Most lossy image compression systems use a transform that does not reduce the data size but makes transformed data that is more compressible. This means the fi

Most lossy image compression systems use a transform that does not reduce the data size but makes transformed data that is more compressible. This means the final layer of compression is a traditional compressor. These, like the transforms themselves get improved upon over time. JPEG is old. When I did some experiments with various compression techniques, I found that DCT with a LZMA base compared quite well to newer compression systems.