Glossary
Lossless
Lossless means the image data comes out bit-for-bit identical to what went in.
Updated
For metadata removal, lossless means the compressed image data is copied through without being decoded. Nothing is recompressed, so nothing degrades — the output pixels are identical to the input pixels, verifiably so.
This is achievable precisely because metadata lives in the container rather than in the compressed data. There is no technical reason removal should cost quality; tools that make it cost quality are choosing an easier implementation.
The claim is testable. Decode the original and the result and compare them pixel by pixel — identical output is the whole of the claim. The engineering write-up covers how each container is handled and how results are verified.
Related terms
- Re-encoding — Re-encoding is decoding an image and compressing it again, which discards detail on every pass through a lossy format.
- Container format — A container format is the file structure that wraps compressed image or video data together with the metadata describing it.
- Chunk — A chunk is a self-describing section of a file, carrying its own type label and length.