Adaptive colour constancy algorithm using discrete wavelet transform

The colours of chromatically homogeneous object surfaces measured by a sensor vary with the illuminant colour used to illuminate the objects. In contrast, colour constancy enables humans to identify the true colours of the surfaces under varying illumination. This paper proposes an adaptive colour constancy algorithm which estimates the illuminant colour from wavelet coefficients at each scale of the decomposition by discrete wavelet transform of the input image. The angular error between the estimated illuminant colours in consecutive scales are used to determine the optimum scale for the best estimate of the true illuminant colour. The estimated illuminant colour is then used to modify the approximation subbands of the image so as to generate the illuminant-colour corrected image via inverse discrete wavelet transform. The experiments show that the colour constancy results generated by the proposed algorithm are comparable or better than those of the state-of-the-art colour constancy algorithms that use low-level image features.

► Adaptive colour constancy is achieved using multiscale data analysis through discrete wavelet transform.
► Optimum scale is automatically obtained from mutual relations between consecutive scales.
► Wavelet coefficients are used to estimate illuminant colour.
► Estimated illuminant colour is used to modify approximation subbands at the final level of the decomposition.
► The modified transform coefficients are used to reconstruct illuminant free image.