'\" te
.TH jpegtran 1 "26 Mar 2004" "SunOS 5.11" "User Commands"
.SH "NAME"
jpegtran \- lossless
transformation of JPEG files
.SH "SYNOPSIS"
.PP
\fBjpegtran\fR [\fB\fIoptions\fR\fR] [\fB\fIfilename\fR\fR]
.SH "DESCRIPTION"
.PP
\fBjpegtran\fR performs various useful transformations of
JPEG files\&. \fBjpegtran\fR can translate the coded representation
from one variant of JPEG to another, for example from baseline JPEG to progressive
JPEG or vice versa\&. \fBjpegtran\fR can also perform some rearrangements
of the image data, for example turning an image from landscape to portrait
format by rotation\&.
.PP
\fBjpegtran\fR works by rearranging the compressed data (DCT
coefficients), without ever fully decoding the image\&. Therefore, \fBjpegtran\fR
transformations are lossless: there is no image degradation at all, which
would not be true if you used \fBdjpeg\fR followed by \fBcjpeg\fR to accomplish the same conversion\&. However, \fBjpegtran\fR
cannot perform lossy operations such as changing the image quality\&.
.PP
\fBjpegtran\fR reads the named JPEG/JFIF file, or the standard
input if no file is named, and produces a JPEG/JFIF file on the standard output\&.
.SH "OPTIONS"
.PP
All options may be abbreviated\&. For example, -\fBoptimize\fR
may be written -\fBopt\fR or -\fBo\fR\&. Upper and lower
case are equivalent\&. British spellings are also accepted\&. For example, -\fBoptimise\fR\&.
.PP
The following options are supported:
.sp
.ne 2
.mk
\fB-\fBcopy all\fR\fR
.in +24n
.rt
Copy all
extra markers\&. This option preserves miscellaneous markers found in the source
file, such as JFIF thumbnails and source-application settings\&. In some files,
these extra markers can be sizable\&.
.sp
.sp 1
.in -24n
.sp
.ne 2
.mk
\fB-\fBcopy comments\fR\fR
.in +24n
.rt
Copy only comment markers\&. This option copies comments from the source file,
but discards any other inessential data\&. This is the default\&.
.sp
.sp 1
.in -24n
.sp
.ne 2
.mk
\fB-\fBcopy none\fR\fR
.in +24n
.rt
Copy
no extra markers from the source file\&. This option suppresses all comments
and other excess information present in the source file\&.
.sp
.sp 1
.in -24n
.sp
.ne 2
.mk
\fB-\fBflip horizontal\fR\fR
.in +24n
.rt
Create a mirror image horizontally, that is, from left to right\&. This is a
lossless transformation\&.
.sp
.sp 1
.in -24n
.sp
.ne 2
.mk
\fB-\fBflip vertical\fR\fR
.in +24n
.rt
Create a mirror image vertically, that is, from top to bottom\&. This is a lossless
transformation\&.
.sp
.sp 1
.in -24n
.sp
.ne 2
.mk
\fB-\fBgrayscale\fR\fR
.in +24n
.rt
Force
grayscale output\&. This is not a lossless transformation\&. For more information
about the -\fBgrayscale\fR option, see the Extended Description
section\&.
.sp
.sp 1
.in -24n
.sp
.ne 2
.mk
\fB-\fBmaxmemory \fIN\fR\fR\fR
.in +24n
.rt
Set the limit for the amount of memory to use in processing
large images\&. \fIN\fR is specified in thousands of bytes,
or in millions of bytes if "M" is specified with the number\&. For example, -\fBmax 4m\fR selects 4000000 bytes\&. If more space is needed, temporary
files are used\&.
.sp
.sp 1
.in -24n
.sp
.ne 2
.mk
\fB-\fBoptimize\fR\fR
.in +24n
.rt
Optimize
the entropy encoding parameters\&. For more information about the -\fBoptimize\fR option, see \fBcjpeg\fR(1)\&.
.sp
.sp 1
.in -24n
.sp
.ne 2
.mk
\fB-\fBoutfile \fIname\fR\fR\fR
.in +24n
.rt
Send the output image to the named file, instead of to the
standard output\&.
