learnjpeg-go

Learn JPEG in Go

Learn how JPEG works by reinventing the library. Focus will be on bare minimum amount of code and the workings of code are understandable.

Limitation (to speed up dev, learn and reduce complexity)

• Encode only
• Portable Pixmap Format P6 input file format only
• Quality set to 75%, no other quality
• No Chroma subsampling
• Width and Height are divisible by 16
• Only Lossy and Baseline sequential process
• No optimisation
• Use precomputed or provided numbers

Order

• Convert RGB to YCbCr
• Chroma Subsampling 4:2:0
• Pixels block to 8x8
• Discrete Cosine Transform (DCT II)
• Quantization
• Encode
  • Zigzag
  • Huffman
  • Run-length encoding
• Store Header + Data

References

• Wikipedia JPEG
• Wikipedia Netpbm
• JPEG File Interchange Format
• JPEG Header Information
• YCbCr
• Chroma subsampling
• Huffman Coding
• Run-length Encoding
• JPEG File Layout and Format
• Go JPEG library
• Colourspaces (JPEG Pt0)- Computerphile
• JPEG 'files' & Colour (JPEG Pt1)- Computerphile
• JPEG DCT, Discrete Cosine Transform (JPEG Pt2)- Computerphile
• ITU-T T.81
• JPEG File Interchange Format
• JPEG Standard
• Chapter 9 Image Compression Standards - Rutgers CS