Color image enhancement by scaling the discrete wavelet transform coefficients

This paper presents a performance based comparison of some of the major compressed domain color image enhancement techniques with special emphasis on the Color Enhancement By Scaling the DCT Coefficients technique [CES-DCT] and Color Enhancement By Scaling the Wavelet Transform Coefficients technique [CES-DWT]. The CES technique is found to be simple but more effective than some of the existing enhancement techniques suggested earlier. The novelty of the CES technique is that it treats the chromatic components, while previous techniques treated only the luminance component. The CES-DWT utilizes the advantages of the wavelet transform and is found to be capable of improving both global and local contrast as well as preserving color consistency. The results of all previous compressed domain enhancement techniques along with that of the CES are compared with respect to those obtained by applying a spatial domain color enhancement technique that provides very good enhancement. The CES-DWT technique is found to provide better enhancement compared to other compressed domain based approaches (even better than CES-DCT) and is computationally more efficient than the spatial domain based method.