NAME
segment - segments an image with thresholding and the fuzzy
c-Means technique.
SYNOPSIS
segment [ options ... ] input_file output_file
DESCRIPTION
segment segments an image by analyzing the histograms of the
color components and identifying units that are homogeneous
with the fuzzy c-means technique. The scale-space filter
analyzes the histograms of the three color components of the
image and identifies a set of classes. The extents of each
class is used to coarsely segment the image with
thresholding. The color associated with each class is
determined by the mean color of all pixels within the
extents of a particular class. Finally, any unclassified
pixels are assigned to the closest class with the fuzzy c-
means technique.
The fuzzy c-Means algorithm can be summarized as follows:
o Build a histogram, one for each color component of
the image.
o For each histogram, successively apply the scale-
space filter and build an interval tree of zero
crossings in the second derivative at each scale.
Analyze this scale-space ``fingerprint'' to determine
which peaks or valleys in the histogram are most
predominant.
o The fingerprint defines intervals on the axis of the
histogram. Each interval contains either a minima or a
maxima in the original signal. If each color component
lies within the maxima interval, that pixel is
considered ``classified'' and is assigned an unique
class number.
o Any pixel that fails to be classified in the above
thresholding pass is classified using the fuzzy c-Means
technique. It is assigned to one of the classes
discovered in the histogram analysis phase.
The fuzzy c-Means technique attempts to cluster a pixel by
finding the local minima of the generalized within group sum
of squared error objective function. A pixel is assigned to
the closest class of which the fuzzy membership has a
maximum value.
For additional information see
Young Won Lim, Sang Uk Lee, "On The Color Image
Segmentation Algorithm Based on the Thresholding and
the Fuzzy c-Means Techniques", Pattern Recognition,
Volume 23, Number 9, pages 935-952, 1990.
EXAMPLES
To segment an image of a cockatoo, use:
segment cockatoo.miff cockatoo.segmented
To segment a raw grayscale image, use:
segment -size 768x512 gray:raw image.miff
OPTIONS
-cluster_threshold value
eliminate clusters that are insignificant.
The number of pixels in each cluster must exceed the
the cluster threshold to be considered valid. The
default is 1%.
-colorspace value
the type of colorspace: GRAY, OHTA, RGB, XYZ, YCbCr,
YIQ, YPbPr, or YUV.
Color reduction, by default, takes place in the RGB
color space. Empirical evidence suggests that
distances in color spaces such as YUV or YIQ correspond
to perceptual color differences more closely than do
distances in RGB space. These color spaces may give
better results when color reducing an image. Refer to
quantize(9) for more details.
-comment string
annotate an image with a comment.
By default, each image is commented with its file name.
Use this option to assign a specific comment to the
image. Optionally you can include the image filename,
type, width, height, or scene number by embedding
special format characters. Embed %f for filename, %m
for magick, %w for width, %h for height, %s for scene
number, or \n for newline. For example,
-comment "%m:%f %wx%h"
produces an image comment of MIFF:bird.miff 512x480 for
an image titled bird.miff and whose width is 512 and
height is 480.
If the first character of string is @, the image
comment is read from a file titled by the remaining
characters in the string.
-compress type
the type of image compression: QEncoded or
RunlengthEncoded.
Specify +compress to store the binary image in an
uncompressed format. The default is the compression
type of the specified image file.
-density <width>x<height>
vertical and horizontal resolution in pixels of the
image.
This option specifies an image density for a Postscript
page. The default is 72 pixels per inch in the
horizontal and vertical direction. The density is
given to Ghostscript as the -r option when decoding a
Postscript image. See gs(1) for details.
-display host:display[.screen]
specifies the X server to contact; see X(1).
-font name
This option specifies the font to be used for
displaying normal text. The default is fixed.
-interlace type
the type of interlacing scheme: NONE, LINE, or PLANE.
This option is used to specify the type of interlacing
scheme for raw image formats such as RGB or YUV. NONE
means do not interlace (RGBRGBRGBRGBRGBRGB...), LINE
uses scanline interlacing
(RRR...GGG...BBB...RRR...GGG...BBB...), and PLANE uses
plane interlacing (RRRRRR...GGGGGG...BBBBBB...).
