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MAN page from CentOS 7 mozjpeg-master-20170714.2.x86_64.rpm

RDJPGCOM

Section: User Commands (1)
Updated: 02 April 2009
Index 

NAME

rdjpgcom - display text comments from a JPEG file 

SYNOPSIS

rdjpgcom[-raw][-verbose][filename]

 

DESCRIPTION

rdjpgcomreads the named JPEG/JFIF file, or the standard input if no file is named,and prints any text comments found in the file on the standard output.

The JPEG standard allows "comment" (COM) blocks to occur within a JPEG file.Although the standard doesn't actually define what COM blocks are for, theyare widely used to hold user-supplied text strings. This lets you addannotations, titles, index terms, etc to your JPEG files, and later retrievethem as text. COM blocks do not interfere with the image stored in the JPEGfile. The maximum size of a COM block is 64K, but you can have as many ofthem as you like in one JPEG file. 

OPTIONS

-raw
Normallyrdjpgcomescapes non-printable characters in comments, for security reasons.This option avoids that.

-verboseCausesrdjpgcomto also display the JPEG image dimensions.

Switch names may be abbreviated, and are not case sensitive. 

HINTS

rdjpgcomdoes not depend on the IJG JPEG library. Its source code is intended as anillustration of the minimum amount of code required to parse a JPEG fileheader correctly.

In-verbosemode,rdjpgcomwill also attempt to print the contents of any "APP12" markers as text.Some digital cameras produce APP12 markers containing useful textualinformation. If you like, you can modify the source code to printother APPn marker types as well. 

SEE ALSO

cjpeg(1),djpeg(1),jpegtran(1),wrjpgcom(1) 

AUTHOR

Independent JPEG Group


 

Index

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
HINTS
SEE ALSO
AUTHOR

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