HESSI Image Widget

Click here to see the entire HESSI GUI Guide


Imaging Parameters

     Selecting Input Source

     Selecting Time and Energy Intervals
     Selecting Collimators, Harmonics, Time bins
     Selecting Image Algorithm
Making Images
Viewing Images

Cross Reference Tables for Widget Names and Object Parameters


     CLEAN Algorithm

     MEM Sato, MEM VIS Algorithms

     Pixon Algorithm

     Forward Fit Algorithm

     Snapshot of Image and Movie Widget



The HESSI Image Widget is a graphical interface to the HESSI image object. The object and the interface are connected closely; the interface provides an easy way to set parameters in the object and call the process method of the object to generate an image.

This widget is activated when you click File / 'Retrieve/Process Data' / Image in the Main GUI Window.

Note:  This widget interface changed significantly in March 2005 to work with the new image object that handles image cubes.  The most significant new features are discussed below in the 'Selecting Input Source' and 'Viewing Images' sections.


Imaging Parameters

When you enter the Image Widget, the current values of imaging parameters are reflected in the widget values.

The only parameter that will be set for you, and only if you've selected a new time interval or flare, is the default imaging time interval which will be set to 4 seconds at the peak of the flare.

When you change any of the imaging parameters, they are set in the image object, and are remembered the next time you enter the image widget.  You can reset the parameters to default values by clicking the 'Reset to defaults' button.

This document describes how to use the widgets to set parameters, but will not attempt to explain how the image algorithms work or what the image object parameters mean.  Refer to the Imaging section of the RHESSI Data and Software Center  for a complete description of the image algorithms and the HESSI Data Object Parameter tables for a list of the control and info parameters that apply to imaging.  Below are cross-reference tables showing the object control parameter names corresponding to the names in the widgets.

Changing most of the parameters is straightforward.  The ones that aren't are described below.

Selecting Input Source

There are three input choices:

Selecting Time and Energy Intervals

To select time and/or energy intervals, click the 'Change...' button on the Image Widget.  The 'Select Intervals' widget that appears shows the intervals that are currently defined.  There are several ways to change the intervals:

  1. Below the area  that shows the currently defined intervals, there are buttons that let you edit or delete a single interval (select which one by highlighting it in the droplist), or edit or delete the entire list.  To edit, simply change the text in the XTEXTEDIT window, and click 'Finished editing'.  Be careful not to change the format of the interval entries.
  2. If your current plot is of the right type (time or energy on x axis), you can choose to define intervals graphically.
  3. You can read intervals from a file you created in this widget previously using the 'Save Current Intervals to File' button.
  4. Or you can define an interval manually, and
    • either add it to the current list or replace the current list
    • create n intervals starting from that start time with that delta and either add them to the current list or replace the current list
    • create n intervals by dividing that interval into n evenly spaced intervals and either add them to the current list or replace the current list

Note:  in each case you must click either the 'Add to List' or the 'Replace List' button to move the intervals into the current list.  Click Accept to transfer these intervals to the Image Widget.  Note that in the Image Widget, the pull-down widget showing the current intervals is for display only; you can not select an interval using that pull-down widget.  To change your selection, you must click the 'Change' button again.

Selecting Collimators, Harmonics, Time bins

To change collimator options, click the Change button in the collimator box. 

Note: As of October, 2001, the following options are not available:

If the 'Calculate time bins automatically' box is enabled, then the Time Bin column for each collimator is insensitive.  If it is disabled, then you can set the elements in the Time Bin column.  These elements are the multipliers on Time_Bin_Minimum for each collimator.  The units for the time bins are binary microseconds (bus).  (There are 1024 binary microseconds in a millisecond.)  Notice that the result of the multiplier on the Time Bin Minimum is shown in the column to the left of the editable fields.

Selecting Image Algorithm

Use the droplist to select the image algorithm.  For all algorithms except Back Projection you can set options to control the reconstruction process by clicking the 'Set Parameters' button.

If the Clean algorithm is selected, one of the options available is 'Define/Modify clean boxes after BPROJ'.  If this option is enabled, then after the Clean routine makes the Back Projection map (which is always its first step), it will pause and display the map with an accompanying  widget that allows you to draw one or more regions on the image.   When you have finished defining the 'clean boxes', the Clean routine will resume, but will limit its search for maxima to those regions.  The next time you make an image with Clean, it remembers and uses the boxes that were defined previously.  You have the option to delete them or redefine them.  Another way to set the 'clean boxes' is by clicking the 'Mark Clean Boxes' button in the main Image widget.  This button becomes active only if there is an image (any algorithm) displayed in the Main GUI Window, and the image algorithm selection is set to Clean.  

