.ds Vi Vista
.ds Vn 2.1
.TH vdist3d 1Vi "17 August 1994" "\*(Vi Version \*(Vn"
.SH NAME
vdist3d \- perform a 3D distance transform
.SH SYNOPSIS
\fBvdist3d \fB [-\fIoption\fP ...] [\fIinfile\fP] [\fIoutfile\fP]

.SH DESCRIPTION
\fBvdist3d\fP performs a 3D
distance transform on the \fIsource\fP image
to produce a file of a distance transformed \fIdestination\fP image.  
Each pixel in the output image contains the distance to the nearest
feature element measured in a Euclidean or Chamfer metric.
If needed, three images containing the addresses of the nearest
foreground pixels will also be produced.

.LP
The input image must be of type VBit. The output image
will be of type VFloat. If present, 
the vector images will be of type VShort.

.LP
Input and output files can be specified on the command line or
allowed to default to stdin and stdout.

.LP
If the metric is \fIeuclidean\fP, and no vectors are needed,
the algorithm used is Saito/Toriwaki's algorithm.
If the metric is \fIeuclidean\fP, but vectors are needed,
then Daniellson's algorithm is used.
For the chamfer metric the algorithm by Borgefors
is used.
Note that Daniellson's algorithm is the most expensive
(both w.r.t computing time as well as w.r.t space).
The second most expensive algorithm is Saito/Toriwaki's.
However, it is not possible to obtain the distance vectors from
this algorithm.
The cheapest is Borgefors's, which also does not yield
the distance vectors.

Note that in some rare cases, Daniellson's algorithm fails.
In that case, use Saito's algorithm (which always works)
and do without the distance vectors.


.SH LITERATURE
Toyofumi Saito, Jun-Ichiro Toriwaki,
New algorithms for euclidean distance transformation of a n-dimensional
picture with applications,
Pattern Recognition, Vol. 27, No. 11, pp 1551-1565, 1994.

Gunilla Borgefors,
"Distance Transformations in Arbitrary Dimensions",
Computer Vision, Graphics and Image Processing,
Vol 27, pp. 321-345, 1984.

P.-E. Daniellson,
"Euclidean Distance Mapping",
Computer Graphics and IMage Processing,
Vol. 14, pp. 227-248, 1980.


.SH "COMMAND LINE OPTIONS"
\fBvdist3d\fP accepts the following options in any order:
.IP \fB-help\fP 1.5i
Causes \fBvdist3d\fP to print out a message describing its options.
.IP "\fB-metric\fP \fIeuclidean/chamfer\fP"
Determines which metric to use.
.IP "\fB-vector\fP \fIyes/no\fP"
Determines whether or not a vector image will be produced.
Default: no.

.SH "SEE ALSO"
.BR Vista (7Vi)
.SH AUTHOR
Gabriele Lohmann <lohmann@cns.mpg.de>