CIELAB color range for Scikit-image?

Question

I am working on CIELAB colour space but cannot find any information about the range of each channel produced by skimage.color.rgb2lab .

Thanks.

Answer 1

Just would like to post the answer from @Stefan

L: 0 to 100, a: -127 to 128, b: -128 to 127.

Answer 2

Quote from wiki, https://en.wikipedia.org/wiki/CIELAB_color_space

The scaling and limits of the a* and b* axes will depend on the specific implementation, as described below, but they often run in the range of ±100 or −128 to +127 (signed 8-bit integer).

In skimage, xxx2lab() usually return a float point array, thus it is more likely that the range of a* and b* is [-100,100].

PS:

I have tried image with value > 100 or < -100 in lab color, and I think the warnings I got from lab2rgb() in skimage could prove this point.

UserWarning: Color data out of range: Z < 0 in 30 pixels return xyz2rgb(lab2xyz(lab, illuminant, observer))