Line Length

word

Number of pixels per line

 

 

1728: standard fax G3

 

 

2048: B4 (optional)

 

 

2432: A3 (optional)

 

 

Support for additional values is optional for COMMON-

 

 

ISDN-API

 

 

If FAX paper formats and resolutions are enabled

 

 

1728: ISO A4 at R8 x 3.85, R8 x 7.7, R8 x 15.4, 200 x 200

 

 

2048: ISO B4 at R8 x 3.85, R8 x 7.7, R8 x 15.4, 200 x 200

 

 

2432: ISO A3 at R8 x 3.85, R8 x 7.7, R8 x 15.4, 200 x 200

 

 

2592: ISO A4 at 300 x 300, 300 x 600

 

 

3072: ISO B4 at 300 x 300, 300 x 600

 

 

3648: ISO A3 at 300 x 300, 300 x 600

 

 

3456: ISO A4 at R16 x 15.4, 400 x 400, 400 x 800

 

 

4096: ISO B4 at R16 x 15.4, 400 x 400, 400 x 800

 

 

4864: ISO A3 at R16 x 15.4, 400 x 400, 400 x 800

 

 

5184: ISO A4 at 600 x 600, 600 x 1200

 

 

6144: ISO B4 at 600 x 600, 600 x 1200

 

 

7296: ISO A3 at 600 x 600, 600 x 1200

 

 

10368: ISO A4 at 1200 x 1200

 

 

12288: ISO B4 at 1200 x 1200

 

 

14592: ISO A3 at 1200 x 1200

Page Length

word

Number of pixel lines per page. If not known, coded as

 

 

0x0000.

OffsetPreviousPage

dword

Byte offset to previous page header or 0x00000000. Coded as

 

 

0x00000001 if first page.

OffsetNextPage

dword

Byte offset to next page header or 0x00000000. Coded as

 

 

0x00000001 if last page.

B.2.3 Page data

Page data are coded line by line: data describes each pixel row. Lines are coded as records of variable length; each line is coded according to the element coding in the page header. At present, only modified Huffman coding is supported. MH coding is bit-oriented: the pixel bits are stored in the bits of code words least significant first. No EOL code words or fill bits are included. If the data include EOL code words, COMMON-ISDN-APIignores these.

Each record is identified by the first byte:

•1...216: a pixel row with 1...216 MH-coded bytes follows immediately

•0: escape code for a pixel row with more than 216 MH-coded bytes. In this case, the following word in the range 218...32767 defines the number of MH-coded bytes which follow.

•217...253: white space, skip 1...37 empty lines

•254: start of page header (see above)

•255: if followed by a byte with value 0, illegal line coding. Applications may choose whether to interpret this line as empty or as a copy of the previous line. If this byte is followed by a byte with a value 1...255, then 1...255 bytes of additional user information follow (reserved for future extensions).

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