68 lines
2.7 KiB
Groff
68 lines
2.7 KiB
Groff
--- jpegtran.1.orig Sun Aug 3 16:01:01 1997
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+++ jpegtran.1 Fri Oct 8 14:51:56 2004
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@@ -71,12 +71,23 @@
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.PP
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The image can be losslessly transformed by giving one of these switches:
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.TP
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+.B \-crop WxH+X+Y
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+Crop to a rectangular subarea of width W, height H starting at point X,Y.
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+Allows the Width and or Height of the image to exceed the image.
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+.TP
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+.B \-drop +X+Y
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+Drop another image. Overlay part of the source image at point width
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+W + height H.
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+.TP
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.B \-flip horizontal
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Mirror image horizontally (left-right).
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.TP
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.B \-flip vertical
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Mirror image vertically (top-bottom).
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.TP
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+.B \-perfect
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+Fails with an error if there is any loss durring the transformation.
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+.TP
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.B \-rotate 90
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Rotate image 90 degrees clockwise.
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.TP
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@@ -161,6 +172,14 @@
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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 and Photoshop settings.
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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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.PP
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The default behavior is
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.BR "\-copy comments" .
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@@ -189,6 +208,26 @@
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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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