DISPLAY(1) X Version 11(1 July 1991) DISPLAY(1)
NAME
display - display an image on any workstation running X
SYNOPSIS
display [ options ...] file [ [ options ...] file ...]
DESCRIPTION
Display is a machine architecture independent image processing and
display program. It can display any image in the MIFF format on any
workstation display running an X server. Display first determines the
hardware capabilities of the workstation. If the number of unique colors
in the image is less than or equal to the number the workstation can
support, the image is displayed in an X window. Otherwise the number of
colors in the image is first reduced to match the color resolution of the
workstation before it is displayed.
This means that a continuous-tone 24 bits/pixel image can display on a 8
bit pseudo-color device or monochrome device. In most instances the
reduced color image closely resembles the original. Alternatively, a
monochrome or pseudo-color image can display on a continuous-tone 24
bits/pixels device.
EXAMPLES
To scale an image of a cockatoo to exactly 640 pixels in width and 480
pixels in height and position the window at location (200,200), use:
display -geometry 640x480+200+200 cockatoo.miff
To display an image of a cockatoo without a border centered on a
backdrop, use:
display -backdrop -borderwidth 0 cockatoo.miff
To tile an image of a cockatoo onto the root window, use:
display -window root cockatoo.miff
OPTIONS
-backdrop
display the image centered on a backdrop.
This backdrop covers the entire workstation screen and is useful for
hiding other X window activity while viewing the image. The color
of the backdrop is specified as the background color. Refer to X
RESOURCES for details.
-clip <width>x<height>{+-}<x offset>{+-}<y offset>
preferred size and location of the clipped image. See X(1) for
details about the geometry specification.
Use clipping to apply image processing options, or display, only a
particular area of an image.
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The equivalent X resource for this option is clipGeometry (class
ClipGeometry). See X RESOURCES for details.
-colors value
preferred number of colors in the image.
The actual number of colors in the image may be less than your
request, but never more. Note, this is a color reduction option.
Images with less unique colors than specified with this option will
remain unchanged. Refer to COLOR REDUCTION ALGORITHM for more
details.
Note, options -dither and -treedepth affect the color reduction
algorithm.
-compress type
the type of image compression: QEncoded or RunlengthEncoded.
Use this option with -write to specify the the type of image
compression. See MIFF FILE FORMAT for details.
Specify +compress to store the binary image in an uncompressed
format. The default is the compression type of the specified image
file.
-delay seconds
display the next image after pausing.
This option is useful when viewing several images in sequence. Each
image will display and wait the number of seconds specified before
the next image is displayed. The default is to display the image
continuously until you terminate it.
-display host:display[.screen]
specifies the X server to contact; see X(1).
-dither
apply Floyd/Steinberg error diffusion to the image.
The basic strategy of dithering is to trade intensity resolution for
spatial resolution by averaging the intensities of several
neighboring pixels. Images which suffer from severe contouring when
reducing colors can be improved with this option.
The -colors, -gray, or -monochrome option is required for this
option to take effect.
-enhance
apply a digital filter to enhance a noisy image.
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-gamma value
level of gamma correction.
The same color image displayed on two different workstations may
look different due to differences in the display monitor. Use gamma
correction to adjust for this color difference. Reasonable values
extend from 0.8 to 2.3.
-geometry <width>x<height>{+-}<x offset>{+-}<y offset>
preferred size and location of the image window. See X(1) for
details about the geometry specification. By default, the window
size is the image size and the location is choosen by you when it is
mapped.
If the specified image size is smaller than the actual image size,
the image is first reduced to an integral of the specified image
size with an antialias digital filter. The image is then scaled to
the exact specified image size with pixel replication. If the
specified image size is greater than the actual image size, the
image is first enlarged to an integral of the specified image size
with bilinear interpolation. The image is then scaled to the exact
specified image size with pixel replication.
When displaying an image on an X server, the x and y offset in the
geometry specification is relative to the root window. When
printing an image, the x and y offset in the geometry specification
is relative to a Postscript page. See -print for more details.
