Adding upstream version 4.22.0.upstream/4.22.0

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 339 insertions, 0 deletions

diff --git a/upstream/debian-unstable/man1/pnmgamma.1 b/upstream/debian-unstable/man1/pnmgamma.1
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+\
+.\" This man page was generated by the Netpbm tool 'makeman' from HTML source.
+.\" Do not hand-hack it!  If you have bug fixes or improvements, please find
+.\" the corresponding HTML page on the Netpbm website, generate a patch
+.\" against that, and send it to the Netpbm maintainer.
+.TH "Pnmgamma User Manual" 1 "30 June 2007" "netpbm documentation"
+
+.SH NAME
+pnmgamma - perform gamma adjustment on a PNM image
+
+.UN synopsis
+.SH SYNOPSIS
+.PP
+\fBpnmgamma\fP
+{
+ \fB-bt709tolinear\fP | 
+ \fB-lineartobt709\fP |
+ \fB-bt709tosrgb\fP | 
+ \fB-srgbtobt709\fP
+}
+[\fB-gamma=\fP\fIfloat\fP]
+[\fB-rgamma=\fP\fIfloat\fP]
+[\fB-ggamma=\fP\fIfloat\fP]
+[\fB-bgamma=\fP\fIfloat\fP]
+
+[\fIpnmfile\fP]
+.PP
+\fBpnmgamma \fP
+[
+ \fB-bt709ramp\fP |
+ \fB-srgbramp\fP 
+]
+[\fB-ungamma\fP]
+[{\fIgamma\fP | \fIredgamma\fP \fIgreengamma\fP \fIbluegamma\fP}
+[\fIpnmfile\fP]]
+
+
+.UN description
+.SH DESCRIPTION
+.PP
+This program is part of
+.BR "Netpbm" (1)\c
+\&.
+.PP
+\fBPnmgamma\fP performs gamma adjustment on pseudo-PNM images.
+.PP
+The PPM format specification specifies that certain sample values
+in a file represent certain light intensities in an image.  In
+particular, they specify that the sample values are directly
+proportional to luminance as defined by ITU-R Recommendation BT.709.
+BT.709 luminance as a function of radiance is a power function
+modified with a linear ramp near black.
+.PP
+However, people sometimes work with approximations of PPM and PGM
+where the sample values represent intensity in different ways:
+.PP
+In one common variation, the sample value is directly proportional
+to radiance (often called "linear intensity").
+.PP
+Another popular variation is to make the samples proportional to
+luminance as defined by the International Electrotechnical Commission
+(IEC) SRGB standard.  The SRGB gamma transfer function is like the
+BT.709 one except with different constants in it.
+.PP
+Note that SRGB is often spelled "sRGB".  In this
+document, we use standard English typography, though, which doesn't
+allow for that kind of capitalization.
+.PP
+\fBpnmgamma\fP allows you to manipulate the gamma transfer
+function, thus working with and/or creating pseudo-PPM files that are
+useful for various things.
+.PP
+For example, if you feed a true PPM to \f(CWpnmgamma -bt709tolinear
+\fP, you get as output a file which is PPM in every respect except
+that the sample values are radiances.  If you feed such a file to
+\f(CWpnmgamma -linearto709\fP, you get back a true PPM.
+.PP
+The situation for PGM images is analogous.  And \fBpnmgamma\fP
+treats PBM images as PGM images.
+.PP
+When you feed a radiance-proportional pseudo-PPM image to a display
+program that expects a true PPM, the display appears darker than it
+should, so \fBpnmgamma\fP has the effect of lightening the image.
+When you feed a true PPM to a display program that expects
+radiance-proportional sample values, and therefore does a gamma
+adjustment of its own on them, the display appears lighter than it
+should, so \fBpnmgamma\fP with a gamma value less than one (the
+multiplicative inverse of whatever gamma value the display program
+uses) has the effect of darkening the image.
+
+.UN parameters
+.SH PARAMETERS
+.PP
+The form of the parameters depends on whether you're using the old
+syntax or the new syntax.  With the old syntax, the parameters are
+a mixture of gamma values and the input file name.  With the new
+syntax, the only parameter is the input file name and you specify gamma
+values with option.
+.PP
+You use the old syntax if you specify \fB-bt709ramp\fP (or
+its synonym \fB-cieramp\fP) or \fB-srgramp\fP or if you don't specify
+any transfer function at all (and thus default to a simple exponential).
+Otherwise, you use the new syntax.
