Step-by-step codes: read / encode PDF417

Do you like codes? Well, or do not love. In any case, sometimes you need to know how to use them correctly. You can go the long way, as I did last time , but when there is no time, it is easier to use the instructions.

So, let's deal with everything you need to read and / or write PDF417. After all, it’s not always at hand to find a smartphone with a program for reading them. And for the record - and even more so.

Attention, under the cut - 9 images with a total size of 2.79 MB, 6 tables and a few formulas.

Table of contents

01. History of PDF417 and right of use

( Back | Table of Contents | Forward )

PDF417 invented by Symbol Technologies Inc. in 1991, and on September 7, 1993, a US patent was issued for him under the number 5,243,655 (available, for example, here ). In fact, the patent describes not just a coding method, but a complex system for encoding and decoding data ( "System for encoding and decoding data in machine readable graphic form" ). In addition, not all of the recommendations in the patent are currently used.

, PDF417 , .

: ISO/IEC 15438:2015, PDF417, — 198 CHF ( ). , . , , .

02.

( | | )

() PDF417 (. 1) — , . , ( ) . ().

, . PDF417 3 90 , 3 30 .

. 1. PDF417

17 ( ), 4 4 . 1 6 .

$$$x-$($$$x_0, …, x_7$). 3 (), "", "". , $$$t-$, $$$t_i = x_{i-1} + x_i$. .

PDF417 . , $$$0, 3, 6,…$, — $$$1, 4, 7,…$, — $$$2, 5, 8,…$. (. 2), .

$$$x-$$$$t-$:

$$$C = (x_0 - x_2 + x_4 - x_6) mod 9$,
$$$C = (t_1 - t_2 + t_5 - t_6) mod 9$,

$$$mod 9$— 9.

, 3 , 9 , . : $$$C = (n_r mod 3) * 3$.

PDF417 929 ( 000 928).

03.

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(. 2):

• , , ($$$N$);
• $$$N-1$, ;
• $$$N_e$;
• $$$N_r$.

. 2. PDF417

, , ( 900, ), $$$d_0, d_1,…$.

04.

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, PDF417 000 928 . , 2 787 .

000 899 .

900 : 928 — (. 1). 900, 901, 902, 913 924, .

. 1. PDF417. ,

PDF macro PDF417 . , ( ) .

ECI / GLI — Extended Channel Interpretation / Global Label Identifier — , . , ( , GLI 0, ), .

04.a) (TC, Text Compaction Mode)

( | | )

PDF417 ( ). 4 :

• Alpha ( );
• Lower case;
• Mixed;
• Punctuation.

. 2. GLI 0

• al, ll, ml pl — alpha, lower case, mixed punctuation (l = latch);
• as ps — alpha punctuation (s = shift) .

900 2 :

$$$V = 30 * H + L$,

$$$V$— 900, $$$H$— , $$$L$— . $$$X_1$$$$X_2$.

, , $$$H$-, $$$L$- 29.

shift- . latch- .

04.b) - (BC, Byte Compaction Mode)

( | | )

900. 256. :

• 901 ( 6);
• 924 ( ).

, 6 5 256 900. , 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, (. 3).

. 3. , -

:

924, 001, 620, 089, 074, 846.

6, 6 5 , — . , 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09 :

901, 001, 620, 089, 074, 846, 007, 008, 009.

, - 913.

04.c) (NC, Numeric Compaction Mode)

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10 900. , 0 9. , 44 15 .

902. , 13 . , 3 ( , 2.93) , , (2 ).

900 1 , . 4. , 1 .

. 4. ,

05.

( | | )

. PDF417 2 . , , (. 3).

. 3. PDF417

:

• , (erasures), " ";
• , , (errors), " ".

:

$$$e -$;
$$$k -$;
$$$s -$;
$$$N_e = 2^{s+1} -$.

:

$$$e + 2k \leq d - 2$

2 , , , .

