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)

-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

AUTHOR

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