Why yet antother image file format?

Since the inception of digital imaging some decades ago, an almost uncountable number of conventional image file formats has been defined. What is still lacking is a standardised image file format for spectral image data.

Definition

For the purposes of this discussion, we assume the term spectral image file format to refer to image file formats that store spectral data for each pixel, as opposed to the far more common colour values. Generally, spectral data consists of measurements of physical quantities (the intensity of electromagnetic radiation), measured in physical units without any regard for what the human visual system can discern, while colour values (the quantification of a visual sensation, usually as a function of some basis colours like e.g. red, green and blue) are intrinsically limited to what humans can actually see. The spectral data which is stored for each pixel is more specifically the intensity of electromagnetic radiation {\em per wavelength}, so that one can reconstruct a visual sensation from it. This can be done since the relationship between spectra as a visual stimulus and their corresponding colour sensations is well understood.

Scope

In contrast to "normal" image formats, the contents of a spectral image need not be something that human vision can directly perceive at all. The human eye is only sensitive to wavelengths between (at the utmost) 380 and 830 nanometers; if one wants to visualise other wavelengths one has to resort to false colour techniques of some kind.

The more obvious candidates that will have use for such a format are natural sciences like geology (remote sensing), astronomy (multispectral imaging), and of course computer graphics (especially for correct texture mapping in spectral rendering and tone mapping approaches).

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This page is maintained by Alexander Wilkie. It was last updated on February 7, 1999.
If you have any comments, please send a message to wilkie@cg.tuwien.ac.at.