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Corrected error-correction in Code 1

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Code 1 now uses correct Reed-Solomon error correction polynomials.
With thanks to Terry Burton.
This commit is contained in:
Robin Stuart 2011-03-07 12:55:22 +00:00
parent b36542b8f8
commit b30f8e110f
1 changed files with 1 additions and 22 deletions
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23
backend/code1.c
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@ -1200,29 +1200,8 @@ int code_one(struct zint_symbol *symbol, unsigned char source[], int length)
data_blocks = c1_blocks[size - 1];
/*
Section 2.2.5.1 states:
"The polynomial arithmetic... is calculated using bit-wise modulo 2 arithmetic
and byte-wise modulo 100101101 arithmetic (this is a Galois Field of 2^8 with
100101101 representing the field's prime modulus polynomial:
x^8 + x^5 + x^3 + x^2 + 1)."
This is the same as Data Matrix (ISO/IEC 16022) however the calculations in Appendix F
of the Code One specification do not agree with those in Annex E of ISO/IEC 16022.
For example Code One Appendix F states:
"The polynomial divisor for generating ten check characters for Version T-16
and Version A is:
g(x)=x^10 + 136x^9 + 141x^8 + 113x^7 + 76x^6 + 218x^5 + 43x^4 + 85x^3
+ 182x^2 + 31x + 52."
Whereas ISO/IEC 16022 Annex E states:
"The polynomial divisor for generating 10 check characters is:
g(x)=x^10 + 61x^9 + 110x^8 + 255x^7 + 116x^6 + 248x^5 + 223x^4 + 166x^3
+ 185x^2 + 24x + 28."
For this code I have assumed that ISO/IEC 16022 is correct and the USS Code One
specifications are incorrect
*/
rs_init_gf(0x12d);
rs_init_code(c1_ecc_blocks[size - 1], 1);
rs_init_code(c1_ecc_blocks[size - 1], 0);
for(i = 0; i < data_blocks; i++) {
for(j = 0; j < c1_data_blocks[size - 1]; j++) {