1. A method comprising: receiving, at a computer system, a digital image comprising image values “I” corresponding to a plurality of pixels, where each image value I j comprises [red (R j ), green (G j ), blue (B j )] T associated with a corresponding pixel “j” of the plurality of pixels, j=1. .. M, the digital image having a colour bias due to illumination conditions when the digital image was acquired, the colour bias representing an illuminant “w” of the digital image; accessing by the computer system, a plurality of predetermined illuminants w k =[R k , G k , B k ] T , k=2, 3,. .. on a storage device associated with the computer system, each of the accessed plurality of predetermined illuminants w k being associated with a corresponding one of predefined illumination conditions; for each predetermined illuminant w k of the accessed plurality of predetermined illuminants, estimating, by the computer system, a p-norm distance X k between the predetermined illuminant w k and the image values “I” of the received digital image, where the p-norm is a constrained Minkowski norm having a finite p that is larger than 1, X k = { ∑ t = 1 B ⁢ ⁢ ∑ f = 1 M ⁢ ⁢  W kt - L f ⁢ ⁢ t  p M } 1 / p ; selecting, by the computer system, a predetermined illuminant w 0 from among the accessed plurality of predetermined illuminants that corresponds to the smallest p-norm distance X 0 from among the plurality of estimated p-norm distances, X 0 = min k ⁢ ⁢ X k = { ∑ t = 1 B ⁢ ⁢ ∑ f = 1 M ⁢ ⁢  W 0 ⁢ t - L f ⁢ ⁢ t  p M } 1 / p ; and assigning, by the computer system, the selected predetermined illuminant w 0 as the illuminant associated with the received digital image, w:=w 0 .