putPixel(int(x0),int(y0),1.0,col,bgcol)
    else:
      overlap=1-((x0+0.5)-int(x0+0.5))
      distStart=y0-int(y0)
      putPixel(int(x0+0.5),int(y0),(1-distStart)*overlap,col,bgcol)
      putPixel(int(x0+0.5),int(y0)+1,distStart*overlap,col,bgcol)
    
    if alias:
      putPixel(int(x1),int(y1),1.0,col,bgcol)
    else:
      overlap=((x1-0.5)-int(x1-0.5))
      distEnd=y1-int(y1)
      putPixel(int(x1+0.5),int(y1),(1-distEnd)*overlap,col,bgcol)
      putPixel(int(x1+0.5),int(y1)+1,distEnd*overlap,col,bgcol)
    
    for i in range(int(dx)+1):
      x=x0+i
      y=y0+i*m
      ix,iy=int(x),int(y)
      if alias:
        putPixel(ix,iy,1,col,bgcol)
      else:
        dist=y-iy
        putPixel(ix,iy,1-dist,col,bgcol)
        putPixel(ix,iy+1,dist,col,bgcol)

  else:
    if y1<y0:
      x0,x1=x1,x0
      y0,y1=y1,y0
    
    dx=x1-x0
    dy=y1-y0
    m=dx/dy if dy!=0 else 1

    if alias:
      putPixel(int(x0),int(y0),1,col,bgcol)
    else:
      overlap=1-((y0+0.5)-int(y0+0.5))
      distStart=y0-int(y0)
      putPixel(int(x0+0.5),int(y0),(1-distStart)*overlap,col,bgcol)
      putPixel(int(x0+1.5),int(y0)+1,distStart*overlap,col,bgcol)

    if alias:
      putPixel(int(x1),int(y1),1.0,col,bgcol)
    else:
      overlap=((y1-0.5)-int(y1-0.5))
      distEnd=y1-int(y1)
      putPixel(int(x1),int(y1+0.5),(1-distEnd)*overlap,col,bgcol)
      putPixel(int(x1)+1,int(y1+0.5),distEnd*overlap,col,bgcol)

    for i in range(int(dy)+1):
      x=x0+i*m
      y=y0+i
      ix,iy=int(x),int(y)
      if alias:
        putPixel(ix,iy,1,col,bgcol)
      else:
        dist=x-ix
        putPixel(ix,iy,1-dist,col,bgcol)
        putPixel(ix+1,iy,dist,col,bgcol)