What is difference between "RGB to CIELAB" and "Lab Stack"

At first

Hi,

I try to get “Lab values” from Image.

I think there is two way to get “Lab values”

The first one does Image > Type > Lab Stack, the second one does Color > RGB to CIELAB

What is the difference between the two?
The images and measurement results for each channel (Lab) are different.

Sample image and/or code

I downlode this picture from here
clown

RGB to CIE LAB ver



Lab Stack ver



Each picture in each channel is not the same, Why is this so?

Thanks!

Maybe you can find some hints in the code.
Check the implementations …

I) … for the ImageJ type conversion ‘Image>Type>Lab Stack’ : ColorSpaceConverter.java

This function assumes sRGB input:
The RGB to L*a*b* conversion assumes sRGB for conversion to XYZ but then uses the specified white point to convert from XYZ to L*a*b*.
see Color Space Converter info

II) …for FIJI type conversion (Color > RGB to CIELAB) : CIELAB.java

Compare the transformation parameters and the gamma conversion of all conversion steps.

Maybe there is a difference between both implementations
or
one of the commands automatically converts the RGB to sRGB data before converting to CIELab.

2 Likes

Sorry for late reply.
I try to read this codes.

I thought it was affected by the illuminant light source, but probably not.
As you said, I think it’s affected by RGB, or bit shift operations, etc.

I’ll post back when I get this sorted out!
Thank you very much.