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Steca: GUI overview

Main window

Most of work with Steca is done in a single main window. The window has the usual layout: a menu bar, a main working area with multiple panels, and a status bar.

main window

Dock widgets

The Files, Datasets, and Metadata panels are 'dock widgets'. They can be 'docked' to either side of the window, or even overlapped to save space, for example like so:

main window

The three dock widgets can be hidden or shown, by selecting the [View/Files], [View/Datasets], and [View/Metadata] menu options. [View/Reset] shows the dock widgets in their original place.

The main window menu is organized in several submenus.

A number of menu options are also available as tool buttons in the various panels of the main window. The same icons that are on the tool buttons are also shown in the menus, next to each respective menu text. Often used menu options have associated keyboard hotkeys, shown right next to the menu text.

The submenus are:


Add files… Opens a file selection dialog; adds selected data files to the session; load datasets (images and metadata) contained in the files.
Remove selected file(s) Removes files selected in the 'Files' panel and corresponding datasets from the session.
Enable correction file… Controls correction of detector pixel sensitivity. If a (vanadium) correction file has not been yet loaded, a file can be selected and image data loaded. Typically, a correction file contains only a single image; if there are more than one image in the file, they will be collapsed into one by averaging intensities of the corresponding pixels. The correction can be enabled and disabled (switched on and off) by repeatedly selecting this option.
Remove correction file Removes the correction file from the session.
Load session… Clears the current session and loads (restores) a saved session from a session file.
Save session… Saves the current session to a session file. If the file exists, it will be overwritten.
Quit Ends the program.


Files Shows or hides the Files panel.
Datasets Shows or hides the Datasets panel.
Metadata Shows or hides the Metadata panel.
FullScreen Switches the window to a full screen mode and back.
Statusbar Shows or hides the status bar. (The status bar is used to display warnings and error messages.)
Reset Resets the positions and visibility of all of the above to the initial state.


Rotate Rotates the images clockwise.
Mirror Mirrors the images.
Global intensity scale Displays images with an intensity (colour) scale normalized to the maximum intensity of all images; otherwise the intensity scale is normalized individually for each image.
Link cuts Make cuts on all sides equal.
Show overlay Shows a layer with additional information on top of the image.
Scale in steps Scale image to minimize pixel scaling artifacts.
Show gamma range Show the range of currently selected gamma slice.


Select regions Enables the tool that is used to select background and reflection regions.
Show fitted background Shows the background-fitted polynomial.
Clear background regions Removes all background regions.
Clear reflections Removes all reflections.
Add reflection Adds a new reflection to the reflections list.
Remove reflection Removes the selected reflection from the reflection list.
All datasets Shows the diffractogram of the combination of all selected datasets.
Global intensity scale Normalize the diffractogram intensity scale to the maximum intensity of all datasets; otherwise the intensity scale is normalized individually for each diffractogram.
Averaged intensities Experimental: Show (or output) intensities averaged in each 2θ bin; otherwise use their simple sum.


Pole figures… Opens a dialog for calculation, display, and output of pole figure data.
Diagrams… Opens a dialog for calculation, display, and output of diagram data.
Diffractograms… Opens a dialog for calculation, display, and output of diffractogram data.

See data output.


About & Configuration… Shows the 'About' dialog that also contains configuration options.
Online documentation… A link to these pages.
Check for update… Checks whether there is an updated Steca version available for download.


The content of the main window is divided into the following panels:

main window with panels


The 'Files' panel shows the list of loaded data files.

panel Files

Below the file list are these controls:

  • a button for adding files [also menu: File/Add files…],
  • a button for removing files [File/Remove selected files],
  • a box with the name of the correction file,
  • a button for loading a correction file and switching the correction on and off [File/Enable correction file…],
  • a button to remove the correction file [File/Remove correction file].

In the file list, one or more loaded files can be selected. All datasets contained in the selected files are shown in the 'Datasets' panel and included in calculations.