.sp
.sp 1
.in -24n
.sp
.ne 2
.mk
\fB-\fBprogressive\fR\fR
.in +24n
.rt
Create
a progressive JPEG file\&. For more information about the -\fBprogressive\fR option, see \fBcjpeg\fR(1)\&.
.sp
.sp 1
.in -24n
.sp
.ne 2
.mk
\fB-\fBrestart \fIN\fR\fR\fR
.in +24n
.rt
Emit a JPEG restart marker every \fIN\fR
MCU rows, or every \fIN\fR MCU blocks if "B" is specified
with the number\&. For more information about the -\fBrestart\fR option,
see \fBcjpeg\fR(1)\&.
.sp
.sp 1
.in -24n
.sp
.ne 2
.mk
\fB-\fBrotate 90\fR\fR
.in +24n
.rt
Rotate
the image 90 degrees clockwise\&. This is a lossless transformation\&.
.sp
.sp 1
.in -24n
.sp
.ne 2
.mk
\fB-\fBrotate 180\fR\fR
.in +24n
.rt
Rotate
the image 180 degrees clockwise\&. This is a lossless transformation\&.
.sp
.sp 1
.in -24n
.sp
.ne 2
.mk
\fB-\fBrotate 270\fR\fR
.in +24n
.rt
Rotate
the image 270 degrees clockwise, or 90 degrees anticlockwise\&. This is a lossless
transformation\&.
.sp
.sp 1
.in -24n
.sp
.ne 2
.mk
\fB-\fBscans \fIfile\fR\fR\fR
.in +24n
.rt
Use the scan script provided in the specified text file\&.
.sp
.sp 1
.in -24n
.sp
.ne 2
.mk
\fB-\fBtranspose\fR\fR
.in +24n
.rt
Transpose
the image, that is, across the UL-to-LR axis\&. This is a lossless transformation\&.
For more information about the -\fBtranspose\fR option, see the
Extended Description section\&.
.sp
.sp 1
.in -24n
.sp
.ne 2
.mk
\fB-\fBtransverse\fR\fR
.in +24n
.rt
Transverse
transpose the image, that is, across the UR-to-LL axis\&. This is a lossless
transformation\&.
.sp
.sp 1
.in -24n
.sp
.ne 2
.mk
\fB-\fBtrim\fR\fR
.in +24n
.rt
Drop non-transformable
edge blocks\&. This is not a lossless transformation\&. For more information about
the -\fBtrim\fR option, see the Extended Description section\&.
.sp
.sp 1
.in -24n
.sp
.ne 2
.mk
\fB-\fBverbose\fR\fR
.in +24n
.rt
Display
version information at startup, and enable debug printout\&. The -\fBvv\fR option displays more verbose output than the -\fBv\fR
option\&. The -\fBvvv\fR option displays the most verbose output\&.
.sp
You can also use -\fBdebug\fR to specify this option\&.
.sp
.sp 1
.in -24n
.SH "OPERANDS"
.PP
The following operands are supported:
.sp
.ne 2
.mk
\fB\fB\fIfilename\fR\fR\fR
.in +24n
.rt
The name of the JPEG file to be transformed\&.
.sp
.sp 1
.in -24n
.SH "EXTENDED DESCRIPTION"
.PP
If you do not specify one of the following options, you get a plain
baseline-JPEG output file: -\fBoptimize\fR, -\fBprogressive\fR, -\fBrestart \fIN\fR\fR, -\fBscans \fIfile\fR\fR\&. In such cases, the quality
setting and other settings are determined by the input file\&.
.SS "Lossless Transformations"
.PP
The transpose transformation has no restrictions as regards image dimensions\&.
The other transformations operate rather oddly if the image dimensions are
not a multiple of the iMCU siz, usually 8 or 16 pixels, because they can only
transform complete blocks of DCT coefficient data in the desired way\&. The
default behavior when transforming an odd-size image is designed to preserve
exact reversibility and mathematical consistency of the transformation set\&.
