Color Space Conversions

New in version 0.9.6.

Red-green-blue images

An RGB image is represented as a 3-dimensional array of shape (h,w,3), where each pixel is represented by three values, red/green/blue.

For example, the classic lena image is a (512,512,3) array:

import mahotas as mh
lena = mh.demos.load('lena')
print(lena.shape)

We can convert it to greyscale as using rgb2grey (or rgb2gray if you prefer, both work). This conversion uses a visually realistic method (which weighs the green channel more heavily as human eyes are more sensitive to it). For example:

import mahotas as mh
lena = mh.demos.load('lena')
lenag = mh.colors.rgb2grey(lena)

from pylab import imshow
import mahotas as mh
lena = mh.demos.load('lena')
lenag = mh.colors.rgb2grey(lena)

imshow(lenag)

(Source code, png, hires.png, pdf)

_images/color-1.png

We can also convert to sepia with rgb2sepia:

lenas = mh.colors.rgb2sepia(lena)

from pylab import imshow
import mahotas as mh
lena = mh.demos.load('lena')

lenas = mh.colors.rgb2sepia(lena)

imshow(lenas)

(Source code, png, hires.png, pdf)

_images/color-2.png

Other Colour Spaces

Mahotas can also convert to XYZ space and to the Lab space with rgb2xyz and rgb2lab, respectively.