`skimage.color.colorconv:lab2lch`

source: /_skimage2/color/colorconv.py:1810

Signature

def lab2lch(lab, *, channel_axis = -1)

Convert image in CIE-LAB to CIE-LCh color space.

CIE-LCh is the cylindrical representation of the CIE-LAB (Cartesian) color space.

lab : array_like of shape (..., C=3, ...): The input image in CIE-LAB color space. Unless channel_axis is set, the final dimension denotes the CIE-LAB channels. The L* values range from 0 to 100; the a* and b* values range from -128 to 127.
channel_axis : int, optional: This parameter indicates which axis of the array corresponds to channels.
versionadded 0.19
channel_axis was added in 0.19.

out : ndarray of shape (..., C=3, ...): The image in CIE-LCh color space, of same shape as input.

: ValueError: If lab does not have at least 3 channels (i.e., L*, a*, and b*).

The h channel (i.e., hue) is expressed as an angle in range (0, 2*pi).

from skimage import data
from skimage.color import rgb2lab, lab2lch
img = data.astronaut()
img_lab = rgb2lab(img)
img_lch = lab2lch(img_lab)

✓