Provided by: libjpeg-tools_0.0~git20220805.54ec643-1_amd64 bug

NAME

       jpeg - jpeg compressor

SYNOPSIS

       jpeg [options] source target

DESCRIPTION

       jpeg Copyright (C) 2012-2018 Thomas Richter, University of Stuttgart and Accusoft

       For license conditions, see README.license for details.

       default  is  to  decode  the  jpeg  input  and write a ppm output use -q [1..100] or -p to
       enforce encoding

       -q quality : selects the encoding mode and defines the quality of the base image

       -Q quality : defines the quality for the extension layer

       -quality q : use a profile and part specific weighting between base and extension

              layer quality

       -r         : enable the residual codestream for HDR and lossless

              coding, requires -q and -Q to define base and enhancement layer quality.

       -r12       : use a 12 bit residual image instead of an 8 bit residual

              image.

       -rl        : enforce a int-to-int lossless DCT in the residual domain

              for lossless coding enabled by -Q 100

       -ro        : disable the DCT in the residual domain, quantize spatially for

              near-lossless coding

       -ldr file  : specifies a separate file containing the base layer

              for encoding.

       -R bits    : specify refinement bits for the base images.

              This works like -r but in the DCT domain.

       -rR bits   : specify refinement bits for the residual image.

       -N         : enable noise shaping of the prediction residual

       -U         : disable automatic upsampling

       -l         : enable lossless coding without a residual image by an

              int-to-int DCT, also requires -c and -q 100 for true lossless

       -p         : JPEG lossless (predictive) mode

              also requires -c for true lossless

       -c         : disable the RGB to YCbCr decorrelation transformation

       -xyz       : indicates that the HDR image is in the XYZ colorspace

              note that the image is not *converted* to this space, but is assumed to be  encoded
              in this space.

       -cxyz      : similar to the above, but uses the dedicated C transformation

              to implement a XYZ colorspace conversion.

       -sp        : use separate LUTs for each component.

       -md        : use the median instead of the center of mass

              for constructing the inverse TMO of ISO/IEC 18477-7 profile C.

       -ct        : use the center of mass instead of the median

              for constructing the inverse TMO of ISO/IEC 18477-7 profile C.

       -sm iter   : use <iter> iterations to smooth out the histogram for

              inverse-TMO based algorithms. Default is not to smooth the histogram.

       -ncl       : disable clamping of out-of-gamut colors.

              this is automatically enabled for lossless.

       -m maxerr  : defines a maximum pixel error for JPEG LS coding

       -h         : optimize the Huffman tables

       -a         : use arithmetic coding instead of Huffman coding

              available for all coding schemes (-p,-v,-l and default)

       -bl        : force encoding in the baseline process, default is extended sequential

       -v         : use progressive instead of sequential encoding

              available for all coding schemes (-r,-a,-l and default)

       -qv        : use a simplified scan pattern for progressive that only

              separates AC from DC bands and may improve the performance

       -d         : encode the DC band only (requires -p)

       -y levels  : hierarchical JPEG coding with the given number of decomposition

              levels.  If levels is zero, then a lossless coding mode for hierarchical is used in
              which the second lossless scan encodes the DCT residuals of  the  first  scan.  For
              that,  -c  is suggested for true lossless. If levels is one, then the lossy initial
              scan is downscaled by a power of two.

       -g gamma   : define the exponent for the gamma for the LDR domain, or rather, for

              mapping HDR to LDR. A suggested value is 2.4  for  mapping  scRGB  to  sRBG.   This
              option  controls the base-nonlinearity that generates the HDR pre-cursor image from
              the LDR image. It is also used in the absence  of  -ldr  (i.e.  no  LDR  image)  to
              tonemap  the  HDR  input  image.   Use  -g  0  to use an approximate inverse TMO as
              base-nonlinearity, and for tonemapping with the Reinhard operator if the LDR  image
              is missing.

       -gf file   : define the inverse one-point L-nonlinearity on decoding from a file

              this  file  contains  one  (ASCII  encoded) digit per line, 256*2^h lines in total,
              where h is the number of refinement bits. Each line contains  an  (integer)  output
              value the corresponding input is mapped to.

