3 Viewing Images and Cubes

      

The <kview> and <MultibeamView> programmes allow you to view two datasets. This allows you to compare different datasets in a very easy fashion. Both these programmes use the ImageDisplay widget (section 2.15) to provide the usual interface. Pressing the View button will pop up the View2Datasets widget.      This widget provides an advanced control for two datasets (either two-dimensional or three-dimensional). It allows the user to display one dataset or the other, overlay contours of one over the other, show profiles along any axis, and much more. The controls provided are:

• Close this will close the window
• Movie this will pop up the AnimateControl widget (section 2.3)

   

• Blink if enabled, dataset 2 is displayed (if the display mode is set to blink), if disabled, dataset 1 is displayed. By repeatedly clicking this, the user can blink between the two datasets. You can also press the ``b'' key in the image window and get the same effect. Note that when blinking between two images with non-linear co-ordinate systems, the linear (data pixel) co-ordinates of the canvas boundary are preserved, not the non-linear world co-ordinates. This is especially noticable when blinking between two images with a different pixel scale
• Profile Mode Menu this allows you to pop up the TracePopup widget (section 2.11) and choose the profile mode. The following modes are available:
  • None will pop down the TracePopup widget

     

  • Line will show a single profile in the selected direction

     

  • Box Sum lets you draw a box over the image window (using the middle mouse button, in a similar way as using the left mouse button to zoom) and then the sum of all the profiles in that region is displayed. Box mode only works for 3-dimensional datasets

     

  • Box Average is like the box sum mode except that the average of all profiles is displayed rather than the sum

         

  • Radial will azimuthally average the image plane data and produce a plot of average value versus radius. A gaussian is then fitted to the radial profile and overplotted in red and the FWHM (full width half max) of the gaussian is displayed over the profile. You must click the middle mouse button to define the centre of the object of interest, then, keeping the mouse button down, drag out to define the maximum radius of the profile and release the button to display. The algorithm automatically adjusts the centre position using a centroiding operation, so you don't have to be too careful about picking the centre of your object.

    The programme should also work with a photographic negative. The centroiding algorithm is automatically modified to look for a trough rather than a peak

     

  • Boxed Horiz will produce a horizontal profile which is averaged vertically. The box is drawn the same way as for the box sum mode. The horizontal centroid of the profile is computed and a gaussian is fitted and displayed
  • Boxed Vert will produce a vertical profile which is averaged horizontally. The box is drawn the same way as for the box sum mode. The vertical centroid of the profile is computed and a gaussian is fitted and displayed
• Slice Direction Menu this allows you to choose how you want to slice your cube. You can view XY, XZ or ZY planes
• Profile Axis Menu this allows you to choose along which axis you want the profile to be displayed (valid only for line profile mode)
• Display Mode Menu this allows you to choose how you want to view your two datasets. The following choices are available:

    

  • Set 1->image view dataset 1 as an image
  • Set 2->image view dataset 2 as an image
  • Set 1->image, Set 2->contour view dataset 1 as an image and overlay dataset 2 as contours
  • Set 1->contour, Set 2->image view dataset 2 as an image and overlay dataset 1 as contours
  • Blink between Set 1 and Set 2 enable blinking between the two datasets
• Contour Levels this controls the contour levels. Be careful not to hit return after filling in the levels!!! The syntax for the contour levels is as follows:

   

  • just type the levels you want eg. 0.001 0.002 0.003 0.004
  • levels with a constant increment: 0.001:0.004+0.001 means that the first level is 0.001, that this level is incremented with 0.001 until 0.004 is reached. So this example gives the same levels as in the first case
  • levels incremented by a factor: 0.001:0.016*2. This gives levels 0.001 0.002 0.004 0.008 0.016
  • levels as percentage of the peak: first character should be %, numbers are taken as percentage, the rest of the syntax is as above, e.g. %10:40+10 gives 10, 20, 30 and 40 % of the maximum of the data

  These options can be mixed, i.e. -0.03:-0.01+0.01 0.003:0.1+0.02 0.2 0.3 is interpreted correctly.

• Contour Colour specifies the colour the contours should be drawn in
• Apply Levels this will apply the contour levels and colour
• Reset Levels will reset the contour levels to the default
• Auto Apply if this is on, then if you load a new dataset over one that is currently being displayed as contours, the old contour levels are automatically applied. The reason this is off by default is because the contour levels for one dataset may be incorrect for another. An inappropriate set of contours can take a long time to display, so mistakes are costly
• Axis Labelling Title this allows you to change the title placed above the image when axis labelling is enabled. Normally, the title is automatically generated
• -ve Contour Width this controls the width of negative contours
• +ve Contour Width this controls the width of positive contours
• Link Intensity Scales if this is set then if the intensity scale for either dataset is modified using the Dataclip (section 2.2) widget then the intensity scaling for both datasets is changed. This can be useful when blinking between two images
• Auto Title if enabled, the axis labelling title is automatically generated. Whenever this is disabled, the string specified by Axis Labelling Title is used instead
• Show Beam if enabled, the dataset headers are searched for ``BPA'', ``BMAJ'' and ``BMIN'' FITS-style keywords. If these keywords are present, a representation of the telescope beam is overlaid on the image
• Show Beam Name if enabled, the name of the dataset for each beam is placed near the beam representation
• Set 1 Beam Xpos controls the horizontal position of the the beam for dataset 1
• Set 1 Beam Ypos controls the vertical position of the the beam for dataset 1
• Set 2 Beam Xpos controls the horizontal position of the the beam for dataset 2
• Set 2 Beam Ypos controls the vertical position of the the beam for dataset 2

  In addition, if you click the left mouse button 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.

A screen snapshot is available here.

Command-line Options

 

The following command-line options are supported by <kview> and <MultibeamView>:

• -set1 <filename> this will load the dataset filename as set 1
• -set2 this will load the dataset filename as set 2

3.2 Special Movies

  

If you want to play a movie that was made using the Hot Gas Substances or the Hot Gas Continuous shaders of the xray volume rendering tool, you should compress this movie from 24-bit to 8-bit. Movies made with the other algorithms do not require compression and can be played directly. The compression of 24-bit movies is done with the command:

conv_24to8 -com w -max <max num of colours> - <inmovie>

The switch -com w tells the program that it should compress such that it has the same colourmap for all the images. In principle you could leave out this switch, but that is not recommended. Your movie will look awful.

The switch -max <max num of colours> gives the maximum number of colours the final movie can have. The recommended value to use is -max 200. Do not give a higher number than 220.

Please note the space between the name of the movie and the minus-sign.

You do not have control over the name of the output file. The string conv_24to8_ is prepended to the name of the input file:

conv_24to8 -c w -m 200 - ugc12441_movie

produces a file conv_24to8_ugc12441_movie.kf (!) with the compressed movie.

3.3 Multiple Contour Images

 

The <kview> and <MultibeamView> programmes only support displaying one dataset as contours. If you wish to display multiple datasets as contours, you will also need to use the <send-contours> programme to display the second, third and further contoured datasets.

A future version of <kview> will support loading of multiple datasets and drawing multiple images as contours. However, this is a major project, so in the meantime the <send-contours> programme will need to be used.