Reduction of Artefacts in JPEG-XR Compressed Images

Area of Science:

• Digital Image Processing
• Image Compression Standards

Background:

• JPEG-XR encoding uses Photo Overlap Transform (POT) and Photo Core Transform (PCT).
• Microsoft's Device Porting Kit (DPK) was used for JPEG XR image encoding/decoding.
• Lossy compression with quantization parameter >1 in JPEG-XR leads to checkerboard, border, and corner artefacts.

Purpose of the Study:

• Analyze the cause of artefacts in JPEG-XR lossy compression.
• Propose a solution to mitigate these visual artefacts.
• Improve the image quality of JPEG-XR lossy encoding.

Main Methods:

• Investigated artefact generation in JPEG-XR using Microsoft's DPK.
• Identified POT and quantization as primary sources of artefacts.
• Introduced a "uniform matrix" multiplication step post-POT and pre-inverse POT.

Main Results:

• The uniform matrix method effectively reduces checkerboard, border, and corner artefacts.
• Image quality in lossy JPEG-XR encoding is improved.
• No increase in calculation complexity or file size was observed.

Conclusions:

• The nonlinearity of POT and quantization in JPEG-XR causes visible artefacts.
• The proposed uniform matrix method offers an effective and simple solution.
• This technique enhances JPEG-XR image quality for applications sensitive to artefacts.