       -z mcus    : define the restart interval size, zero disables it

       -n         : indicate the image height by a DNL marker

       -s WxH,... : define subsampling factors for all components

              note  that  these  are  NOT  MCU  sizes  Default  is  1x1,1x1,1x1 (444 subsampling)
              1x1,2x2,2x2 is the 420 subsampling often used

       -sr WxH,...: define subsampling in the residual domain

       -rs        : encode the residual image in sequential (rather than the modified residual)

              coding mode

       -rv        : encode the residual image in progressive coding mode

       -ol        : open loop encoding, residuals are based on original, not reconstructed

       -dz        : improved deadzone quantizer, may help to improve the R/D performance

       -oz        : optimize quantizer, may help to improve the R/D performance

       -dr        : include the optional de-ringing (Gibbs Phenomenon) filter on encoding

   -qt n      : define the quantization table. The following tables are currently defined:
              n = 0 the example tables from Rec. ITU-T T.81 | ISO/IEC 10918-1 (default) n =  1  a
              completely flat table that should be PSNR-optimal n = 2 a MS-SSIM optimized table n
              = 3 the table suggested by ImageMagick n = 4 a HSV-PSNR optimized table n =  5  the
              table from Klein, Silverstein and Carney:

              Relevance of human vision to JPEG-DCT compression (1992)

              n = 6 the table from Watson, Taylor, Borthwick:

              DCTune perceptual optimization of compressed dental X-Rays (1997)

              n = 7 the table from Ahumada, Watson, Peterson:

              A visual detection model for DCT coefficient quantization (1993)

              n = 8 the table from Peterson, Ahumada and Watson:

              An improved detection model for DCT coefficient quantization (1993)

       -qtf file  : read the quantization steps from a file, 64*2 integers (luma & chroma)

       -rqt n     : defines the quantization table for the residual stream in the same way

       -rqtf file : read the residual quantization steps from a file

       -al file   : specifies a one-component pgm/pfm file that contains an alpha component

              or  the  code will write the alpha component to.  This demo code DOES NOT implement
              compositing of alpha and background

       -am  mode    :  specifes  the  mode  of  the  alpha:  1  (regular)  2  (premultiplied)   3
       (matte-removal)

       -ab r,g,b  : specifies the matte (background) color for mode 3 as RGB triple

       -ar        : enable residual coding for the alpha channel, required if the

              alpha channel is larger than 8bpp

       -ar12      : use a 12 bit residual for the alpha channel

       -aR bits   : set refinement bits in the alpha base codestream

       -arR bits  : set refinement bits in the residual alpha codestream

       -aol       : enable open loop coding for the alpha channel

       -adz       : enable the deadzone quantizer for the alpha channel

       -aoz       : enable the quantization optimization for the alpha channel

       -adr       : include the de-ringing filter for the alpha channel

       -all       : enable lossless DCT for alpha coding

       -alo       : disable the DCT in the residual alpha channel, quantize spatially.

       -aq qu     : specify a quality for the alpha base channel (usually the only one)

       -aQ qu     : specify a quality for the alpha extension layer

       -aqt n     : specify the quantization table for the alpha channel

       -aqtf file : read the alpha quantization tables from a file

       -arqt n    : specify the quantization table for residual alpha

       -arqtf file: read the residual alpha quantization tables from a file

       -aquality q: specify a combined quality for both

       -ra        : enable arithmetic coding for residual image (*NOT SPECIFIED*)

       -ls mode   : encode in JPEG LS mode, where 0 is scan-interleaved,

              1  is  line  interleaved  and  2  is  sample  interleaved.   NOTE  THAT THIS IS NOT
              CONFORMING TO REC. ITU-T T.81 | ISO/IEC 10918 BUT COMPLIANT TO REC.  ITU-T  T.87  |
              ISO/IEC  14495-1  (JPEG-LS)  WHICH  IS  A DIFFERENT STANDARD.  Use -c to bypass the
              YCbCr color transformation for true lossless,  also  use  -c  for  decoding  images
              encoded  by  the UBC reference software as it does not write an indicator marker to
              disable the transformation itself.  Note that the UBC implementation will not  able
              to  decode  streams  created by this software due to a limitation of the UBC code -
              the streams are nevertheless fully conforming.

