Re: Colorimetric Parameters
Posted by
Michael Schmid on
Feb 20, 2015; 9:50am
URL: http://imagej.273.s1.nabble.com/Colorimetric-Parameters-tp5011588p5011705.html
Hi Rita,
the various Lab plugins use different scale for the output. E.g. if the output is 8 bits, it is usual to map the 0-100 range of L to the full 0-255 range of an 8-bit image, for better accuracy. The a and b values are typically mapped to 8 bits such that 128 corresponds to 0.
The Color Space Converter
http://rsb.info.nih.gov/ij/plugins/color-space-converter.htmlcreates floating-point output output if you select 'separate iages', so it's output is already in the 0-100 range for L and +/-100 range for a, b.
Michael
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On Feb 19, 2015, at 17:59, Rita Goncalves wrote:
> Hello Michael,
>
> Thank you very much for your answer and advices.
>
> However, i'm still having problems with it. I've made the download of all plugins you mentioned.
>
> As I told before, we are studying the color of fruits. Imagine that I have a picture of a pear and it appears in RGB color type. When I go to the Threshold Color, I adjust the brightness in order to obtain the pear in black and the rest of the picture in white. In the Threshold Color window, it appears the values of Hue, Saturation and Brightness or the values of L*, a* and b*, for example.
>
> First of all, I don't understand this values because L* varies from 0 to 100, and in the Threshold window appears values from 0 to 255.
>
> What I am trying to understand is if there is any plugin that can analyze an image and give me the exact value of L*, a* and b*.
>
> The plugins you showed me don't give this value that I want or probably I am doing some mistake.
>
> Again, thank you very much.
>
> Rita
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