Image Degradation by Zeroing Block DCT vs. Full DCT Coefficients
Shuyi Ying, Ruihan Yin · 2020
As Discrete Cosine Transform (DCT) has been applied widely in image processing, it has been extensively studied in recent years. It is an interesting research topic to reveal the processing effect of block DCT and full DCT on the same image. In this paper, it is found that the block size of DCT is directly related to the impact of different DCT coefficients on an original image. To be more specific, keeping the proportion of zero coefficients unvaried, the distortion level of the image increases as the DCT block size decreases, appearing more and more uneven ripples. In contrast, the same operation by full DCT causes less distortion to the image. Additionally, with a constant block size, a larger percentage of zero coefficients results in a greater distortion. For the above results, this paper studies further about the mathematical relationship between PSNR value and the percentage of zeroing DCT coefficients.