The Frame widget serves for detailed visualization of spectral cubes in both spectral and spatial direction. Its primary use is in live acquisition mode for line-scan applications.


In this setup, it provides a logical view of the data transferred from a camera i.e. spectral frames. Each frame provides spectral responses for a line of spatial pixels. The Frame widget is useful during data acquisition as it helps us to understand camera focus, visually judge scan borders, dead pixels or other artifacts.


It is also enabled for introspection of already loaded spectral cubes. Note the important conceptual difference that in live acquisition mode, the frame widget shows raw spectral frames being acquired, while in the off-line mode it visualizes content of the current cube that is typically already corrected into reflectance.


In the following screenshot, the frame widget shows one spectral frame from a loaded image. The area shows the frame content. The spatial pixels are provided horizontally, the spectral information is displayed vertically.

The colored lines in the frame widget are then further visualized in the spectral plot and spatial plot. The corresponding band and pixel indices are located on the top of the frame panel.



The context menu on the plots exposes number of options:

  • Switching between default dark and white background. White background may be beneficial when using the spatial profile plot to judge camera focus on a structured pattern.
  • Several options for plot scaling. The Auto scale provides automatic stretch based on the data from. The Set range from... options allow the user to set the range from the project, the acquisition max raw display value, or the camera saturation value (if available).
  • The plots can be copied to clipboard as an image.


Focus assist

When setting the focus for the camera, it is useful to view the frame image to see how sharp the lines are. This will often require that the display range is changed to get better contrast over the full frame. Only changing it too much may cause pixels to go out of range, which will make it more difficult to see:



The Focus assist option helps with this by scaling each separate band to achieve maximum contrast per band:



Now the focus is a lot easier to set and validate. Note that the display range is not used for this, so it can stay at the default or other preferred value.