thresMlWaHa
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thresMlWaHa - Finds multiple thresholds by Wang & Haralick method
thresMlWaHa [-n <n>] [-nt <nt>] [-p <p>] [-et <et>] \\
[-verbose] [-tri <trilevel-image>] \\
[-edge <edge-image>] <inimage> <outimage>
The pixels in inimage are first classified as either edge
pixels or nonedge pixels. Edge pixels are then classified, on
the basis of their neighborhoods, as being relatively dark,
relatively bright or gray. A histogram of the graytone
intensities is obtained for those pixels which are edge
pixels and relatively dark, and another histogram is obtained
for those which are edge pixels and relatively bright. Two
candidate thresholds are found at the intensity values
corresponding to peaks in the two histograms. The threshold
giving the highest probability of getting pure dark or bright
regions is selected. If the selected threshold corresponds to
the peak in the dark edge histogram, the process is repeated
for the graytone range above the threshold, if the threshold
corresponds to the peak in the bright edge histogram, the
process is repeated for the graytone range below the
threshold.
You can specify the number of thresholds to be found, or a
minimum population of the two histograms at which to stop.
The population of the two histograms decreases rapidly, and
might reach zero before the specified number of thresholds is
found. There is no peak in a histogram with only zero entries
and the process stops.
-
-n n
- An integer n used to adjust the number of edge pixels
classified as either dark or bright. The number of pixels
classified as either dark or bright increases with
increasing n. Default n = 3.
-
-et et
- Edge threshold et. The sobel magnitude operator is used to find
the edge strenght in every pixel. The edge threshold value
et is then used to classify pixels as edge pixels or
nonedge pixels. Default et = 100.
-
-nt nt
- Number nt of thresholds wanted.
-
-p p
- The minimum population p in dark or bright edge histograms
allowed before stopping. Only one of nt and p may be
specified. If none of them are specified, the default value
p = 100 is used as stop criteria.
-
-verbose
- Verbose. Will cause certain messages to be written to
"stdout". ie. the thresholds found, the poulation of the
dark and bright histograms and the graytone range, and the
total number of thresholds found.
-
-edge edge-image
- Specifies that the thresholded sobel magnitude image
should be written to edge-image.
-
-tri trilevel-image
- Specifies that the classified edge image should be
written to trilevel-image. Edge pixels classified as dark
will be dark, edgepixels classified as bright will be bright,
and other pixels will be gray.
The result written to outimage will be a multithresholded
version of inimage with either nt thresholds (if
possible), or as many thresholds found with significant
populations in both dark and bright histograms.
-
S. Wang and R. M. Haralick
- "Automatic Multithreshold Selection".
Computer Vision, Graphics, and Image Processing,
25, 46-67 (1984).
thresMl(1), thresMlAppScale(3), thresMlAppMean(3),
thresMlAppMedian(3), thresMlApply(3), histoCentroid(3),
thresMlCentroid(3), thresMlCentroid(3), mkComCur(3),
thresMlComCur(3), thresMlComCur(1), thresMlReddi(3),
thresMlReddi(3), thresMlWaHa(3), sobel(1)
inimage must have bands with pixel type unsigned byte.
0 => OK.
1 => Bad number of arguments.
2 => Cant open inimage.
3 => Malloc error.
4 => Error in thresMlWaHa function.
Jørn Tilley Jacobsen, BLAB, Ifi, UiO
thresMlWaHa solflekk.img solSeg.img
thresMlWaHa -nt 5 -n 2 -et 50 -verbose -edge solE.img \\
-tri solT.img solflekk.img solSeg.img
$Id: thresMlWaHa.c,v 1.22 1997/01/14 13:09:28 svein Exp $