isomap: Plot ellipses superposed over image contours.

Package: isophote

Usage

isomap image table floor ceiling

Description

The 'isomap' task draws a contour map from a 2-dimensional image and superposes ellipses on it corresponding to intensity levels. Ellipse data is taken from a table created by the 'ellipse' task.

This task is a script which calls the tasks 'tsort' and 'trebin' in the 'ttools' package. These tasks create a temporary table with an interpolated version of the original input table. This temporary table is then fed to the hidden task 'map', which creates a set of temporary files containing coordinates of ellipse points. The 'plot.contour' task is then invoked to draw contours, and finally, the 'stplot.sgraph' task uses the temporary ellipse point files to draw the ellipses.

The intensity interval to be contoured is specified by the parameters 'floor' and 'ceiling'. Care must be taken with these parameters, because the 'trebin' task can also extrapolate from the original data, and meaningless results could be generated in some cases. Linear interpolation is used. The 'nlevels' parameter specifies the number of levels to be contoured, up to 10.

The packages 'ttools', 'stplot', and 'plot' must be loaded before using this task.

Parameters

image [file name]: Input image to be contoured.

table [file name]: Table containing the results of isophotometry analysis (i.e., the table produced by 'ellipse').

floor [real]: Minimum level to be contoured.

ceiling [real]: Maximum level to be contoured.

(nlevels = 3) [integer, min=2, max=10]: Number of contours.

(device = "stdgraph") [string]: Graphics output device.

Examples

Bugs

Supperposition of contours and ellipses may lack precision when using image sections with stepping, due to numerical truncation effects.

References

This task was written by I.Busko