.\

activecontour.pro

top ActiveContour

Graphics, Analysis

ActiveContour [, image] [, x] [, y] [, ALPHA=float] [, BETA=float] [, /BLUR] [, COLOR=string] [, DELTA_MAX=float] [, DELTA_MIN=float] [, DRAWID=long], NOTIFY_EVENT=NOTIFY_EVENT [, GAMMA=float] [, KAPPA=float] [, GRADIENTSCALE=float] [, GVF_ITERATIONS=integer] [, MAX_VALUE=varies] [, MIN_VALUE=varies] [, MU=float] [, PALETTE=byte] [, SIGMA=float] [, SPATIAL_SCALE=double] [, ITERATIONS=integer]

This program allows the user to experiment with a Gradient Vector Flow active contour algorithm, as described by Chenyang Xu and Jerry L. Prince in "Snakes, Shapes, and Gradient Vector Flow" in the March 1998 IEEE Transactions on Image Processing, Vol. 7, No.3. Additional information, including references to research papers, is available via Cheyang Xu's web page.

Active contours are also described as "snakes", because they writhe and move under the influence of external and internal forces, toward a feature of interest in an image, usually an edge. This program gives the user the opportunity to control both external and internal forces to find an optimal set of active contour parameters. Active contours are most often used with images to find and describe regions of interest.

The Coyote Library is required to run this program.

This program set can be purchased from the Coyote Store.

Parameters

image in optional

The image for which the active contour (snake) will be applied. This argument must be 2D. The user will be asked to select an image file if this argument is not provided.

x in optional type=float

The initial X points of the active contour or snake. Optional. Must be used with Y.

y in optional type=float

The initial Y points of the active contour or snake. Optional. Must be used with X.

Keywords

ALPHA in optional type=float default=0.10

The elasticity parameter of the active contour. It reflects the contour's ability to stretch along its length.

BETA in optional type=float default=0.25

The rigidity parameter of the active contour. It reflects the contour's ability to bend, as, for example, around corners.

BLUR in optional type=boolean default=1

Set this keyword to 1 if you want a Gaussian Blur applied to image before processing. Set it to 0 otherwise.

COLOR in optional type=string default=red

The name of a color for the snake. See the documentation for cgColor for a list of possible color names.

DELTA_MAX in optional type=float default=5.50

The maximum pixel distance for adaptive interpolation.

DELTA_MIN in optional type=float default=0.25

The minimum pixel distance for adaptive interpolation.

DRAWID in optional type=long

The draw widget identifier where the image is displayed. The image CANNOT be displayed in a normal IDL graphics window. The event handler for this draw widget will be changed for snake processing, and then returned to its original state when the Active Contour control panel is destroyed. If this parameter is not supplied or is invalid, the program will create its own display window.

NOTIFY_EVENT

GAMMA in optional type=float default=1.0

The viscosity parameter. Larger values make it harder to deform the active contour in space.

KAPPA in optional type=float default=1.25

The external force weight.

GRADIENTSCALE in optional type=float default=1.75

A multiplication factor for the gradient calculations.

GVF_ITERATIONS in optional type=integer default=30

The number of iterations for calculating the Gradient Vector Flow (GVF).

MAX_VALUE in optional type=varies

The maximum value for scaling the image data for display.

MIN_VALUE in optional type=varies

The minimum value for scaling the image data for display.

MU in optional type=float default=0.10

The regularization parameter. This should be set according to the amount of noise in the image. Use a larger value for noisier images.

PALETTE in optional type=byte

A 256x3 byte array containing the color table vectors for display of the image.

SIGMA in optional type=float default=1.0

The standard deviation or sigma of the Gaussian function used in Gaussian blurring.

SPATIAL_SCALE in optional type=double

Set this keyword to a two-element array that specifies the pixel scale in the X and Y directions ([xscale, yscale]). The scale factors are applied when the perimeter and area calculations for the final contour is made. Default is [1.0D, 1.0D].

ITERATIONS in optional type=integer default=120

The number of iterations to use in calculating the snake positions.

Author information

Author:

FANNING SOFTWARE CONSULTING:

  David W. Fanning
  1645 Sheely Drive
  Fort Collins, CO 80526 USA
  Phone: 970-221-0438
  E-mail: david@idlcoyote.com
  Coyote's Guide to IDL Programming: http://www.idlcoyote.com

Copyright:

History:

Modification History:

  Written by David W. Fanning, 1 December 2003.
  Removed the Coyote Library from the ActiveContour distribution. 15 June 2005.
  Extensive updates for the latest Coyote Library routines and to make the
     program easier to use. 24 Oct 2011. DWF.

File attributes

Modification date:	Fri Oct 25 18:07:48 2013
Lines:	205
Docformat:	rst rst

Coyote Graphics Active Contour Routines