The equivalent X resource for this option is imageGeometry (class
ImageGeometry). See X RESOURCES for details.
-gray
transform the image to gray scale colors.
-inverse
apply color inversion to image.
The red, green, and blue intensities of an image are negated.
-magnify value
specifies an integral factor by which the image should be enlarged.
The default is 2.
This value only affects the magnification window which is invoked
with button number 1 after the image is displayed. Refer to BUTTONS
for more details.
-map type
display image using this Standard Colormap type.
Choose from these Standard Colormap types:
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default
best
red
green
blue
gray
The X server must support the Standard Colormap you choose,
otherwise an error occurs. See xcmap(1) for one way of creating
Standard Colormaps.
-monochrome
transform the image to black and white.
Monochrome images can benefit from error diffusion. Use -dither
with this option to diffuse the error.
-noise
reduce the noise in an image with a noise peak elimination filter.
The principal function of noise peak elimination filter is to smooth
the objects within an image without losing edge information and
without creating undesired structures. The central idea of the
algorithm is to replace a pixel with its next neighbor in value
within a 3 x 3 window, if this pixel has been found to be noise. A
pixel is defined as noise if and only if this pixel is a maximum or
minimum within the 3 x 3 window.
-normalize
tranform image to span the full range of color values.
-print file
write image as encapsulated Postscript to a file.
You can view the file with any Postscript compatible viewer or
printer. The image is displayed as color on viewers and printers
that support color Postscript, otherwise it is displayed as
grayscale.
If file already exists, you will be prompted as to whether it should
be overwritten.
By default, the image is scaled and centered to fit on an 612x792
point Postscript page. To specify a specific image size or a
particular location on the Postscript page, use -geometry.
By default the image is output in portrait mode. Use -rotate 90 to
display the image in landscape mode.
The equivalent X resource for this option is printFilename (class
PrintFilename). See X RESOURCES for details.
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-reflect
create a "mirror image" by reflecting the image scanlines.
-rotate degrees
apply Paeth image rotation to the image.
-scale <width factor>x<height factor>
preferred size factors of the image.
This option behaves like -geometry except the width and height
values are relative instead of absolute. The image size is
multiplied by the width and height factors to obtain the final image
dimensions. If only one factor is specified, both the width and
height factors assume the value.
Factors may be fractional. For example, a factor of 1.5 will
increase the image size by one and one-half.
The equivalent X resource for this option is scaleGeometry (class
ScaleGeometry). See X RESOURCES for details.
-scene number
image scene number.
-treedepth value
Normally, this integer value is zero or one. A zero or one tells
Display to choose a optimal tree depth for the color reduction
algorithm.
An optimal depth generally allows the best representation of the
source image with the fastest computational speed and the least
amount of memory. However, the default depth is inappropriate for
some images. To assure the best representation, try values between
2 and 8 for this parameter. Refer to COLOR REDUCTION ALGORITHM for
more details.
The -colors, -gray, or -monochrome option is required for this
option to take effect.
-verbose
print detailed information about the image.
This information is printed: image scene number; image name; image
size; the image class (DirectClass or PseudoClass); the total number
of unique colors (if known); and the number of seconds to read and
transform the image. Refer to MIFF FILE FORMAT for a description of
the image class.
If -colors is also specified, the total unique colors in the image
and color reduction error values are printed. Refer to MEASURING
COLOR REDUCTION ERROR for a description of these values.
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-visual type
display image using this visual type.
Choose from these visual classes:
StaticGray
GrayScale
StaticColor
PseudoColor
TrueColor
DirectColor
default
visual id
The X server must support the visual you choose, otherwise an error
occurs. If a visual is not specified, the visual class that can
display the most simultaneous colors on the default screen is
choosen.
-window id
set the background pixmap of this window to the image.
d can be a window id or name. Specify 'root' to select X's root
window as the target window.
By default the image is tiled onto the background of the target
window. If -backdrop or -geometry are specified, the image is
surrounded by the background color. Refer to X RESOURCES for
details.
