# phpman > perldoc > Image::ExifTool::JPEGDigest

## NAME
    [Image::ExifTool::JPEGDigest](https://www.chedong.com/phpMan.php/perldoc/Image%3A%3AExifTool%3A%3AJPEGDigest/markdown) - Calculate JPEGDigest and JPEGQualityEstimate

## SYNOPSIS
    This module is used by [Image::ExifTool](https://www.chedong.com/phpMan.php/perldoc/Image%3A%3AExifTool/markdown)

## DESCRIPTION
    This module contains a lookup for values of the JPEG DQT digest, allowing some image
    identification from JPEG data alone. It also calculates an estimated JPEG quality if requested.

## AUTHOR
    Copyright 2003-2022, Phil Harvey (philharvey66 at gmail.com)

    This library is free software; you can redistribute it and/or modify it under the same terms as
    Perl itself.

## REFERENCES
    <<https://github.com/ImageMagick/ImageMagick/blob/master/coders/jpeg.c>>

## ACKNOWLEDGEMENTS
    Thanks to Jens Duttke for most of the work that went into this module, and to Franz Buchinger
    for the values he added.

## SEE ALSO
    "JPEG Tags" in [Image::ExifTool::TagNames](https://www.chedong.com/phpMan.php/perldoc/Image%3A%3AExifTool%3A%3ATagNames/markdown), Image::[ExifTool(3pm)](https://www.chedong.com/phpMan.php/man/ExifTool/3pm/markdown)