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62 lines
1.3 KiB
C
62 lines
1.3 KiB
C
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/* Fax G3/G4 tables */
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/*
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<raph> the first 2^(initialbits) entries map bit patterns to decodes
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<raph> let's say initial_bits is 8 for the sake of example
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<raph> and that the code is 1001
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<raph> that means that entries 0x90 .. 0x9f have the entry { val, 4 }
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<raph> because those are all the bytes that start with the code
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<raph> and the 4 is the length of the code
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... if (n_bits > initial_bits) ...
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<raph> anyway, in that case, it basically points to a mini table
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<raph> the n_bits is the maximum length of all codes beginning with that byte
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<raph> so 2^(n_bits - initial_bits) is the size of the mini-table
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<raph> peter came up with this, and it makes sense
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*/
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typedef struct cfd_node_s cfd_node;
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struct cfd_node_s
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{
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short val;
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short nbits;
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};
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enum
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{
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cfd_white_initial_bits = 8,
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cfd_black_initial_bits = 7,
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cfd_2d_initial_bits = 7,
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cfd_uncompressed_initial_bits = 6 /* must be 6 */
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};
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/* non-run codes in tables */
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enum
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{
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ERROR = -1,
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ZEROS = -2, /* EOL follows, possibly with more padding first */
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UNCOMPRESSED = -3
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};
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/* semantic codes for cf_2d_decode */
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enum
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{
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P = -4,
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H = -5,
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VR3 = 0,
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VR2 = 1,
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VR1 = 2,
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V0 = 3,
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VL1 = 4,
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VL2 = 5,
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VL3 = 6
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};
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/* Decoding tables */
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extern const cfd_node cf_white_decode[];
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extern const cfd_node cf_black_decode[];
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extern const cfd_node cf_2d_decode[];
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extern const cfd_node cf_uncompressed_decode[];
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