The image will not display on the root window if the image has more
unique colors than the target window colormap allows. Use -colors
to reduce the number of colors.
-write file
write image to a file.
The image is stored in the MIFF image format. If the number of
unique colors in the image exceed 65535, it is stored as
DirectClass; otherwise, it is stored as PseudoClass format. Refer
to MIFF FILE FORMAT for more details.
Use -compress to specify the type of image compression.
If file has the extension .Z, the file size is reduced using
Lempel-Ziv coding with compress. If file already exists, you will
be prompted as to whether it should be overwritten.
The equivalent X resource for this option is writeFilename (class
WriteFilename). See X RESOURCES for details.
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In addition to those listed above, you can specify these standard X
resources as command line options: -background, -bordercolor,
-borderwidth, -font, -foreground, -iconGeometry, -iconic, -name, or
-title. See X RESOURCES for details.
Any option you specify on the command line remains in effect until it is
explicitly changed by specifying the option again with a different
effect. For example, to display two images, the first with 32 colors and
the second with only 16 colors, use:
display -colors 32 cockatoo.miff -colors 16 macaw.miff
Change - to + in any option above to reverse its effect. For example,
specify +display to apply image transformations without viewing them on
the X server. Or, specify +compress to store the binary image in an
uncompressed format.
Specify file as - for standard input or output. If file has the
extension .Z, the file is decoded with uncompress.
BUTTONS
Control-1
Press and drag to pan the image.
1 Press and drag to select a command from a pop-up menu. Choose from
these commands:
Image Info
Write Image
Print Image
Annotate Image
Reflect Image
Rotate Right
Rotate Left
Half Size
Double Size
Restore Image
Next Image
Quit
2 Press and drag to define a region of the image to clip. Release the
button to crop the image, or return the pointer to the location of
the initial button press to cancel the cropping operation.
3 Press and drag to define a region of the image to magnify.
KEYS
i Press to display information about the image. Press any key or
button to erase the information.
This information is printed: image name; image size; the visual
class (see -visual); and the total number of unique colors in the
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image.
w Press to write the image to a file.
p Press to print the image to a file.
a Press to annotate the image with text.
Refer to IMAGE ANNOTATION for more details.
r Press to reflect the image scanlines.
/ Press to rotate the image 90 degrees clockwise.
\ Press to rotate the image 90 degrees counter-clockwise.
< Press to half the image size.
> Press to double the image size.
o Press to restore the image to its original size.
n Press to display the next image.
q Press to discard all images and exit program.
1-9 Press to change the level of magnification.
X RESOURCES
Display options can appear on the command line or in your X resource
file. Options on the command line supercede values specified in your X
resource file. See X(1) for more information on X resources.
All display options have a corresponding X resource. In addition, the
display program uses the following X resources:
background (class Background)
Specifies the preferred color to use for the image window
background. The default is black.
borderColor (class BorderColor)
Specifies the preferred color to use for the image window border.
The default is white.
borderWidth (class BorderWidth)
Specifies the width in pixels of the image window border. The
default is 2.
font (class Font)
Specifies the name of the preferred font to use when displaying text
within the image window. The default is 9x15, fixed, or 5x8
determined by the image window size.
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font[1-9] (class Font[1-9])
Specifies the name of the preferred font to use when annotating the
image window with text. The default fonts are fixed, variable, 5x8,
6x10, 7x13bold, 8x13bold, 9x15bold, 10x20, and 12x24. Refer to IMAGE
ANNOTATION for more details.
foreground (class Foreground)
Specifies the preferred color to use for text within the image
window. The default is white.
iconGeometry (class IconGeometry)
Specifies the preferred size and position of the application when
iconified. It is not necessarily obeyed by all window managers.
iconic (class Iconic)
This resource indicates that you would prefer that the application's
windows initially not be visible as if the windows had be
immediately iconified by you. Window managers may choose not to
honor the application's request.
name (class Name)
This resource specifies the name under which resources for the
application should be found. This resource is useful in shell
aliases to distinguish between invocations of an application,
without resorting to creating links to alter the executable file
name. The default is the application name.
pen[1-9] (class Pen[1-9])
Specifies the color of the preferred font to use when annotating the
image window with text. The default colors are black, blue, green,
cyan, gray, red, magenta, yellow, and white. Refer to IMAGE
ANNOTATION for more details.
title (class Title)
This resource specifies the title to be used for the image window.