       -cls       : Use a JPEG LS part-2 conforming pseudo-RCT color transformation.

              Note that this transformation is only CONFORMING TO  REC.  ITU-T  T.870  |  ISO/IEC
              14495-2  AND  NOT  CONFORMING  TO  REC.  ITU-T  T.81  |  ISO/IEC 10918-1. Works for
              near-lossless JPEG LS DO NOT USE FOR LOSSY JPEG, it will also create artifacts.

EXAMPLES

       Standard JPEG compression, with 444 (aka "no") subsampling:

       $ jpeg -q <quality> infile.ppm outfile.jpg

       Standard JPEG compression, with 422 subsampling:

       $ jpeg -q <quality> -s 1x1,2x2,2x2 infile.ppm outfile.jpg

       Intermediate dynamic range compression, i.e. compression of images of a bit-depth  between
       8 and 16 bits:

       $ jpeg -r -q <base-quality> -Q <extension-quality> -h -r12 infile.ppm outfile.jpg

       This  type of encoding uses a technology known as "residual scans" which increase the bit-
       depths in the spatial domain which is enabled by  the  -r  command  line  switch.  The  -Q
       parameter  sets  the  quality  of  the  residual  image.   To improve the precision in the
       frequency domain, "refinement scans" can be used.  The following encodes  a  12-bit  image
       with  four additional refinement scans, enabled by the "-R 4" parameter.

       $ jpeg -q <quality> -R 4 -h infile.ppm outfile.jpg

       Both  technologies  can  be  combined,  and the precision of the residual scan can also be
       enlarged by using residual refinement scans with the -rR option.   The  following  command
       line with use a 12-bit residual scan with four refinement scans:

       $ jpeg -r -q <base-quality> -Q <extension-quality> -h -rR 4 infile.ppm outfile.jpg

       High-dynamic  range  compression allows three different profiles of varying complexity and
       performance. The profiles are denoted by "-profile  <X>"  where  <X>  is  a,b  or  c.  The
       following encodes an HDR image in profile C:

       $  jpeg  -r  -q  <base-quality>  -Q  <extension-quality>  -h  -profile  c -rR 4 infile.pfm
       outfile.jpg

       HDR images here have to be fed into the command line in "pfm" format.  exr or hdr  is  not
       supported  as input format and requires conversion to pfm first. pfm is the floating-point
       equivalent of ppm and encodes each pixel by three 32-bit floating point numbers.

       Encoding in profiles a and b works likewise, though it is generally advisable to use "open
       loop"  rather  than  "closed loop" coding for these two profiles by additionally providing
       the "-ol" parameter. This also works for profile C:

       $ jpeg -ol -r -profile a -q <base-quality> -Q <extension-quality> -h infile.pfm out.jpg

       similar for profile B.

       What is common to profiles A and C is that you may optionally also specify the LDR  image,
       i.e.  the  image  that  a legacy JPEG decoder will show. By default, a simple tone mapping
       algorithm ("global Reinhard") will be used to derive a suitable LDR image from  the  input
       image:

       $  jpeg  -ldr  infile.ppm  -q  <base-quality>  -Q  <extension-quality> -h -rR 4 infile.pfm
       out.jpg

       The profile is by default profile c, but it also works for profile a:

       $ jpeg -ol profile a -ldr infile.ppm -q <base-quality> -Q  <extension-quality>  infile.pfm
       out.jpg

       It  is  in  general  advisable for profile c encoding to enable residual refinement scans,
       profiles a or b do not require them.

       The following options exist for lossless coding integer:

       predictive Rec. ITU-T T.81  |  ISO/IEC  10918-1  coding.  Note,  however,  that  not  many
       implementations  are  capable  of  decoding  such stream, thus this is probably not a good
       option for all-day purposes.

       $ jpeg -p -c infile.ppm out.jpg

       While the result is a  valid  Rec.  ITU-T  T.81  |  ISO/IEC  10918-1  stream,  most  other
       implementations will hick up and break, thus it is not advisable to use it.

