A Novel Psychovisual Threshold on Large DCT for Image Compression

Abstract

A psychovisual experiment prescribes the quantization values in image compression. The quantization process is used as a threshold of the human visual system tolerance to reduce the amount of encoded transform coefficients. It is very challenging to generate an optimal quantization value based on the contribution of the transform coefficient at each frequency order. The psychovisual threshold represents the sensitivity of the human visual perception at each frequency order to the image reconstruction. An ideal contribution of the transform at each frequency order will be the primitive of the psychovisual threshold in image compression. This research study proposes a psychovisual threshold on the large discrete cosine transform (DCT) image block which will be used to automatically generate the much needed quantization tables. The proposed psychovisual threshold will be used to prescribe the quantization values at each frequency order. The psychovisual threshold on the large image block provides significant improvement in the quality of output images. The experimental results on large quantization tables from psychovisual threshold produce largely free artifacts in the visual output image. Besides, the experimental results show that the concept of psychovisual threshold produces better quality image at the higher compression rate than JPEG image compression.

Tchebichef image watermarking along the edge using YCoCg-R color space for copyright protection

“…Most of watermarking schemes are performed using YUV, RGB [6], and YCbCr color spaces [7]. YCbCr has been widely used in image compression [8]- [11], this color space is able to achieve a good decorelation of the color image. Selecting color space in digital watermarking is an important element when we implemented on the color image.…”

Robust Image Watermarking Based on Psychovisual Threshold

“…According to Figures 1 and 2, the area under the psychovisual error threshold has potential resistance against JPEG quantization tables in image compression. In previous works, the psychovisual threshold has been applied to several image processing applications, such as image compression [14][15][16][17][18][19], adaptive image compression [20,21] and image watermarking [12].…”