This panel contains a numbered list of datasets from files that are selected in the 'Files' panel. If there are any metadata items checked in the 'Metadata' panel, those are displayed in columns along the dataset numbers.


Datasets can be combined in groups of a specified number of datasets, by using the 'Combine:' number box. The 'Diffractogram' panel then displays the diffractogram of combined data.

Datasets - combined


This panel shows the metadata of the selected (single or combined) dataset. The checkboxes allow selected metadata item to be displayed in a column in the 'Datasets' list.


If datasets are combined:

  • the cummulative time and monitor count are the maxima of individual datasets
  • delta time and delta monitor count are summed
  • the rest of numerical metadata are averaged
  • text values are taken from the first dataset.

Options and Fitting

This panel has three tabs:

  • Geometry: sets the detector-related parameters
  • Background: controls the background correction
  • Reflections: controls the refkection fitting


Contains controls to set:


  • The detector-sample distance (typically around 1000 mm).
  • The size of a detector pixel (typically around 1 mm).
  • The beam offset: for X-ray detectors this is the offset of the beam centre. Set the values to 0 for neutron detectors.
  • Image transformation ( rotation and mirroring).
  • The image cut (to “cut off” – exclude from processing – the border detector regions with faulty pixels).
  • to link the four cut values

These options apply to all loaded datasets. Images should be transformed (rotated and mirrored) so that the direct beam is assumed to be to the left of the image, 2θ increasing left-to-right.



  • enables the tool for selecting background regions. Add selected background regions in the diffractogram panel with the primary (right) mouse button, remove them with the secondary (left) mouse button.
  • controls the visibility of the fitted background polynomial.
  • removes all background regions.
  • 'Pol. degree' : select the degree of background-fitted polynomial (0 - 4).

Hint: Checked 'all datasets' helps with selecting the background regions.


Contains a list box with a list of reflections.


  • adds a reflection to the list, removes it.
  • enables the tool for selection a reflection range (with the primary mouse button).

The combobox below the list of reflections selects the type of a new reflection, or changes the type of the selected one. The types are:

  • Raw: sums the intensities in 2θ bins of the selected region,
  • Gaussian: fits the peak in the selected region by the Gaussian function,
  • Lorentzian: fits the peak by the Lorentzian function,
  • PseudoVoigt1 (a combination of a Gaussian and a Lorentzian, sigma=gamma),
  • PseudoVoigt2 (a combination of a Gaussian and a Lorentzian, sigma and gamma have separate values).

Fitting is done by M. Lourakis' levmar library.

A rather naive algorithm provides levmar with initial guesses.

The number boxes show:

  • 'min' and 'max': the selected reflection range,
  • 'guess x', 'y', 'fwhm': the guessed peak position, height, and width,
  • 'fit x', 'y', 'fwhm': the fitted peak position, height, and width.


Contains two tabs: the image from the selected dataset, and the correction file image (if any).

The controls (left-to-right):

panel Image

  • To switch on a global image intensity scale.
  • To scale the image in steps.
  • To display the cut and beam centre as an overlay over the image.
  • A number box that selects which image from combined datasets (if combined) is shown.
  • To switch on an overlay that shows the area of a selected gamma slice.
  • The number of gamma slices. 0 - no slicing is done.
  • A number box to select a gamma slice.
  • Two number boxes that show the range (min - max) of the selected gamma slice.


Shows the diffractogram - histogram of the selected dataset and selected gamma slice.


The controls:

  • Applied intensity normalization: none, monitor (count), Δ monitor (count), Δ time, background.
  • 'averaged intensities' : (experimental): if selected, the intensities (neutron counts in each detector pixel) in each 2θ histogram bin are averaged; otherwise they are simply summed. This setting also affects the pole figure and diffractogram outputs.
  • 'all datasets' : the diffractogram shows a combined histogram of all datasets.
  • 'fixed intensity scale' : temporarily prevents the intensity axis from readjusting.

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