Environment

• Tested on: macOS Sonoma 14.0
• Ubuntu 22.04

Java SDK version

• Openjdk 21.0.1(macOS Sonoma 14.0)
• Openjdk 11.0.20.1(Ubuntu 22.04)

Decoding time

macOS Sonoma 14.0

• teatime.jpg: 0.32s
• monalisa.jpg: 0.20s
• gig-sn01.jpg: 0.41s
• gig-sn08.jpg: 0.52s

Ubuntu 22.04

• teatime.jpg: 0.25s
• monalisa.jpg: 0.14s
• gig-sn01.jpg: 0.31s
• gig-sn08.jpg: 0.35s

Note: time CLI command is used for statistics and the decoding time is averaged over 10 runs respectively

Some improvement

• IDCT can be speed up in certain ways because I precalculate the coefficients that are used (see lines 238–252).

Execution Guidelines

• To build executable and decode four images

$ make

• To build and decode four images and show all decoded images(prerequisite: open CLI program is installed or configured)

$ make open

• To build executable

$ make build

• To build executable and decode teatime.jpg

$ make tea

• To build executable and decode monalisa.jpg

$ make mona

• To build executable and decode gig-sn01.jpg

$ make gig01

• To build executable and decode gig-sn08.jpg

$ make gig08

• To clear all artifacts

$ make clean

• To run executable without using Makefile (prerequisite: at least make build is run before)

$ java Main image_filename  # e.g., java Main teatime.jpg