2007.01.18 11:27 "Re: [Tiff] Scientific Data in Tiff images", by Andrey Kiselev
On Wed, Jan 17, 2007 at 10:40:10PM -0700, Richard Nolde wrote:
In that application, the original data would have no meaning to anyone but a spectrometer in raw form. Digital Elevation Model data can be negative but at least it is linear. It is my opinion that it is wrong to assume that you can auto scale any scientific data and not do an injustice to the result in at least some special area of scientific application. Set values for SMinSampleValue and SMaxSampleValue for the agreed upon logical min/max in that scientific field, not the specific image in question. If you are using TIFF as a scientific data interchange format instead of a picture viewer format, then the people in each field need to get together and decide what the logical range of values in the data set is going to be, not the TIFF community who can't possibly know these things. If you just want TIFF to show a representation of the data for general viewing and passing amongst desktop applications, then pick a set of minima/maxima that lend themselves to viewing and printing, scale your data to those values and be done with it. Having long double floating point numbers in a TIFF file won't do you any good if all the values are zero except for one pixel that has a value of 2**38 - 1 if your intention is to view the image on screen without your own custom software.
I am totally agree with all above.
I would vote for adding new TAGS to provide the additional information that explains how the stored image data relates to the original collected range, ie scale factor, and the range of possible values for that data. You really need both for scientific data. If there are standard algorithms that are applied to the data that can be identified in a TAG, add them too.
I just want to add that process of new that tags addition is out of scope in this list, it should be leaved to those communities who work in those particular areas. They are only know what kind of additional information needed for their data.
But what we can really do as libtiff developers is improvement in custom IFD support which should greatly help to store any kind of additional information in single TIFF file.
Andrey V. Kiselev