Worked on the koreader/koreader repository to deliver enhancements to the PDF rendering pipeline, focusing on improving readability and performance for end users. Leveraged Lua and front end development skills to implement SMask isolation with background cleanup, which addressed contrast issues and optimized rendering speed. Introduced a white-threshold rendering feature that adapts document display for varying backgrounds, making content more accessible across different devices. Maintained clear traceability by linking changes to relevant issues, supporting quality assurance and release processes. The work demonstrated a targeted approach to feature development, addressing specific user needs in PDF rendering without introducing new bug fixes during the period.