44 lines
2.1 KiB
Groff
44 lines
2.1 KiB
Groff
--- jpegtran.1.orig 2009-03-28 19:18:21.000000000 +0100
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+++ jpegtran.1 2009-07-01 09:19:36.000000000 +0200
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@@ -195,6 +195,14 @@
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Copy all extra markers. This setting preserves miscellaneous markers
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found in the source file, such as JFIF thumbnails, Exif data, and Photoshop
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settings. In some files these extra markers can be sizable.
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+See 'EXIF FILES' for special tratement of EXIF markers.
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+.TP
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+.B \-copy exif
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+This setting preserves the EXIF marker, commonly found in JPEG files produced
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+by digital cameras, in addition to any comment markers. If there is an EXIF
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+marker it is copied and the JFIF marker (incompatible with EXIF) is
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+omitted. If there is no EXIF marker a JFIF one is emitted as usual. See 'EXIF
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+FILES' for special tratement of EXIF markers.
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.IP
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The default behavior is
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.BR "\-copy comments" .
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@@ -223,6 +231,26 @@
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.B \-debug
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Same as
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.BR \-verbose .
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+.SH EXIF FILES
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+The EXIF variety of JPEG files, which are often produced by digital cameras,
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+are recognized by jpegtran as EXIF files (i.e. not as JFIF, the
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+usual variety of JPEG files). If the input file is recognized as EXIF (i.e.,
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+there is an EXIF marker and no JFIF marker) the '-copy exif' option is
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+automatically turned on if '-copy comments', or no '-copy' option, was
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+specified. Thus, unless '-copy none' is specified an EXIF file is kept as EXIF
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+and not converted to JFIF.
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+.PP
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+If a geometrical transformation is applied (e.g., rotate, transpose) the EXIF
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+width and height fields are set to the width and height of the output
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+image. Furthermore, the orientation field is reset to one, meaning tha the
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+orientation of the output image is upright (i.e. normal).
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+.PP
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+Note that an explicitely given '-copy exif' option will output an EXIF file if
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+the input is an EXIF file that was saved as JFIF, and that the EXIF marker is
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+still present. This option is useful for recovering EXIF files that where
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+converted to JFIF by a non EXIF-aware software. Note however, that the data in
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+the EXIF marker is not validated, unless a geometrical transformation is
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+applied.
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.SH EXAMPLES
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.LP
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This example converts a baseline JPEG file to progressive form:
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