SGI2PS(1) Impressario SGI2PS(1)NAMEsgi2ps - convert an SGI image file to PostScript
SYNOPSISsgi2ps [-O filename] [-L filename] [-B]
[-C colorspace] [-F] [-f] [-r angle]
[-p imageRes] [-z factor] [-n nCopies]
[-G g0[,g1,g2]] [-N nUpX[,nUpY]]
[-I filename] [-c filename] [-h] [-D]
[SGIImageFilename ...]
DESCRIPTIONsgi2ps converts raster files in SGI image format into PostScript code.
The program provides a number of image transformation capabilities
including zooming, rotation and gamma correction. In addition, sgi2ps
provides the capability to display multiple images on a single physical
page.
Command Line Options
Typically, sgi2ps expects at least one SGI image file to be specified as
input on the command line after all option switches. If no image file is
specified on the command line, sgi2ps will read from the standard input.
By default, sgi2ps assumes that its output should be written to the
standard output and messages should be written to standard error.
-O filename
Specifies the name of the file to which the PostScript output
will be sent. If the -O option is not specified, output will
be sent to the standard output.
-L filename
Specifies the name of the file to which error, warning and
informational messages are to be written. If the file specified
already exists, any messages generated by sgi2ps will be
appended to the end of the file. If the -L option is not
specified, message output will be sent to standard error.
-B Specifies that binary PostScript should be output where
applicable. The majority of the output from sgi2ps is bitmap
image data. By default this data is output as ASCII hexadecimal
values. Specifying -B will output this image data as binary
values thereby cutting in half the number of bytes of
PostScript data output. However, binary data output should only
be used when the communications channel between sgi2ps and the
PostScript interpreter can accept 8-bit data. This precludes
the use of the -B switch when transmitting output over serial
connections.
-C colorspace
Specifies the output data colorspace. The value of colorspace
may be one of the following: w (black and white), the default,
cmyk, or rgb. The PostScript produced by cmyk and rgb can only
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be interpreted by a Level 2 PostScript interpreter or a Level 1
interpreter with the CMYK color extensions (e.g. psrip(1)). The
PostScript produced by w can be sent to any Level 1
interpreter. The colorspace conversion equations used by sgi2ps
are:
W to RGB: r = g = b = w
W to CMYK: c = m = y = 0; k = 1 - w
RGB to W: w = 0.299 r + 0.587 g + 0.114 b
RGB to CMYK:
ci = 1 - r; mi = 1 - g; yi = 1 - b
k = min(ci, mi, yi)
c = ci - k; m = mi - k: y = yi - k
-F Specifies that the image should be oriented so that it best
fits the page. That is, the image is oriented such that its
longer dimension is parallel with the longer dimension of the
paper. If -F is specified, any rotation specified by the -r
switch is ignored. By default the image is oriented with zero
degrees of rotation unless the -r switch specifies a different
rotation.
-f Specifies that the output image should be flipped (mirrored)
about the vertical axis. This flag is useful when creating
transparencies. Note that flipping of the image is performed
after any rotation. Therefore, the image is always flipped
about the vertical axis.
-r angle Specifies that the image is to be rotated by angle degrees.
angle may be any positive or negative integer value. Positive
rotations are counter-clockwise measured from the horizontal
axis. The default rotation angle is 0. Note that rotation is
performed before any image flipping (-f). The -r switch is
ignored if the best-fit switch -F is specified.
-z factor and -p imageRes
Each of these switches provides scaling of the original image.
The two switches are mutually exclusive.
The -z switch provides image zooming. factor is a positive
floating point value typically between 0.0 and 1.0. A zoom
factor of 1.0, the default, indicates that the image should be
scaled to fit the entire page while preserving the original
image's aspect ratio. A zoom factor of 0.5 would produce an
image sized to 50% of that needed to fit the entire page. A
zoom factor of 0.0 produces no zooming. Instead the image is
output at its original size.
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If an image must be sized based on a given resolution, the -p
switch should be specified in place of the -z switch. The
imageRes argument specifies the resolution used to size the
image in dots per inch. This resolution is independent of the
output device resolution. For example, suppose an image is one
inch by one inch when displayed on a 96 dpi monitor. In order
to print that image on a 300 dpi printer so that it remains one
inch by one inch the -p switch would be specified with an
imageRes of 96.
-n nCopies
Specifies the number of copies to produce of each page.
Specifying this switch simply sets the value of the #copies
variable in the output PostScript code. The value of this
variable is used by the PostScript operator showpage to
determine the number of output copies to produce. By default
the #copies variable is not specified and the number of copies
then defaults to one.
-G g0[,g1,g2]
This switch provides gamma correction of the input image data.