Error Correction Capacity, , . , , . , $$$s = 0$, , :

$$$e + 2k \leq d - 3$.

2 , . 2 .

, $$$s = 3$, 13 , 7 , , (9 2 ..).

- $$$GF(929)$. .

(. 4).

. 4.

06.

( | | )

( 03), PDF417.

, , . , , , , , (. 5).

. 5.

07.

( | | )

x-, 17- GitHub

( 02), PDF417 3 (0, 3 6) 929 . 17- , x-. , , , , . 5.

. 5. 20 x-

08. 8-

( | | )

GLI 0

ASCII 0:127. 128:255 PC 437.

. 6. GLI 0, PDF417

GLI 1

ISO 8859-1 ().

09. PDF417,

( | | )

PDF417 .

, , PDF417 - -, x- 81111113 711311121 (18 ) .

, PDF417 (. 6). , - -.

. 6. 0 PDF417

10.

( | | )

. ( 0, 0). , 19 (. 7). , , ( , , 06). , 1 -, 18 - 8 , 27, .

. , .

. 7. ,

11. PDF417

( | | )

, 000 928 (. 8). , , .

. 8.

— 900 : 928. . 8, . , (TC, 04.a).

12.

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, , 2 :

$$$V = 30 * H + L$

$$$H$30, $$$L$— 30.

:

(27)(07) (19)(19) (15)(18) (28)(14) (19)(19) (28)(07) (27)(00) (01)(17) (29)(17) (02)(14) (12)(29) (19)(15) (14)(18) (19)(28) (19)(05) (00)(00) (09)(06) (02)(29)

( . 2):

(ll)https(ml)://(al)H(ll)abr(ps).com(ps)/post(ml)/500962(ps)

(ll), (ml), (al) (ps) 04.a.

:

https://Habr.com/post/500962

, . 8 ( 05).

13.

( | | )

— . .

, . , 3 . , ( ).

, — $$$x-$, $$$t-$( 02). PDF417 , ( ..), , , — . , .

. , , ( ). .

14.

( | | )

, , .

1.  P -   
2. ,      (900)
3.  N -  ,   ,    P

    4.  N ≥ 13
        5.     (902)
        6.    
        7.  P
        8.    3

    9.  N < 13
        10.  T -    ,  
             .      
              (901, 902, 913, 924)    
              13 .

        11.  T ≥ 5
            12.     (900)
            13.  
            14.  P
            15.   3

        16. T < 5
            17.  B -    , 
                  P.     11
                 4.

            18. B == 1 &   - 
                19.      1  (913)
                20.   
                21.  P
                22.    3

            23. 
                24.     (901  924   
                     ,  04.b)
                25. 
                26.  P
                27.    3

15. ,

( | | )

, PDF417 , . , $$$3:1$( , . 4). , $$$4:1$.

, PDF417 " ", 2 .

:

$$$H = N_rY + 2Q$
$$$W = (17N_c + 69)X + 2Q$

$$$H$— ;
$$$W$— ;
$$$N_r$— ;
$$$N_c$— ;
$$$Y$— ();
$$$X$— ;
$$$Q$— ( $$$2X$).

16. () PDF417

( | | )

PDF417 "" ( ), PDF417 (Truncated PDF417, . 9).

:

• ( , 06);
• - 1 .

34 15 :

$$$W = (17N_c + 35)X + 2Q$

. 9. PDF417 ( , )

, :

• , ;
• - .

17.

( | | )

PDF417

• US5243655A (Google Patents)
• ISO/IEC 15438:2015 ( , ISO)

• ASCII (Wikipedia)
• PC 437 (Wikipedia)
• ISO 8859-1 ( , ISO) — 8- PDF417. (Wikipedia)

• + (GitHub)

18.

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, PDF417. (, , ) , .

, step by step:

• PDF417 ( )
• Aztec Code

, , , ( PDF417).

, , - . , .

!

P.S. , , . "Ctrl / ⌘ + Enter", Ctrl / ⌘, . , . !