Choosing the Best Lossless Compression Algorithm for Grayscale Images

The choice of the best lossless compression algorithm for grayscale images can vary based on the specific characteristics of the images and the requirements of the application. While some compression algorithms like PNG and TIFF are widely used, newer options like WebP and FLIF are also providing better compression ratios for some scenarios.

Commonly Recommended Lossless Compression Algorithms

PNG - Portable Network Graphics

DEFLATE Compression: PNG uses DEFLATE compression, which is a combination of LZ77 and Huffman coding. This makes PNG particularly well-suited for images with large areas of uniform color or simple patterns, making it a popular choice for grayscale images due to its balance between compression efficiency and image quality. PNG supports interlacing, multiple images, and transparency, which adds to its flexibility.

TIFF - Tagged Image File Format

Variety of Compression Methods: TIFF supports various compression methods such as LZW (Lempel-Ziv-Welch) and ZIP. TIFF with LZW compression is often used for high-quality grayscale images in professional settings. LZW is known for its high compression efficiency and compatibility across different systems. However, LZW has been patented and its usage may vary based on licensing restrictions.

WebP

Flexible Compression: While primarily known for lossy compression, WebP also supports lossless compression. It can provide better compression ratios than PNG in some cases, although platform support may vary. WebP's flexibility allows it to be used in different contexts, including optimizing web delivery.

FLIF - Free Lossless Image Format

Excellent Compression Ratios: FLIF is a newer format that offers excellent compression ratios for lossless compression and outperforms PNG in many scenarios. FLIF is designed to be more efficient and offers better performance than traditional lossless algorithms, making it a compelling choice for certain applications.

JPEG 2000

Multiple Compression Options: JPEG 2000 provides both lossy and lossless compression options. It offers good compression ratios for grayscale images and is used in various professional applications. The high-quality compression and flexibility of JPEG 2000 make it a reliable choice for many use cases.

BPG - Better Portable Graphics

Outperforming JPEG and PNG: BPG is designed to outperform JPEG and PNG and can handle lossless compression effectively. This makes it a strong contender for users who need high-quality compression without losing any image data.

Conclusion

For general use, PNG is often the best choice due to its wide support and balance between compression efficiency and image quality. For specialized applications or environments, TIFF or FLIF may be more suitable. Ultimately, the choice may depend on the specific use case such as the need for compatibility, compression ratio, and processing speed.

It's worth noting that most image compression formats do not take advantage of inter-color correlation, treating each color plane independently. In the case of grayscale images, this means that the benefits of grayscale are not utilized in terms of compression. For bi-level images, JBIG2 could be an excellent candidate. For grayscale, three good candidates are:

tJPEG 2000: Provides good compression ratios and is used in various professional applications. tAVC Intra Lossless: Known for its high-quality lossless compression. tHEVC Intra Lossless: Generally considered the best for lossless compression but may require specific decoders.

HEVC Intra lossless is probably the best, but finding suitable decoders might be challenging.