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The ENVI-format is an open file format commonly used to store hyperspectral imaging data. The format consists of two files, a header file and a buffer file.
This ASCII file ('.hdr') works as the descriptor for the buffer file. It contains the information on how to interpret the buffer file. This Meta Data is structured in fields, each having an ID, a name and a value. The ID is used to access a field. The name is a string as defined in the ENVI-format.
The following list contains a number of notable fields:
•Interleaved type:
To interpret the image as a hyperspectral image cube it is necessary to know which axis in the image is the spectral axis.
The field Interleave contains this information:
BandInterleavedByLine [x, y, z] → [samples, bands, lines]
BandSequential [x, y, z] → [samples, lines, bands]
BandInterleavedByPixel [x, y, z] → [bands, samples, lines]
•Samples:
Number of samples. When using pushbroom cameras this dimension defines the spatial axis of the image at a given time
•Lines:
Number of lines. When using pushbroom cameras this dimension defines the timeline axis
•Bands:
Number of bands.
•Wavelength: (optional)
Array of double values. The unit is given in the field WavesUnit
•Wavelength Unit: (optional)
Unit of Wavelength
•FWHM: (optional):
Full-width-half-maximum
This file contains the image as binary data with the extension '.bin'. The information on how to parse this data is given in the header file.