How to use it
- Drop in JPEG 2000 files.
- Each is decoded and saved as PNG.
- Download the PNGs.
Lossless in, lossless out
Archives often store their masters as lossless JPEG 2000, a format with no loss at all. Converting to PNG keeps that: the decoded pixels are written exactly. That makes PNG the right target for scans of documents, maps and artworks you intend to study, crop or print.
High bit depth
JPEG 2000 can hold 12 or 16 bits per channel, common in medical and scientific imagery. Those are scaled to 8 bits per channel in the PNG, which is what browsers and most viewers use. For analysis that depends on the full precision, use specialist software on the original file.
Greyscale images
Single-channel JPEG 2000 files, common for scanned text and some imagery, are converted to grey PNGs. They are stored as full-colour PNGs with equal red, green and blue values, which every app reads correctly.
JPEG 2000 and PNG compared
| JPEG 2000 | PNG | |
|---|---|---|
| First released | 2000 | 1996 |
| Compression | Lossy or lossless (wavelets) | Lossless |
| Transparency | Yes | Yes, including soft edges |
| Animation or pages | Tiles and resolution levels | Only as APNG, rarely used |
| Best for | Archives, mapping, medical and cinema | Screenshots, graphics, text and transparency |
| Support | Specialist software; little browser support | Universal |
Questions people ask
Is JP2 to PNG lossless?
Yes for 8-bit images. Higher bit depths are scaled to 8 bits per channel.
Why is the PNG larger than the JP2?
JPEG 2000 compresses more efficiently than PNG, both lossy and lossless.
Can I convert J2K codestreams as well as JP2?
Yes, both are supported.