jpayne@68: .TH RDJPGCOM 1 "13 September 2013"
jpayne@68: .SH NAME
jpayne@68: rdjpgcom \- display text comments from a JPEG file
jpayne@68: .SH SYNOPSIS
jpayne@68: .B rdjpgcom
jpayne@68: [
jpayne@68: .B \-raw
jpayne@68: ]
jpayne@68: [
jpayne@68: .B \-verbose
jpayne@68: ]
jpayne@68: [
jpayne@68: .I filename
jpayne@68: ]
jpayne@68: .LP
jpayne@68: .SH DESCRIPTION
jpayne@68: .LP
jpayne@68: .B rdjpgcom
jpayne@68: reads the named JPEG/JFIF file, or the standard input if no file is named,
jpayne@68: and prints any text comments found in the file on the standard output.
jpayne@68: .PP
jpayne@68: The JPEG standard allows "comment" (COM) blocks to occur within a JPEG file.
jpayne@68: Although the standard doesn't actually define what COM blocks are for, they
jpayne@68: are widely used to hold user-supplied text strings.  This lets you add
jpayne@68: annotations, titles, index terms, etc to your JPEG files, and later retrieve
jpayne@68: them as text.  COM blocks do not interfere with the image stored in the JPEG
jpayne@68: file.  The maximum size of a COM block is 64K, but you can have as many of
jpayne@68: them as you like in one JPEG file.
jpayne@68: .SH OPTIONS
jpayne@68: .TP
jpayne@68: .B \-raw
jpayne@68: Normally
jpayne@68: .B rdjpgcom
jpayne@68: escapes non-printable characters in comments, for security reasons.
jpayne@68: This option avoids that.
jpayne@68: .PP
jpayne@68: .B \-verbose
jpayne@68: Causes
jpayne@68: .B rdjpgcom
jpayne@68: to also display the JPEG image dimensions.
jpayne@68: .PP
jpayne@68: Switch names may be abbreviated, and are not case sensitive.
jpayne@68: .SH HINTS
jpayne@68: .B rdjpgcom
jpayne@68: does not depend on the IJG JPEG library.  Its source code is intended as an
jpayne@68: illustration of the minimum amount of code required to parse a JPEG file
jpayne@68: header correctly.
jpayne@68: .PP
jpayne@68: In
jpayne@68: .B \-verbose
jpayne@68: mode,
jpayne@68: .B rdjpgcom
jpayne@68: will also attempt to print the contents of any "APP12" markers as text.
jpayne@68: Some digital cameras produce APP12 markers containing useful textual
jpayne@68: information.  If you like, you can modify the source code to print
jpayne@68: other APPn marker types as well.
jpayne@68: .SH SEE ALSO
jpayne@68: .BR cjpeg (1),
jpayne@68: .BR djpeg (1),
jpayne@68: .BR jpegtran (1),
jpayne@68: .BR wrjpgcom (1)
jpayne@68: .SH AUTHOR
jpayne@68: Independent JPEG Group