harvey/sys/man/1/jpg

.TH JPG 1
.SH NAME
jpg, gif, png, ppm, togif, toppm, topng \- view and convert pictures
.SH SYNOPSIS
.B jpg
[
.B -39cdefFkJrtv
] [
.I file ...
]
.PP
.B gif
[
.B -39cdektv
] [
.I file ...
]
.PP
.B png
[
.B -39cdektv
] [
.I file ...
]
.B ppm
[
.B -39cdektv
] [
.I file ...
]
.PP
.B togif
[
.B -c
.I comment
] [
.B -l
.I loopcount
] [
.B -d
.I msec
] [
.B -t
.I transindex
] [
.I file ...
[
.B -d
.I msec
]
.I file ...
]
.PP
.B toppm
[
.B -c
.I comment
] [
.I file
]
.PP
.B topng
[
.B -c
.I comment
] [
[
.B -g
.I gamma
] [
.I file
]
.SH DESCRIPTION
These programs read, display, and write image files in public formats.
.IR Jpg ,
.IR gif ,
.IR png ,
and
.I ppm
read files in the corresponding formats and, by default, display
them in the current window; options cause them instead to convert the images
to Plan 9 image format and write them to standard output.
.IR Togif ,
.IR Toppm ,
and
.I topng
read Plan 9 images files, convert them to GIF, PPM, or PNG, and write them to standard output.
.PP
The default behavior of
.IR jpg ,
.IR gif ,
and
.IR ppm
is to display the
.IR file ,
or standard input if no file is named.
Once a file is displayed, typing a character causes the program to display the next image.
Typing a
.BR q ,
DEL, or control-D exits the program.
For a more user-friendly interface, use
.IR page (1),
which invokes these programs to convert the images to standard format,
displays them, and offers scrolling, panning, and menu-driven navigation among the files.
.PP
These programs share many options:
.TP
.B -e
Disable Floyd-Steinberg error diffusion, which is used to improve the appearance
of images on color-mapped displays, typically with 8 bits per pixel.
Primarily useful for debugging; if the display has true RGB color, the image
will be displayed in full glory.
.TP
.B -k
Convert and display the image as a black and white (really grey-scale) image.
.TP
.B -v
Convert the image to an RGBV color-mapped image, even if the
display has true RGB color.
.TP
.B -d
Suppress display of the image; this is set automatically by
any of the following options:
.TP
.B -c
Convert the image to a Plan 9 representation, as defined by
.IR image (6),
and write it to standard output.
.TP
.B -9
Like
.BR -c ,
but produce an uncompressed image.
This saves processing time, particularly when the output is
being piped to another program such as
.IR page (1),
since it avoids compression and decompression.
.TP
.B -t
Convert the image, if it is in color, to a true color RGB image.
.TP
.B -3
Like
.BR -t ,
but force the image to RGB even if it is originally grey-scale.
.PD
.PP
.PP
The
.IR togif
and
.IR toppm
programs go the other way: they convert from Plan 9 images to GIF and PPM,
and have no display capability.
Both accept an option
.B -c
to set the comment field of the resulting file.
If there is only one input picture,
.I togif
converts the image to GIF format.
If there are many
.IR files ,
though, it will assemble them into an animated GIF file.
The options control this process:
.TP
.BI -l loopcount
By default, the animation will loop forever;
.I loopcount
specifies how many times to loop.
A value of zero means loop forever and a negative value means
to stop after playing the sequence once.
.TP
.BI -d msec
By default, the images are displayed as fast as they can be rendered.
This option specifies the time, in milliseconds, to pause while
displaying the next named
.IR file .
.PD
.PP
.I Gif
translates files that contain a `transparency' index by attaching
an alpha channel to the converted image.
.SH SOURCE
.B /sys/src/cmd/jpg
.SH "SEE ALSO"
.IR page (1),
.IR image (6).
.SH BUGS
Writing an animated GIF using
.I togif
is a clumsy undertaking.