To resolve the problem of mosaicing in portable cameras,a color difference space demosaicing algorithm based on all phase DCT/IDCT filters was presented.According to the correlation between the three color planes of color image and their sampling grids type,all phase diamond halfband IDCT filter was used to reconstruct the green image,and all phase extended DCT interpolation filter was used to reconstruct the R-G and B-G images.All phase IDCT interpolation filter was a pure 2-D filter which could convert between quincunx sampling grid and square sampling grid directly,while all phase extended DCT interpolation filter could restrain the Gibbs effect of FIR filters.Experimental results show that the Peak Signal-to-noise Ratio(PSNR) of reconstructed images outperform that of bilinear interpolation up to 6dB.And the proposed method can preserve more image edge details and has higher computational efficiency than other adaptive methods.