# TIFF Tag T4Options

IFD | Image | |
---|---|---|

Code | 292 (hex 0x0124) | |

Name | T4Options | |

LibTiff name | TIFFTAG_GROUP3OPTIONS | |

Type | LONG | |

Count | 1 | |

Default | 0 (basic 1-dimensional coding) |

# Description

Options for Group 3 Fax compression

This field is made up of a set of 32 flag bits. Unused bits must be set to 0. Bit 0 is the low-order bit.

The specification defines these bits:

Bit 0 is 1 for 2-dimensional coding (otherwise 1-dimensional is assumed). For 2-D coding, if more than one strip is specified, each strip must begin with a 1-dimensionally coded line. That is,
RowsPerStrip should be a multiple of Parameter K, as documented in the CCITT specification.

Bit 1 is 1 if uncompressed mode is used.

Bit 2 is 1 if fill bits have been added as necessary before EOL codes such that EOL always ends on a byte boundary, thus ensuring an EOL-sequence of 1 byte preceded by a zero nibble: xxxx-0000
0000-0001.

LibTiff defines these bits as follows:

GROUP3OPT_2DENCODING = 1;

GROUP3OPT_UNCOMPRESSED = 2;

GROUP3OPT_FILLBITS = 4;