Transform coding using the discrete cosine transform is one of the most popular techniques for image and video compression. However, at low bit rates, the coded images suffer from severe visual distortions. An innovative approach is proposed that deals with artifacts in JPEG compressed images. Our algorithm addresses all three types of artifacts which are prevalent in JPEG images: blocking, and for edges blurring, and aliasing. We enhance the quality of the image via two stages. First, we remove blocking artifacts via boundary smoothing and guided filtering. Then, we reduce blurring and aliasing around the edges via a local edge-regeneration stage. We compared the proposed algorithm with other modern JPEG artifact-removal algorithms. The results demonstrate that the proposed approach is competitive, and can in many cases outperform, competing algorithms.

https://www.spiedigitallibrary.org/journals/Journal-of-Electronic-Imaging/volume-23/issue-1/013018/Algorithm-for-JPEG-artifact-reduction-via-local-edge-regeneration/10.1117/1.JEI.23.1.013018.pdf

Algorithm for JPEG artifact reduction via local edge regeneration

There is disclosed an apparatus, a method and a computer program for video coding. The apparatus comprises a selector configured for selecting a pixel for prediction; a projection definer configured for determining a projection of said pixel to a set of reference pixels; and a prediction definer configured for selecting one or more reference pixels from said set of reference pixels on the basis of said projection, and using said selected one or more reference pixels to obtain a prediction value for said pixel to be predicted.

An apparatus, a method and a computer program for video coding

No-reference analysis of decoded MPEG images for PSNR estimation and post-processing

In one example, a method for encoding video data includes determining a first value for a line of a first plurality of lines, wherein the first plurality of lines are perpendicular to a first edge of a block of the video data; in response to determining that the value satisfies at least one threshold: determining a second value for the line of the first plurality of lines; and determining a second value for a line of a second plurality of lines, wherein the second plurality of lines are perpendicular to a second edge of the block of video data; determining, based on the second value for the line of the first plurality of lines and the second value for the line of the second plurality of lines, an average value; and determining, based on the average value, whether or not to encode one or more deblocking parameter offsets.

Blockiness metric for large hevc block artifacts

Image compression plays a pivotal role in minimizing the data size and reduction in transmission costs. Many coding techniques have been developed, but the most effective is the JPEG compression. However, the reconstructed images from JPEG compression produce noticeable image degradations near block boundaries called blocking artifacts, particularly in highly compressed images. A method to detect and reduce these artifacts without smoothing images and without removing perceptual features has been presented in this paper. In this work, a low computational deblocking filter with four modes is proposed, including three frequency-related modes (smooth, non-smooth, and intermediate) and a corner mode for the corner of four blocks. Extensive experiments and comparison with other deblocking methods have been conducted on the basis of PSNR, MSSIM, SF, and MOS to justify the effectiveness of the proposed method. The proposed algorithm keeps the computation lower and achieves better detail preservation and artifact removal performance.

Detection method and filters for blocking effect reduction of highly compressed images

Design a deblocking filter with three separate modes in DCT-based coding

The enlargement method is a partial technology in many application including medical imaging, satellite imaging, and video applications. Due to the wavelet representation has characteristics of the efficient time-frequency localization and the multi-resolution analysis, the wavelet transforms are suitable for processing the image resolution enhancement. Therefore, this method focuses on wavelet-based image resolution enhancement and proposes a framework of enlargement method. This proposed method is based on the estimation of detail wavelet coefficients at high resolution scales. The method exploits shape function according to wavelet coefficient correlation in a local neighborhood and employs undecimated discrete wavelet transform to estimate the unknown detail coefficients. The simulation results objectivity show that the proposed method is considerably superior to conventional image interpolation techniques.

An Enlargement Method Using Undecimated Wavelet Transform and Shape Function

Due to the bandwidth and storage limitations, image must be compressed before transmission. The set partitioning in hierarchical trees (SPIHT) algorithm is an efficient method for lossy and lossless coding of image. This paper presents some modifications on the set partitioning in hierarchical trees (SPIHT) algorithm. It is based on the idea of insignificant correlation of wavelet coefficient among the medium and high frequency subbands respectively. In this scheme, insignificant wavelet coefficients that correspond to the same spatial location in the medium subbands can be used to reduce the redundancy by a combined function that modified SPIHT proposes. In the high frequency subbands, the modified SPIHT proposes dictator to reduce the interband redundancy. Experimental results show that the proposed technique improves the quality of the reconstructed image in both PSNR and perceptual result when compare to JPEG2000 at the same bit rate.

Wen-Chien Yen

Papers

Design a deblocking filter with three separate modes in DCT-based coding

An Enlargement Method Using Undecimated Wavelet Transform and Shape Function

Natural image compression based on modified SPIHT