Posted by
Marcel Tschudin on
Jan 28, 2015; 12:03pm
URL: http://imagej.273.s1.nabble.com/Measuring-Dominant-Wavelength-tp5011335p5011347.html
Thanks to all of you for all your various comments. I only was wondering
whether I could extract additional information from the colours in a large
collection of photos which have not been made for this specific purpose.
The links provided by Jean-Louis show that some researchers appear to
convert RGB to wavelength with certain restrictions. It looks however like
none of their solutions became a general applicable tool in ImageJ (or
another photo program?).
Regards,
Marcel
On Wed, Jan 28, 2015 at 11:37 AM, Gabriel Landini <
[hidden email]>
wrote:
> On Tuesday 27 Jan 2015 19:31:27 Greg <
[hidden email]> wrote:
> > Probably the best you can do without a spectrometer would be to convert
> > the color space of your image to a cylindrical one such as HSV and use
> > the H (Hue) value to get an approximation of the dominant color (not
> > wavelength). Alternatively, you might get better results with a simple
> > diffraction grating spectrometer in front of the camera ala the public
> > lab spectrometer.
>
> Hm... not in HSV space derived from RGB images...
> E.g. "Yellow pixels" could be proper "yellow light", or the "sum or red and
> green light". You can't reach any conclusions with HSV.
>
> If you want to do this properly, with images, you could use a calibrated
> greyscale camera and a bank of narrow band pass filters or one of those
> fancy
> "tunable filters" like the Varispec system.
>
> Cheers
>
> Gabriel
>
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