This information is sometimes used by a window manager to provide
some sort of header identifying the window. The default is the
image file name.
IMAGE ANNOTATION
An image is annotated with text interactively. There is no command line
argument to annotate an image. To begin, press button 1 and choose
Annotate Image from the command menu (see BUTTONS). Alternatively, press
a in the image window (see KEYS). The cursor will change to a pencil to
indicate you are in image annotation mode. To exit immediately, press
button 1 followed by ESC.
In image annotation mode, a button press has a different effect than
described in BUTTONS. Press a button to affect this behavior:
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1 Press to select a location within the image window to begin entering
text.
2 Press and drag to select a font from a pop-up menu. Choose from
these fonts:
fixed
variable
5x8
6x10
7x13bold
8x13bold
9x15bold
10x20
12x24
Other fonts can be specified by setting the X resources font1
through font9. Refer to X RESOURCES for more details.
3 Press and drag to select a font color from a pop-up menu. Choose
from these font colors:
black
blue
cyan
green
gray
red
magenta
yellow
white
Other font colors can be specified by setting the X resources pen1
through pen9. Refer to X RESOURCES for more details.
Choosing a font and its color is optional. The default font is fixed and
the default color is black. However, you must choose a location to begin
entering text and press button 1. An underscore character will appear at
the location of the cursor where button 1 was pressed. The underscore
indicates you are in text entering mode. To exit immediately, press ESC.
In text entering mode, any key presses will display the character at the
location of the underscore and advance the underscore cursor. Enter your
text and once completed press ESC to finish your image annotation. To
correct errors press BACK SPACE. To delete an entire line of text, press
DELETE. Any text that exceeds the boundaries of the image window is
automatically continued onto the next line.
Before exiting image annotation mode, immediately after pressing the ESC
key, the image is permanently updated with the text you entered. There
is no way to `undo' your changes so be careful to check your text before
you press ESC.
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The actual color you request for the font is saved in the image.
However, the color that appears in your image window may be different.
For example, on a monochrome screen the text will appear black or white
even if you choose the color red as the font color. However, the image
saved to a file with -write will be written with red lettering. To
assure the correct color text in the final image, any PseudoClass image
is promoted to DirectClass (see MIFF FILE FORMAT). To force a
PseudoClass image to remain PseudoClass, use -colors.
COLOR REDUCTION ALGORITHM
This section describes how Display performs color reduction in an image.
To fully understand this section, you should have a knowledge of basic
imaging techniques and the tree data structure and terminology.
For purposes of color allocation, an image is a set of n pixels, where
each pixel is a point in RGB space. RGB space is a 3-dimensional vector
space, and each pixel, pi, is defined by an ordered triple of red,
green, and blue coordinates, (ri, gi, bi).
Each primary color component (red, green, or blue) represents an
intensity which varies linearly from 0 to a maximum value, cmax, which
corresponds to full saturation of that color. Color allocation is
defined over a domain consisting of the cube in RGB space with opposite
vertices at (0,0,0) and (cmax,cmax,cmax). Display requires cmax = 255.
The algorithm maps this domain onto a tree in which each node represents
a cube within that domain. In the following discussion, these cubes are
defined by the coordinate of two opposite vertices: The vertex nearest
the origin in RGB space and the vertex farthest from the origin.
The tree's root node represents the the entire domain, (0,0,0) through
(cmax,cmax,cmax). Each lower level in the tree is generated by
subdividing one node's cube into eight smaller cubes of equal size. This
corresponds to bisecting the parent cube with planes passing through the
midpoints of each edge.
