Extracting illumination from images by using the wavelet transform

We present an efficient way to extract the illumination from the images by exploring only the low frequencies into them jointly with the use of the illumination model from the homomorphic filter. This illumination information may be used to code images in a sequence with only illumination changes. We take an image from the sequence as a reference. Any other image to be coded is approximated by changing the low pass band of the discrete wavelet transform of the reference with that from the image to be coded. To improve the recovering process it is possible to modify the high frequencies into the reference image according to the differences between the illumination from the reference and from the image to be recovered. The results obtained show us a new way to code illumination changes when used with video sequences.