A new approach of watermarking adaptively in DC coefficients of color images is presented. The proposed algorithm uses two AC coefficients of DCT blocks to classify the pixel blocks into three different types

namely

smoothed

edged

and texture block. The strength of watermark is set adaptively according to the pixel block type. Four subimages from the original color image can be obtained with downsampling. These subimages are highly correlated. Take into consideration the correlationship.One bit watermark is embedded，in two DC coefficients which is selected from the subimages. The selection of DC coefficients is based on Keycontrolled random numbers so as to disperse the energy of watermark and win secure watermarking. Blind extraction of watermark can be performed directly on pixel domain. Whilst the watermark is inserted into both the luminance component in YIQ model and the blue channel in RGB model

and examine and compare their performances. Extensive experimental results demonstrate that the algorithm achieves the high robustness and good quality of watermarked image

and the performance of watermarking in Y component outperforms that of B component.