# convert an EAN-13 number to barcode
# Wolfgang.Urban@schule.at

import string

# part 1, even parity
A = ["0001101","0011001","0010011","0111101","0100011",
     "0110001","0101111","0111011","0110111","0001011"]

# part 1, odd parity (reversed and 0<->1)
B = ["0100111","0110011","0011011","0100001","0011101",
     "0111001","0000101","0010001","0001001","0010111"]

# part 2, (0<->1)
C = ["1110010","1100110","1101100","1000010","1011100",
     "1001110","1010000","1000100","1001000","1110100"]

# coding of part 1 depending on first digit (#13 from back) 
CODE13 = ["AAAAAA","AABABB","AABBAB","AABBBA","ABAABB",
          "ABBAAB","ABBBAA","ABABAB","ABABBA","ABBABA"]

SPACER = "01010"
DELIMITER = "101"

# find EAN checksum
def ean_checksum(n=401456178012):   # should give 3
    weight = 3
    check = 0
    while n != 0:
        n,r = divmod(n,10)
        check += r*weight
        weight = 4-weight           # 3,1,3,1,...
    check = (10-check%10)%10
    return check

# find ISBN checksum
def isbn_checksum(n=351902520):     # should give 5
    weight = 1
    check = 0
    while n != 0:
        n,r = divmod(n,10)
        check += r*weight
        weight += 1                 # 1,2,3,4...
    check = (10-check%10)%10
    return check
    

# build string of barcode bits
def ean(n=4014561780123):
    s = string.zfill(str(n),13)

    code = ""
    # build part 1
    coding13 = CODE13[int(s[0])]
    for x in range(6):
        cc = coding13[x]
        if cc=="A": code += A[int(s[x+1])]
        else: code += B[int(s[x+1])]
    code += SPACER
    # append part 2
    for x in s[7:13]:
        code += C[int(x)]

    return DELIMITER+code+DELIMITER


from Tkinter import *


# plot EAN code using small bars (1 pixel width)
def show_ean(n=9012345003154):
    root = Tk()
    root.title("EAN-13")
    cv = Canvas(root,width=105,height=60)
    cv.pack()

    c = ean(n)
    for i in range(len(c)):
        b = 45
        if i in (0,1,2,94,93,92,46,47,48,49): b += 5
        if c[i]=="1": cv.create_line(5+i,5,5+i,b)


# double size bars including number
def show_ean2(n=9012345003154):
    root = Tk()
    root.title("EAN-13")
    cv = Canvas(root,width=215,height=120)
    cv.pack()

    c = ean(n)
    for i in range(len(c)):
        b = 90
        if i in (0,1,2,94,93,92,46,47,48,49): b += 14
        if c[i]=="1":
            cv.create_line((5+i)*2+7,10,(5+i)*2+7,b)
            cv.create_line((5+i)*2+7+1,10,(5+i)*2+7+1,b)

    s = string.zfill(str(n),13)
    cv.create_text(8,104,text=s[0],font=("Courier",13))
    cv.create_text(66,104,text=s[1:7],font=("Courier",13))
    cv.create_text(158,104,text=s[7:13],font=("Courier",13))