Making Images

After setting the parameters you want to change, clicking 'Make/Plot  Images', 'Write FITS file', 'Panel Display', or 'Movie' will start generating the images.     There are options  to give you more information while generating the images including a progress bar with a Cancel button, verbose mode to print more text in the IDL output log, and an option to show each image in a little window while they're being generated (these images are not brought into the GUI, but are available just so you can see whether the images look all right).

Note that some of the reconstruction algorithms can take a very long time to make an image.  Back Projection is usually the fastest, but produces the least reliable image.  Clean, MEM Sato, and MEM Vis depend on the number of iterations or Lambda values you ask for.  And Pixon can take hours, but does a very good job.

For all algorithms except Back Projection, a progress/cancel widget (this is in addition to the overall image cube progress bar) appears while the reconstruction is in progress (unless you disabled this option) that gives you an estimate of the percent completed, and has a 'Cancel' button to let you interrupt the reconstruction.  If you click the cancel button, then the image that has been created so far will be displayed.  If  the reconstruction had not gotten far enough to even make the first attempt at an image, then nothing will be returned or displayed.

Viewing Images

Note that all three of these options will cause reprocessing of the images if you have changed any control parameters or haven't generated the images yet.



Table 1.   Image Widget Names Cross-Referenced to Object Parameter Names

Widget Name Object Parameter Name
Image Time Interval im_time_interval, im_time_bin, obs_time_interval, time_range
Energy Band im_energy_binning, energy_band
Collimator det_index_mask
Harmonics det_index_mask
Time bin time_bin_def
Time Bin Minimum time_bin_min
Front/Rear front_segment, rear_segment
Calculate time bins automatically use_auto_time_bin
Force multipliers to powers of two cbe_powers_of_two
Digital quality cbe_digital_quality
Pixel Size pixel_size
Image Dimensions image_dim
Offset of Map Center from Sun Center xyoffset
Image Algorithm image_algorithm
Flatfield flatfield
Modpat_skip modpat_skip
Weighting natural_weighting, uniform_weighting
Tapering Width taper
Simulated Aspect Solution aspect_sim
Variable Flux Correction use_flux_var
Flux Smoothing Time smoothing time


Table 2.  Clean Algorithm Widget Names Cross-Referenced to Object Parameter Names

Widget Name CLEAN Parameter Name
Gain clean_frac
Chi-square goal clean_chi_sq_crit
Max # iterations clean_niter
No chi-square test clean_no_chi2
Stop if negative max clean_negative_max_test
Restart from last clean clean_more_iter
Show progress clean_show_maps
Show Chisquare Test clean_show_chi
Show progress/cancel bar clean_progress_bar
Define/Modify clean boxes after BPROJ clean_mark_box


Table 3.  MEM Sato MEMVIS Algorithm Widget Names Cross-Referenced to Object Parameter Names

Widget Name Sato Parameter Name VIS Parameter Name
Lambda max sato_lambda_max vis_lambda_max
Chi-square goal sato_chi_limit vis_chi_limit
Max # iterations sato_iter_max vis_iter_max
Smoothness Constraint sato_lnorm vis_lnorm
No chi-square test sato_no_chi2 vis_no_chi2
Show progress sato_show_image vis_show_image
Show progress/cancel bar sato_progress_bar vis_progress_bar


Table 4.  Pixon Algorithm Widget Names Cross-Referenced to Object Parameter Names

Widget Name Pixon Parameter Name
Show Progress pixon_noplot
Show progress/cancel bar pixon_progress_bar


Table 5.  Forward Fit Algorithm Widget Names Cross-Referenced to Object Parameter Names

Widget Name Forward Fit Parameter Name
# Sources ff_n_gaussians
# Parameters per Source ff_n_par
Max # iterations ff_nitmax
Minimum Significance ff_min_sigma
Minimum Separation ff_minsep
Convergence Limit ff_ftol
Show Progress ff_testplot
Show progress/cancel bar ff_progress_bar


Last updated 07 November, 2008 by Kim Tolbert , 301-286-3965