The basic algorithm operates in three phases: Classification, Reduction,
and Assignment. Classification builds a color description tree for the
image. Reduction collapses the tree until the number it represents, at
most, is the number of colors desired in the output image. Assignment
defines the output image's color map and sets each pixel's color by
reclassification in the reduced tree.
Classification begins by initializing a color description tree of
sufficient depth to represent each possible input color in a leaf.
However, it is impractical to generate a fully-formed color description
tree in the classification phase for realistic values of cmax. If color
components in the input image are quantized to k-bit precision, so that
cmax = 2k-1, the tree would need k levels below the root node to allow
representing each possible input color in a leaf. This becomes
prohibitive because the tree's total number of nodes is
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≳ k
i=1 8k
A complete tree would require 19,173,961 nodes for k = 8, cmax = 255.
Therefore, to avoid building a fully populated tree, Display: (1)
Initializes data structures for nodes only as they are needed; (2)
Chooses a maximum depth for the tree as a function of the desired number
of colors in the output image (currently log4(colormap size)+2). A tree
of this depth generally allows the best representation of the source
image with the fastest computational speed and the least amount of
memory. However, the default depth is inappropriate for some images.
Therefore, the caller can request a specific tree depth.
For each pixel in the input image, classification scans downward from the
root of the color description tree. At each level of the tree, it
identifies the single node which represents a cube in RGB space
containing the pixel's color. It updates the following data for each
such node:
n1: Number of pixels whose color is contained in the RGB cube which this
node represents;
n2: Number of pixels whose color is not represented in a node at lower
depth in the tree; initially, n2 = 0 for all nodes except leaves
of the tree.
Sr, Sg, Sb:
Sums of the red, green, and blue component values for all pixels not
classified at a lower depth. The combination of these sums and n2
will ultimately characterize the mean color of a set of pixels
represented by this node.
Reduction repeatedly prunes the tree until the number of nodes with n2 >
0 is less than or equal to the maximum number of colors allowed in the
output image. On any given iteration over the tree, it selects those
nodes whose n1 count is minimal for pruning and merges their color
statistics upward. It uses a pruning threshold, np, to govern node
selection as follows:
np = 0
while number of nodes with (n2 > 0) > required maximum number of colors
prune all nodes such that n1 <= np
Set np to minimum n1 in remaining nodes
When a node to be pruned has offspring, the pruning procedure invokes
itself recursively in order to prune the tree from the leaves upward.
The values of n2 Sr, Sg, and Sb in a node being pruned are always added
to the corresponding data in that node's parent. This retains the pruned
node's color characteristics for later averaging.
For each node, n2 pixels exist for which that node represents the
smallest volume in RGB space containing those pixel's colors. When n2 >
0 the node will uniquely define a color in the output image. At the
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beginning of reduction, n2 = 0 for all nodes except the leaves of the
tree which represent colors present in the input image.
The other pixel count, n1, indicates the total number of colors within
the cubic volume which the node represents. This includes n1 - n2 pixels
whose colors should be defined by nodes at a lower level in the tree.
Assignment generates the output image from the pruned tree. The output
image consists of two parts: (1) A color map, which is an array of
color descriptions (RGB triples) for each color present in the output
image; (2) A pixel array, which represents each pixel as an index into
the color map array.
First, the assignment phase makes one pass over the pruned color
description tree to establish the image's color map. For each node with
n2 > 0, it divides Sr, Sg, and Sb by n2. This produces the mean color of
all pixels that classify no lower than this node. Each of these colors
becomes an entry in the color map.
Finally, the assignment phase reclassifies each pixel in the pruned tree
to identify the deepest node containing the pixel's color. The pixel's
value in the pixel array becomes the index of this node's mean color in
the color map.
MEASURING COLOR REDUCTION ERROR
Depending on the image, the color reduction error may be obvious or
invisible. Images with high spatial frequencies (such as hair or grass)
will show error much less than pictures with large smoothly shaded areas
(such as faces). This is because the high-frequency contour edges
introduced by the color reduction process are masked by the high
frequencies in the image.