The gamma function is:
corrected value = value ^ gamma
The gamma value (g0, etc.) is typically a value between 0.0 and
3.0. A gamma value less than 1.0 will tend to lighten the image
while a value greater than 1.0 will tend to darken the image. A
gamma of 1.0 will leave the image data unchanged. The gamma
value may be specified for each input color channel
individually or as a group. If g0 is the only gamma value
specified, this value will be applied to all output channels.
Note that a black and white image contains one input color
channel, and an RGB image contains three input channels. The
default gamma value is 1.0 for all channels.
-N nUpX[,nUpY]
sgi2ps allows multiple SGI image files to be specified on the
command line. By default, each image is output on a separate
physical page. The -N switch provides the capability to divide
up one physical page into multiple virtual pages. This is often
called n-up display. Using n-up, multiple image files can be
displayed on the same physical page. If only the nUpX value is
specified the physical page will be divided into nUpX by nUpX
virtual pages. If both nUpX and nUpY are specified, the
physical page will be divided into nUpX by nUpY virtual pages.
Images are displayed in row (horizontal) major order. Note
that nUpX is measured along the horizontal, x, axis. For an 8.5
by 11.0 inch page, the horizontal axis is the short dimension
in portrait mode and the long dimension in landscape mode.
Rotation is performed on each image individually and best-fit
orientation is determined for each image individually. Zooming
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is relative to the virtual page size. Note that image
replication is not performed. The number of images specified on
the command line is the number of images displayed in the
virtual pages.
-I filename
sgi2ps places a PostScript code prolog at the start of the
output file. By default, this prolog code is read from the
file /usr/lib/print/data/PSImageProlog. The -I switch allows a
different prolog file to be specified. This switch is not
intended for general use.
-c filename
The most common form of SGI Image file is the so called Normal
image. This image contains the actual intensity values for each
image channel at each pixel location. Another form of SGI
Image file is the so called Screen image. This image consists
of a single value at each pixel. The value is an index into a
colormap that contains the actual pixel intensity values for
each channel. This type of image is also referred to as a
colormap image. In order to process a colormap image, the
colormap that corresponds to the image must be specified. By
default sgi2ps obtains its colormap from the file
SGIDefColormap.map. This file contains the default SGI system
colormap. The -c option can be used to specify a different
colormap file. A colormap file can be created using the
makemap(1G) and savemap(1G) programs. This switch is not
intended for general use.
-h Prints a program usage message to the standard error. This
usage message also lists the currently supported output
configurations.
-D Specifies verbose output for debugging purposes.
NOTES
1. The PostScript output produced by sgi2ps conforms to the Adobe
PostScript Document Structuring Conventions Version 3.0 as specified
in Appendix G of the "PostScript Language Reference Manual", 2nd
edition.
2. The sgi2ps program supersedes the rgb2ps program. The rgb2ps program
should not be used for new development and may be removed from
future releases.
3. The PostScript output produced by sgi2ps primarily wraps the input
bitmap image data with PostScript instructions. Therefore, the
amount of output data can be quit large especially if multiple image
files are specified or if the images are large. The size of the
output file should be kept in mind when sending the PostScript
output over a slow communications channel such as a serial line.
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4. If sgi2ps is given an unrecognized or incomplete command line option
switch, it will print a warning message to the standard error,
ignore the option and continue processing.
5. If an image file is specified on the command line, sgi2ps will not
read its stdin for images.
6. Processing an SGI Image format file requires random seeking within
the file. Therefore, when sgi2ps is obtaining its input image from
a pipe to standard input, a disk based copy of the input image must
be created. This temporary image file will be created in the
directory specified by the TMPDIR environment variable. If that
variable is not set, the temporary file will be created in /var/tmp.
There must be sufficient free space in the temporary file directory
to store a complete copy of the image file or sgi2ps will fail.
7. sgi2ps can only process a single image file when reading from
standard input.
8. Previous versions of sgi2ps performed gamma correction on the output
data. Starting with Impressario 1.2, sgi2ps performs gamma
correction on the input image data.
9. sgi2ps can process Normal and Screen format SGI Image files. Images
in the obsolete Dither format must be converted to Normal format
images using the fromdi(6D) program.
FILES
/usr/lib/print/sgi2ps Program file
/usr/lib/print/data/PSImageProlog PostScript prolog file
/usr/lib/print/data/SGIDefColormap.map Default colormap file
TRADEMARKS
PostScript is a registered trademark of Adobe Systems, Inc.
SEE ALSOpsrip(1), stiff2ps(1), PostScript Language Reference Manual - 2nd ed.,
Adobe Systems, Inc., makemap(1G), savemap(1G), fromdi(6D)
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