rdjpgcom(1) - phpMan

RDJPGCOM(1)                          General Commands Manual                          RDJPGCOM(1)

NAME
       rdjpgcom - display text comments from a JPEG file

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

DESCRIPTION
       rdjpgcom  reads  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, they are widely used to hold
       user-supplied text strings.  This lets you add annotations, titles, index  terms,  etc  to
       your  JPEG  files,  and later retrieve them as text.  COM blocks do not interfere with the
       image stored in the JPEG file.  The maximum size of a COM block is 64K, but you  can  have
       as many of them as you like in one JPEG file.

OPTIONS
       -raw   Normally  rdjpgcom  escapes non-printable characters in comments, for security rea-
              sons.  This option avoids that.

       -verbose Causes rdjpgcom to also display the JPEG image dimensions.

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

HINTS
       rdjpgcom does not depend on the IJG JPEG library.  Its source code is intended as  an  il-
       lustration of the minimum amount of code required to parse a JPEG file header correctly.

       In  -verbose mode, rdjpgcom will also attempt to print the contents of any "APP12" markers
       as text.  Some digital cameras produce APP12 markers containing  useful  textual  informa-
       tion.   If  you  like,  you can modify the source code to print other APPn marker types as
       well.

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

AUTHOR
       Independent JPEG Group

                                          02 April 2009                               RDJPGCOM(1)

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