To measure the difference between the original and color reduced images
(the total color reduction error), Display sums over all pixels in an
image the distance squared in RGB space between each original pixel value
and its color reduced value. Display prints several error measurements
including the mean error per pixel, the normalized mean error, and the
normalized maximum error.
The normalized error measurement can be used to compare images. In
general, the closer the mean error is to zero the more the quantized
image resembles the source image. Ideally, the error should be
perceptually-based, since the human eye is the final judge of
quantization quality.
These errors are measured and printed when -verbose and -colors are
specified on the command line:
mean error per pixel:
is the mean error for any single pixel in the image.
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normalized mean square error:
is the normalized mean square quantization error for any single
pixel in the image.
This distance measure is normalized to a range between 0 and 1. It
is independent of the range of red, green, and blue values in the
image.
normalized maximum square error:
is the largest normalized square quantization error for any single
pixel in the image.
This distance measure is normalized to a range between 0 and 1. It
is independent of the range of red, green, and blue values in the
image.
MIFF FILE FORMAT
The Machine Independent File Format is described in this section.
A MIFF image file consist of two sections. The first section is composed
of keywords describing the image in text form. The next section is the
binary image data. The two sections are separated by a : character
immediately followed by a newline. Generally, the first section has a
form-feed and newline proceeding the : character. You can then list the
image keywords with more, without printing the binary image that follows
the : separator.
Each keyword must be separated by at least one space but can be separated
with control characters such a form-feed or newline.
A list of valid keywords follows:
class=DirectClass | PseudoClass
identifies the type of binary image stored within the file.
This keyword is optional. If it is not specified, a DirectClass
image format is assumed. An explanation of DirectClass and
PseudoClass image data follows this list.
colors=value
specifies the number of colors in the image, and for pseudo-color
images the size of the colormap.
This keyword is optional. However, if a colormap size is not
specified, a linear colormap is assumed for pseudo-color images.
columns=value
is a required keyword and specifies the number of columns, or width
in pixels, of the image.
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compression=QEncoded | RunlengthEncoded
identifies how the image stored within the file is compressed.
This keyword is optional. If it is not specified, the image is
assumed to be uncompressed. A detailed explanation of runlength-
encoded and predictive arithmetic image compression follows this
list.
id=ImageMagick
is a required keyword and identifies this file as a MIFF image.
packets=value
specifies the number of compressed color packets in the image data
section.
This keyword is optional, but recommended, for runlength-encoded
image compression. It is required for arithimetic encoded image
compression. A detailed explanation of image compression follows
this list.
rows=value
is a required keyword and specifies the number of rows, or height in
pixels, of the image.
scene=value
is an optional keyword and is a reference number for sequencing of
images.
This keyword is typically useful for animating a sequence of images.
Comments can be included in the keyword section. Comments must begin
with a { character and end with a } character.
An example keyword section follows:
{
Rendered via Dore by Sandy Hause.
}
id=ImageMagick
class=PseudoClass colors=256
compression=RunlengthEncoded packets=27601
columns=1280 rows=1024
scene=1
^L
:
The binary image data that follows the keyword text is stored in one of
two binary classes as specified by the class keyword: DirectClass or
PseudoClass.
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Use the DirectClass class to store continuous-tone images. DirectClass
requires that the image pixels immediately follow the keyword text and be
stored as binary red, green, and blue intensity values. The total number
of pixels expected is equal to the number of pixel columns times the
number of pixel rows as specified by the columns and rows keywords.
If the compression keyword is not specified, a red, green, and blue byte
in that order is expected for each pixel of the image.
If compression is QEncoded, each red, green, and blue byte intensity
value is encoded using the predictive arithmetic compression algorithm.
Use the packets keyword to specify the total number of arithimetic
encoded packets that comprise the image. Refer to "JPEG-9-R6 Working
Draft for Development of JPEG CD", January 1991, for implementation
specific details.