.PP
As stated, transpose can flip the entire image area\&. Horizontal mirroring
leaves any partial iMCU column at the right edge untouched, but is able to
flip all rows of the image\&. Similarly, vertical mirroring leaves any partial
iMCU row at the bottom edge untouched, but is able to flip all columns\&.
.PP
The other transforms can be built up as sequences of transpose and flip
operations\&. For consistency, their actions on edge pixels are defined to be
the same as the end result of the corresponding transpose-and-flip sequence\&.
.SS "Not-Lossless Transformations"
.PP
You may prefer to discard any untransformable edge pixels rather than
have a strange-looking strip along the right or bottom edges of a transformed
image\&. To do this, use the -\fBtrim\fR option\&. Obviously, a transformation
with -\fBtrim\fR is not reversible, so strictly speaking \fBjpegtran\fR
with this option is not lossless\&. Also, the expected mathematical equivalences
between the transformations no longer hold\&. For example, -\fBrot 270\fR -\fBtrim\fR trims only the bottom edge, but -\fBrot 90\fR -\fBtrim\fR followed by -\fBrot 180\fR -\fBtrim\fR trims
both edges\&.
.PP
Another not-strictly-lossless transformation option is -\fBgrayscale\fR\&. This option discards the chrominance channels if the input image
is YCbCr (that is, a standard color JPEG), which results in a grayscale JPEG
file\&. The luminance channel is preserved exactly, so this is a better method
of reducing to grayscale than decompression, conversion, and recompression\&.
The -\fBgrayscale\fR option is particularly useful for fixing a
monochrome picture that was mistakenly encoded as a color JPEG\&. In such a
case, the space saved by discarding the near-empty chrominance channels is
not large, but the decoding time for a grayscale JPEG is substantially less
than that for a color JPEG\&.
.SH "EXAMPLES"
.PP
\fBExample 1: Converting a Baseline JPEG File to Progressive Form\fR
.PP
.PP
.nf
example% \fBjpegtran -progressive test\&.jpg > testprog\&.jpg\fR
.fi
.PP
\fBExample 2: Rotating an Image 90 Degrees Clockwise, Discarding Any Unrotatable
Edge Pixels\fR
.PP
.PP
.nf
example% \fBjpegtran rot 90 -trim test\&.jpg > test90\&.jpg\fR
.fi
.SH "ENVIRONMENT VARIABLES"
.PP
\fBjpegtran\fR uses the following environment variables:
.sp
.ne 2
.mk
\fBJPEGMEM\fR
.in +24n
.rt
The value of this environment
variable, if set, is the default memory limit\&. The value is specified as described
for the -\fBmaxmemory\fR option\&. JPEGMEM overrides the default value
specified when the program was compiled, and is in turn overridden by an explicit -\fBmaxmemory\fR option\&.
.sp
.sp 1
.in -24n
.SH "ATTRIBUTES"
.PP
See \fBattributes\fR(5)
for descriptions of the following attributes:
.sp
.TS
tab() allbox;
cw(2.750000i)| cw(2.750000i)
lw(2.750000i)| lw(2.750000i).
ATTRIBUTE TYPEATTRIBUTE VALUE
Availabilityimage/library/libjpeg
Interface stabilityUncommitted
.TE
.sp
.SH "SEE ALSO"
.PP
Wallace, Gregory K\&., \fIThe JPEG Still Picture Compression Standard\fR Communications of the ACM, April 1991 (vol\&. 34, no\&. 4), pp\&. 30-44\&.
.PP
\fBcjpeg\fR(1), \fBdjpeg\fR(1), \fBrdjpgcom\fR(1), \fBwrjpgcom\fR(1)
.SH "NOTES"
.PP
Arithmetic coding is not supported\&. 
.PP
The entire image is read into memory and then written out again, even
in cases where this is not really necessary\&. Expect swapping on large images,
especially when using the more complex transform options\&.
.PP
This man page was originally written by the Independent JPEG Group\&.
Updated by Breda McColgan, Sun Microsystems Inc\&., 2004\&. 
...\" created by instant / solbook-to-man, Thu 20 Mar 2014, 02:30
...\" LSARC 2003/085 libtiff, libjpeg, and libpng