What lossy formats can compress 16-bit grayscale images without reducing dynamic range?
Asked 7/17/2015
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I need to aggressively compress scientific 16-bit grayscale image files while keeping their high dynamic range. JPEG gives adjustable lossy compression, but it is typically limited to 8-bit channels. PNG supports 16-bit grayscale, but only with lossless compression, so file size savings are limited. TIFF can store 16-bit data, but I’m not aware of a standard lossy option for this use. Is there a lossy format that supports 16-bit grayscale images, or another practical way to preserve dynamic range while reducing file size?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
11y ago
2 Answers
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It sounds like what you're looking for is JPEG2000. It has a range of options including a 16-bit lossy compression and better compression ratios than JPEG. It hasn't been as widely adopted as hoped (for a host of reasons) and may have some patent issues that might make it difficult to use in certain situations but otherwise it fits your needs.
Personally if I were in your position I'd say storage is cheap and use PNG which is a properly defined and free standard.
Originally by user14028. Source · Licensed CC BY-SA 4.0
user14028
11y ago
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Yes. The format most directly matching your requirements is JPEG 2000, which supports 16-bit imagery and lossy compression. It was specifically suggested as fitting this use case better than standard JPEG, though it is less widely adopted.
Another format worth looking at is OpenEXR, which was also suggested, especially where video/imaging pipelines support it.
A different approach is to remap the data before compression: apply a strong nonlinear tone curve, store the result as an 8-bit JPEG, then later expand it back with the inverse curve. This can preserve dynamic range better than linear 8-bit encoding, but it does not necessarily preserve tonal precision the same way as true 16-bit storage.
If you need a standard, purpose-built lossy format for 16-bit grayscale data, JPEG 2000 is the clearest answer from the options discussed. If maximum fidelity matters more than compression ratio, lossless 16-bit formats such as PNG may still be the safer choice.
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