isomap -- Draw image contours with superposed ellipses.
isomap image table floor ceiling
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.
- 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.
Supperposition of contours and ellipses may lack precision when using image sections with stepping, due to numerical truncation effects.
This task was written by I.Busko