Add support for EDAX line scan data

[AndrewHerzing]

Describe the functionality you would like to see.

The EDAX reader can read .spd files which are the output from a 2D EDS mapping acquisition. It cannot currently read the .lsd file format which results from a 1D EDS line scan acquisition. Support for this format would be very nice to have.

Describe the context

The EDAX reader supports the .spd file format which is the output format for EDS maps acquired in TEAM (and potentially other EDAX software products). When line scan data is collected, the data is stored in .lsd files which have the same format as .spd files and the same relationship to the associated .spc file. So, if one just changes the file extension from .lsd to .spd, the data can be read with the existing reader.

The only thing missing is the spatial coordinates and calibration for the scan. With .spd files, this can be read from an associated .ipr file, but this not produced with line scan data. Instead, a .csv file is saved along with the .lsd file. The .csv file contains a 14 line header with some experimental metadata along with columns associated the line scan. These columns are labeled in row 15 and contain the following information:

• Point : a linear index of scan points from 1 to nSpectra from the spd header
• Distance : Calibrated spatial index (units: nm)
• Xray line (e.g. 'Fe K') : Spectral intensity along the scan. There is one column each for each line selected in the TEAM software.
• Image : STEM image detector intensity along the scan
• Frame : The number of scans over the line that were acquired. This integer is just repeated nSpectra times

So, it would appear to be fairly straightforward to simply add .lsd as an accepted extension for this reader and then treat the .lsd file as any other .spd file would be. Then parse the CSV file to get the calibrated probe position for the xaxis of the resulting Signal. Reading the simultaneous STEM detector intensity (Image column) would also be very useful.

Unfortunately, the exact coordinates of the line scan with respect to the field of view (stored in a separate fovXXXXXXXXX.bmp file) do not appear to be exported.

Additional information

I can add example files for testing at some point.

[ericpre]

Yes, this sounds good. A small test files will be needed, see this guidance on making test file: https://hyperspy.org/rosettasciio/contributing.html#making-test-data-files

[ericpre]

Would you be able to share the information as it is the case for spd, spc and ipr files? See https://hyperspy.org/rosettasciio/file_specification/index.html#edax