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3 Viewing and Comparing multiple Images and Cubes


The <kvis> programme allows you to view multiple datasets.

This tool allows you to compare different datasets in a very easy fashion. You can display any dataset as an image, overlay contours of datasets, show profiles along any axis, and much more. The programme uses the ImageDisplay widget (section 2.15) to provide the usual interface.

3.1 Overview

The tool is centred around the concept of a blink-state, which defines how you want to display datasets (i.e. which dataset is shown as the image, which datasets are shown as contours, how to control movies and profiles and so on). A blink-state can control the display settings of all datasets that have been loaded into the application.

Multiple blink-states may be created, each with a different configuration of what datasets are to be shown. By pressing a key, the display is switched from one blink-state to another.

Blink-states are created and managed using the DataBrowser widget.

3.2 View Control

Pressing the View button will pop up the ViewDatasets widget.

   This widget provides controls for a display window to manage the display of multiple datasets. Most of the controls for data display management are in the DataBrowser widget.

The controls provided are:

  In addition, if you click the left mouse button in the display window without moving it in between the press and release, the image will pan across. If you click the middle mouse button, the image will zoom in 2x (the new centre of the image will be the place where you clicked). Click the right mouse button to zoom out 2x. If the profile mode is ``box'' then you can't use the middle mouse button to zoom.

     Pressing the c key in the display window will compute and display a scatter plot of intensity values in the image dataset versus intensity values in the ``alternate'' dataset. This is useful for seeing if there is a correlation between the values in two images. You can use the left mouse button to define a sub-image (similarly to zooming in) from which the scatter plot is computed.

A screen snapshot is available here.

3.3 Data Browser

     This widget provides controls for managing the display of multiple datasets.

A screen snapshot is available here.

The controls provided are:

Browser Controls

Data List

Beneath these general controls, the list of loaded data appears. Each line shows the name and a summary of the configuration settings for that dataset. The list section is different for each data type. There are common operations that may be performed irrespective of data type, which are described here.

There is always a highlighted line, which shows which entry you can make changes to (using either the mouse buttons or the keyboard). The highlighted line is shown by a slightly different background colour. You can change the highlighted line by using the mouse or up/down arrow keys.

There is also a selected line, which shows which entry has more detail shown in the section(s) below. The list section only shows a summary of the current configuration for each dataset. The selected line is shown by using reverse video.

If the browser is in active mode (the default), then the selected line is locked to the highlighted line. If in passive mode, the selected line does not move until you explicitly select an entry.

If you select an entry while in active mode, the browser switches to passive mode. If in passive mode and you select the already selected entry, the browser switches to active mode.

As the mouse is moved over the data names, one of the names will be highlighted. The mouse and keyboard may be pressed to control the settings of the highlighted data. The following bindings are available:

There are other key bindings which are independent of which dataset the mouse is highlighting:

The list section will show single character codes in a number of columns to the left of the data entry names. Different data types will show a different number of columns, and the character codes have different meanings as well. However following convention is followed:

Below the list of data, more detailed information and configuration settings are shown. The appearance depends on the kind of data being shown.

The configuration controls for the different data types are described below.

Data Replacement


As discussed above, a dataset may be selected for replacement. When a new dataset is loaded, the list of already loaded datasets is scanned for a dataset which has been selected for replacement, and was loaded from the same data source. A typical data source is a file browser, but may also include network connections. When a dataset is replaced with a new one, either all the old settings (such as intensity range, contour levels, etc.) are retained or none of the settings are retained, depending on which replacement mode was selected.

If more than one dataset is selected for replacement, and these datasets were loaded from the same data source, the selected dataset closest to the top of the list is replaced.

Note that if a data source is removed (e.g. a file browser is destroyed), then datasets loaded via that data source can no longer be replaced. These datasets can still be explicitly unloaded, however.

Array List

There are several columns used to display a summary of the configuration, using a simple legend. These are described below:

The following keyboard and mouse bindings are available to quickly control the configuration:

Detailed Array Information

This shows information about the array, such as the directory from where the array was loaded, the format of the data (i.e. FITS, AIPS, Miriad, Gipsy and many more), the size and dimensionality and the range of data values. The following control buttons are available:

Note that these operations affect all browsers/blink-states and all display windows.

Array Configuration

How to display an array is controlled via this section. Some controls are per blink-state, while others are global and apply to all blink-states and all display windows. The following controls are per blink-state:

The following controls are global to the application, and affect all blink-states and display windows:

Advanced Control Panel


This control panel allows you to control some extra aspects of the behaviour of all data browsers. The following controls are available:

Make Data Control Panel


This control panel allows you to create new array data from existing array data. This is useful if you want to combine data together. The following controls are available:

Annotation List

There is just one column used to display a summary of the configuration. The a character is used to indicate whether a annotation file is active (visible) or not. The a key may be used to switch between the two states. The middle mouse button has the same effect of switching between the two states.

Detailed Annotation Information

This shows where directory from which the annotation file was loaded. the Unload button may be used to unload the annotation file. This affects all blink-states and display windows.

Annotation Configuration

The Active toggle may be used to switch between active (visible) and inactive settings for this annotation file.

Command-line Options


You may pass the names of files to be loaded via the command-line. You may specify as many files as you desire, up to the limit imposed by the operating system.

Intensity-Intensity Scatter Plots


Earlier in this chapter (3.2) is a brief description of how you can use the c key to compute and display an intensity-intensity scatter plot of two images. You may also use this facility to display a scatter plot of two channels from the same cube. Simply clone the cube (i.e. using the Clone data browser button), and select the two channels, one from each cube. You will need to ensure that the original and cloned cube do not have a master/slave movie relationship.

If there is a master/slave movie relationship, then the scatter plot is computed using the two frames which have corresponding co-ordinates for the frame axes. This is usually the desired setting when generating scatter plots from frames of two different cubes.

Note that when computing a scatter plot from two images with a different co-ordinate grid, the pixels from the unseen image correspond to pixels with the same world co-ordinates in the visible image. Thus, there is no need to re-grid either of the images.

3.6 Renzograms, an alternative to velocity fields


A ``renzogram'' is a technique for displaying velocity information in a cube in a different (better) way than velocity fields. The technique was pioneered by Renzo Sancisi at the Kapteyn Institute in Groningen. A ``renzogram'' overlays a single-level contour map for every channel in a cube over an image (such as an optical image or moment map). The contour map for each channel is displayed in a different colour (typically red-blue, although this can be changed interactively). This has an advantage over velocity fields because it shows multiple peaks in the velocity profile, which a velocity field cannot do.

To use this feature, simply load a cube and select it for renzogram display in the data browser. You can control the contour level used for the renzogram, and the range of channels displayed.

You may wish to load a separate image (perhaps an optical image) and display that as the image. This can be useful for comparing optical and radio data.

You can also view a profile (spectrum) of your cube. Just select select line profile display and a profile window will appear. You will note that the profile is drawn in the same colours as the contours.

A screen snapshot of the older <krenzo> programme is available here

next up previous contents index Karma Home Page
Next: 4 Viewing Images and Up: Karma User Manual Previous: 2 Common Features

Richard Gooch
Mon Aug 14 22:25:04 PDT 2006