# phpman > perldoc > Font::TTF::Vmtx

## NAME
    [Font::TTF::Vmtx](https://www.chedong.com/phpMan.php/perldoc/Font%3A%3ATTF%3A%3AVmtx/markdown) - Vertical Metrics

## DESCRIPTION
    Contains the advance height and top side bearing for each glyph. Given the compressability of
    the data onto disk, this table uses information from other tables, and thus must do part of its
    output during the output of other tables

## INSTANCE VARIABLES
    The vertical metrics are kept in two arrays by glyph id. The variable names do not start with a
    space

    advance
        An array containing the advance height for each glyph

    top An array containing the top side bearing for each glyph

## METHODS
  $t->read
    Reads the vertical metrics from the TTF file into memory

  $t->out($fh)
    Writes the metrics to a TTF file. Assumes that the "vhea" has updated the numVMetrics from here

## BUGS
    None known

## AUTHOR
    Martin Hosken <<http://scripts.sil.org/FontUtils>>.

## LICENSING
    Copyright (c) 1998-2016, SIL International (<http://www.sil.org>)

    This module is released under the terms of the Artistic License 2.0. For details, see the full
    text of the license in the file LICENSE.