If compression is RunlengthEncoded, each red, green, and blue byte
intensity value is followed by a count byte. This value specifies the
number of horizonally contiguous pixels in the image of that color. The
count (0-255) is one less than the actual number of contiguous pixels;
thus a single packet can represent from 1 up to 256 identical pixels.
The total number of pixels specified by the individual count bytes must
add up to the number of pixel columns times the number of pixel rows as
specified by the columns and rows keywords. Use packets to specify the
total number of runlength-encoded packets that comprise the image.
Use the PseudoClass class to store pseudo-color images. PseudoClass
requires that the image colormap and pseudo-color pixels immediately
follow the keyword text. The colormap is stored as contiguous red,
green, and blue intensity values. The number of intensity values
expected is determined by the colors keyword. Note, an image colormap is
restricted to at most 65535 entries. The binary pseudo-color image is
stored as indexes into the colormap. If the colormap size exceeds 256
entries, then each colormap index is two bytes each with the most-
significant-byte first. The total number of pixels expected is equal to
the number of pixel columns times the number of pixel rows as specified
by the columns and rows keywords.
If the compression keyword is not specified, a colormap index is expected
for each pixel of the image.
If compression is QEncoded, each colormap index is encoded using the
predictive arithmetic compression algorithm. Use the packets keyword to
specify the total number of arithimetic encoded packets comprise the
image. Refer to "JPEG-9-R6 Working Draft for Development of JPEG CD",
January 1991, for implementation specific details.
If compression is RunlengthEncoded, each colormap index is followed by a
count byte. This value specifies the number of horizonally contiguous
pixels in the image of that color. The count (0-255) is one less than
the actual number of contiguous pixels; thus a single packet can
represent from 1 up to 256 identical pixels. The total number of pixels
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DISPLAY(1) X Version 11(1 July 1991) DISPLAY(1)
specified by the individual count bytes must add up to the number of
pixels expected in the image as specified by the columns and rows
keywords. Use packets to specify the total number of runlength-encoded
packets that comprise the image.
FEATURES
Although Display will display an image on a server with an immutable
colormap, the image quality may suffer as compared to a server with a
read/write colormap.
Display memory requirements is proportionate to the area of the image.
Display does not complain when it encounters a keyword in an image file
it does not understand.
ENVIRONMENT
DISPLAY
To get the default host, display number, and screen.
SEE ALSO
X(1), xcmap(1), import(1), XtoPS(1), more(1), compress(1)
COPYRIGHT
Copyright 1991 E. I. du Pont de Nemours & Company
Permission to use, copy, modify, distribute, and sell this software and
its documentation for any purpose is hereby granted without fee, provided
that the above copyright notice appear in all copies and that both that
copyright notice and this permission notice appear in supporting
documentation, and that the name of E. I. du Pont de Nemours & Company
not be used in advertising or publicity pertaining to distribution of the
software without specific, written prior permission. E. I. du Pont de
Nemours & Company makes no representations about the suitability of this
software for any purpose. It is provided "as is" without express or
implied warranty.
E. I. du Pont de Nemours & Company disclaims all warranties with regard
to this software, including all implied warranties of merchantability and
fitness, in no event shall E. I. du Pont de Nemours & Company be liable
for any special, indirect or consequential damages or any damages
whatsoever resulting from loss of use, data or profits, whether in an
action of contract, negligence or other tortious action, arising out of
or in connection with the use or performance of this software.
ACKNOWLEDGEMENTS
The MIT X Consortium for making network transparent graphics a reality.
Michael Halle, Spatial Imaging Group at MIT, for the initial
implementation of Alan Paeth's image rotation algorithm.
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DISPLAY(1) X Version 11(1 July 1991) DISPLAY(1)
David Pensak, E. I. du Pont de Nemours & Company, for providing a
computing environment that made this program possible.
Paul Raveling, USC Information Sciences Institute, for the original idea
of using space subdivision for the color reduction algorithm. With
Paul's permission, the COLOR REDUCTION ALGORITHM section is a adaptation
from a document he wrote.
AUTHORS
John Cristy, E.I. du Pont de Nemours & Company Incorporated
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