Use LINE, or PLANE to create an interlaced GIF image.
-label name
assign a label to an image.
Use this option to assign a specific label to the
image. Optionally you can include the image filename,
type, width, height, or scene number in the label by
embedding special format characters. Embed %f for
filename, %m for magick, %w for width, %h for height,
or %s for scene number. For example,
-label "%m:%f %wx%h"
produces an image label of MIFF:bird.miff 512x480 for
an image titled bird.miff and whose width is 512 and
height is 480.
If the first character of string is @, the image label
is read from a file titled by the remaining characters
in the string.
When converting to Postscript, use this option to
specify a header string to print above the image.
-matte
store matte channel if the image has one.
-page <width>x<height>{+-}<x offset>{+-}<y offset>
preferred size and location of the Postscript page.
Use this option to specify the dimensions of the
Postscript page in pixels per inch or a TEXT page in
pixels. The default for a Postscript page is to center
the image on a letter page 612 by 792 pixels. The
margins are 1/2" (i.e. 612x792+36+36). Other common
sizes are:
Letter 612x 792
Tabloid 792x1224
Ledger 1224x 792
Legal 612x1008
Statement 396x 612
Executive 540x 720
A3 842x1190
A4 595x 842
A5 420x 595
B4 729x1032
B5 516x 729
Folio 612x 936
Quarto 610x 780
10x14 720x1008
For convenience you can specify the page size by media
(e.g. A4, Ledger, etc.).
The page geometry is relative to the vertical and
horizontal density of the Postscript page. See
-density for details.
The default page dimensions for a TEXT image is
612x792.
-quality value
JPEG quality setting.
Quality is 0 (worst) to 100 (best). The default is 85.
-scene value
image scene number.
-size <width>{%}x<height>{%}{+colors}{!}
width and height of the image.
Use this option to specify the width and height of raw
images whose dimensions are unknown such as GRAY, RGB,
or CMYK. In addition to width and height, use -size to
tell the number of colors in a MAP image file, (e.g.
-size 640x512+256).
-smoothing_threshold value
eliminate noise in the second derivative of the
histogram.
As the value is increased, you can expect a smoother
second derivative. The default is 1.5.
-verbose
print detailed information about the image.
This information is printed: image scene number; image
name; converted image name; image size; the image
class (DirectClass or PseudoClass); the total number
of unique colors; and the number of seconds to read
and convert the image.
Options are processed in command line order. 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.
Change '-' to '+' in any option above to reverse its effect.
For example, specify +matte to store the image without its
matte channel.
By default, the image format is determined by its magic
number. To specify a particular image format, precede the
filename with an image format name and a colon (i.e.
ps:image) or specify the image type as the filename suffix
(i.e. image.ps). See convert(1) for a list of valid image
formats.
When you specify X as your image type, the filename has
special meaning. It specifies an X window by id, name, or
root. If no filename is specified, the window is selected
by clicking the mouse in the desired window.
Specify input_file as - for standard input, output_file as -
for standard output. If input_file has the extension .Z or
.gz, the file is uncompressed with uncompress or gunzip
respectively. If output_file has the extension .Z or .gz,
the file size is compressed using with compress or gzip
respectively. Finally, precede the image file name with |
to pipe to or from a system command.
Use an optional index enclosed in brackets after a file name
to specify a desired subimage of a multi-resolution image
format like Photo CD (e.g. img0001.pcd[4]).
If output_file already exists, you will be prompted as to
whether it should be overwritten.
ENVIRONMENT
display
To get the default host, display number, and screen.
SEE ALSO
display(1), animate(1), import(1), montage(1), mogrify(1),
convert(1), combine(1), xtp(1)
COPYRIGHT
Copyright 1995 E. I. du Pont de Nemours and 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
and 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 and
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 and 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 and 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 tortuous action, arising out of or in connection with
the use or performance of this software.
ACKNOWLEDGEMENTS
Andy Gallo, University of Delaware. This software is
strongly based on software Andy wrote.
AUTHORS
John Cristy, E.I. du Pont De Nemours and Company
Incorporated