       A second option for lossless coding is residual coding within profile c:

       $ jpeg -q <quality> -Q 100 -h -r infile.ppm out.jpg

       This also works for floating point coding. Note that lossless coding is enabled by setting
       the extension quality to 100.

       $ jpeg -q <quality> -Q 100 -h -r infile.pfm out.jpg

       However, this is only lossless for 16 bit input samples, i.e. there is  a  precision  loss
       due  to  down-converting  the 32-bit input to 16 bit. If samples are out of the 601 gamut,
       the problem also exists that clamping will happen. To avoid that, encode in the XYZ  color
       space (profile C only, currently):

       $ jpeg -xyz -q <quality> -Q 100 -h -r infile.pfm out.jpg

       A  second option for lossless integer coding is to use a lossless 1-1 DCT process. This is
       enabled with the -l command line option:

       $ jpeg -l -q 100 -c infile.ppm out.jpg

       Refinement scans can be used to increase the sample precision to up to 12 bits.  The  "-c"
       command line option disables the lossy color transformation.

       Additionally,  this  implementation  also supports JPEG LS, which is outside of Rec. ITU-T
       T.81 | ISO/IEC 10918-1 and ISO/IEC 18477. For that, use the command line option -ls:

       $ jpeg -ls -c infile.ppm out.jpg

       The "-c" command line switch is necessary to disable the color transformation as  JPEG  LS
       typically encodes in RGB and not YCbCr space.

       Optionally,  you  may  specify  the  JPEG  LS "near" parameter (maximum error) with the -m
       command line switch:

       $ jpeg -ls -m 2 -c infile.ppm out.jpg

       JPEG LS also specifies a lossless color transformation that is enabled with -cls:

       $ jpeg -ls -cls infile.ppm out.jpg

       To encode images with an alpha channel, specify the source image that contains  the  alpha
       channel with -al. The alpha channel is a one-component grey-scale image, either integer or
       floating point. The quality of the alpha channel  is  specified  with  -aq,  that  of  the
       regular image with -q:

       $ jpeg -al alpha.pgm -aq 80 -q 85 input.ppm output.jpg

       Alpha  channels  can be larger than 8bpp or can be floating point. In both cases, residual
       coding is required. To enable residual coding in the alpha channel, use  the  -ar  command
       line  option. Similar to the regular image, where residual coding requires two parameters,
       -q for the base quality and -Q for the extension  quality,  an  alpha  channel  that  uses
       residual  coding  also  requires a base and extension quality, the former is given by -aq,
       the latter with -aQ:

       $ jpeg -ar -al alphahigh.pgm -q 85 -Q 90 -aq 80 -aQ 90 input.ppm out.jpg

       The alpha channel can be encoded without loss if desired. For that, enable residual coding
       with -ar and specify an extension quality of 100:

       $ jpeg -ar -al alphahigh.pgm -q 85 -Q 90 -aq 80 -aQ 100 input.ppm out.jpg

       The  alpha  channel can use the same technology extensions as the image, namely refinement
       scans in the base or extension image, or 12-bit residual images. The number of  refinement
       scans  is  selected  with  -aR and -arR for the base and residual image, a 12-bit residual
       image is selected with -ar12.

       --------------------------------------------------------------------------

       Decoding is much simpler:

       $ jpeg infile.jpg out.ppm

       or, for floating point images:

       $ jpeg infile.jpg out.pfm

       If you want to decode a JPEG LS image, then you may want to tell the decoder explicitly to
       disable the color transformation even though the corresponding marker signalling coding in
       RGB space is typically missing for JPEG LS:

       $ jpeg -c infile.jpg out.ppm

       If an alpha channel is included in the  image,  the  decoder  does  not  reconstruct  this
       automatically, nor does it attempt to merge the alpha image into the file. Instead, it may
       optionally be instructed to write the alpha channel into  a  separate  1-component  (grey-
       scale) file:

       $ jpeg -al alpha.pgm infile.jpg outfile.ppm

       The -al option for the decoder provides the target file for the alpha channel.

AUTHOR

       This  manual  page  was  written  by  Mathieu  Malaterre <malat@debian.org> for the Debian
       GNU/Linux system (but may be used by others).