+.PP
+With the old syntax, you may specify a single gamma value or 3
+separate gamma values (red, green, and blue) or no gamma values.  In
+any case, the meanings of those parameters is the same as the more
+modern \fB-gamma\fP, \fB-rgamma\fP, \fB-ggamma\fP, and
+\fB-bgamma\fP options described below.
+
+
+.UN options
+.SH OPTIONS
+.PP
+In addition to the options common to all programs based on libnetpbm
+(most notably \fB-quiet\fP, see 
+.UR index.html#commonoptions
+ Common Options
+.UE
+\&), \fBpnmgamma\fP recognizes the following
+command line options:
+
+
+
+.TP
+\fB-bt709tolinear\fP
+Convert the image from BT.709 luminance to radiance.  I.e. convert
+from true PPM or PGM to a radiance-linear variation that can be used
+with certain tools that need it.
+.sp
+This option was new in Netpbm 10.32 (February 2006).
+
+.TP
+\fB-lineartobt709\fP
+Convert the image from radiance to BT.709 luminance.  I.e. convert
+to true PPM or PGM from a radiance-linear variation.
+.sp
+You get true BT.709 (ergo true PPM or PGM) only if you use the
+default gamma value (i.e. don't specify \fB-gamma\fP, etc.).
+.sp
+This option was new in Netpbm 10.32 (February 2006).
+
+.TP
+\fB-bt709tosrgb\fP
+Convert the image from BT.709 luminance to SRGB luminance.
+I.e. convert from true PPM or PGM to an SRGB-based variation that is
+required by certain tools and display devices.
+.sp
+You get true SRGB only if you use the default gamma value
+(i.e. don't specify \fB-gamma\fP, etc.).
+.sp
+This option was new in Netpbm 10.32 (February 2006).
+
+.TP
+\fB-srgbtobt709\fP
+Convert the image from SRGB luminance to BT.709 luminance.
+I.e. convert to true PPM or PGM from an SRGB-based variation.
+.sp
+This option was new in Netpbm 10.32 (February 2006).
+
+.TP
+\fB-bt709ramp\fP
+Same as \fB-lineartobt709\fP, but using the old syntax.
+.sp
+This option was renamed in Netpbm 10.32 (February 2006).  Before that,
+its name is \fB-cieramp\fP.
+
+.TP
+\fB-cieramp\fP
+This is an obsolete synonym for \fB-bt709ramp\fP.
+.sp
+The name of this option comes from a former belief that this was a
+standard of CIE (International Commission On Illumination), but it now
+(August 2005) looks like it never was.
+
+.TP
+\fB-srgbramp \fP
+Convert the image from radiance to SRGB luminance.  Note that it is
+true SRGB only if you use the default gamma value (i.e. don't specify
+any gamma parameters).
+.sp
+This is an old syntax option.  There is no equivalent in the new
+syntax because it really shouldn't be a function of \fBpnmgamma\fP at
+all.  It exists solely for backward compatibility.  The reason it
+shouldn't exist is that the way to do this conversion consistent with
+the Netpbm philosophy is do a \fB-lineartobt709\fP followed by a
+\fB-bt709tosrgb\fP.  It's exactly analogous to the way you have to
+convert from PNG to TIFF by doing a \fBpngtopam\fP followed by a
+\fBpnmtotiff\fP.  The \fB-srgbramp\fP option actually dates to
+before there was a standard definition of what the sample values of a
+Netpbm image measure, and \fBpnmgamma\fP considered radiance-linear
+to be the proper intermediate format.
+
+.TP
+\fB-ungamma\fP
+Apply the inverse of the specified transfer function (i.e. go from
+gamma-adjusted luminance to radiance).
+.sp
+This is valid only with \fB-bt709ramp\fP (aka \fB-cieramp\fP),
+\fB-srgbramp\fP, and the default exponential transfer function.
+
+.TP
+\fB-gamma=\fP\fIfloat\fP
+This specifies the gamma value to use in the transfer function.  All
+of the transfer functions involve an exponent, and the gamma value is that
+exponent.
+.sp
+The standards specify a particular gamma value.  If you use anything
+else, you are varying from the standard.
+.sp
+The default is the standard value.  For the simple exponential transfer
+function (which is not a standard), the default is 2.2.
+.sp
+In the \fB-bt709tosrgb\fP and \fB-srgbtobt709\fP conversions
+there are \fItwo\fP exponents.  \fB-gamma\fP affects the
+"to" function; the "from" function always uses the
+standard gamma value.
+.sp
+If you specify one of the component-specific options (\fB-rgamma\fP,
+etc.), that overrides the \fB-gamma\fP value.
+.sp
+With the \fB-bt709ramp\fP (aka \fB-cieramp\fP), \fB-srgbramp\fP,
+or the default exponential transfer function, you can't actually use
+this option, but you specify the same thing with 
+.UR #parameters
+parameters.
+.UE
+\&
+.sp
+This option was new in Netpbm 10.32 (February 2006).
+
+.TP
+\fB-rgamma=\fP\fIfloat\fP
+.TP
+\fB-ggamma=\fP\fIfloat\fP
+.TP
+\fB-bgamma=\fP\fIfloat\fP
+These options are just like \fB-gamma\fP, except they specify the
+value for a particular one of the color components.
+.sp
+If you don't specify this option for a particular color component,
+the default is the \fB-gamma\fP value (or \fB-gamma\fP's default if
+you didn't specify that either).
+.sp
+With the \fB-bt709ramp\fP (aka \fB-cieramp\fP), \fB-srgbramp\fP,
+or the default exponential transfer function, you can't actually use
+this option, but you specify the same thing with 
+.UR #parameters
+parameters.
+.UE
+\&
+.sp
+This option was new in Netpbm 10.32 (February 2006).
+
+.TP
+\fB-maxval=\fP\fImaxval\fP
+This is the maxval of the output image.  By default, the maxval of
+the output is the same as that of the input.
+.sp
+Because the transformation is not linear, you need a greater maxval
+in the output in order not to lose any information from the input.
+For example, if you convert to radiance-linear sample values with 
+\f(CW-ungamma -bt709ramp\fP and default gamma value, and your maxval is
+255 on both input and output, 3 different input sample values all
+generate output sample value 254.  In order to have a different output
+sample value for each input sample value, you would need an output
+maxval at least 3 times the input maxval.
+.sp
+This option was new in Netpbm 10.32 (February 2006).  Before that,
+you can achieve the same result by increasing the maxval of the input
+or decreasing the maxval of the output using \fBpamdepth\fP.
+
+
+
+.UN gamma
+.SH WHAT IS GAMMA?
+.PP
+A good explanation of gamma is in Charles Poynton's Gamma FAQ at
+.BR "
+http://www.poynton.com/GammaFAQ.html" (1)\c
+\& and Color FAQ at
+.BR "
+http://www.poynton.com/ColorFAQ.html" (1)\c
+\&.
+.PP
+In brief: The simplest way to code an image is by using sample
+values that are directly proportional to the radiance of the color
+components.  Radiance is a physical quantification based on the amount
+of power in the light; it is easily measurable in a laboratory, but
+does not take into account what the light looks like to a person.  It
+wastes the sample space because the human eye can't discern
+differences between low-radiance colors as well as it can between
+high-radiance colors.  So instead, we pass the radiance values
+through a transfer function that makes it so that changing a sample
+value by 1 causes the same level of perceived color change anywhere in
+the sample range.  We store those resulting values in the image file.
+That transfer function is called the gamma transfer function and the
+transformation is called gamma adjusting.
+.PP
+The gamma-adjusted value, proportional to subjective brightness,
+are known as the luminance of the pixel.
+.PP
+There is no precise objective way to measure luminance, since it's
+psychological.  Also, perception of brightness varies according to a
+variety of factors, including the surrounding in which an image is
+viewed.  Therefore, there is not just one gamma transfer function.
+.PP
+Virtually all image formats, either specified or de facto, use
+gamma-adjusted values for their sample values.
+.PP
+What's really nice about gamma is that by coincidence, the inverse
+function that you have to do to convert the gamma-adjusted values
+back to radiance is done automatically by CRTs.  You just apply a
+voltage to the CRT's electron gun that is proportional to the
+gamma-adjusted sample value, and the radiance of the light that comes
+out of the screen is close to the radiance value you had before you
+applied the gamma transfer function!
+.PP
+And when you consider that computer video devices usually want you
+to store in video memory a value proportional to the signal voltage
+you want to go to the monitor, which the monitor turns into a
+proportional drive voltage on the electron gun, it is really
+convenient to work with gamma-adjusted sample values.
+
+.UN seealso
+.SH SEE ALSO
+.BR "pnm" (1)\c
+\&
+
+.UN author
+.SH AUTHOR
+
+Copyright (C) 1991 by Bill Davidson and Jef Poskanzer.
+.SH DOCUMENT SOURCE
+This manual page was generated by the Netpbm tool 'makeman' from HTML
+source.  The master documentation is at
+.IP
+.B http://netpbm.sourceforge.net/doc/pnmgamma.html
+.PP
\ No newline at end of file