Re: [libpng:feature-requests] #32 Modern compressor

On 30 December 2016 at 16:41, John Bowler
<[email protected]> wrote:
> It's also debatable whether anything does significantly better than LZW.

For photorealistic images, where PNG performs poorly, the JPEG-LS
standard for lossless and near-lossless compression (based on LOCO-I)
is stronger and way faster than PNG. Given that JPEG-LS was published
as an International Standard back in 1998, the patents covering the
underlying methods required to implement the baseline *may* have
expired by now (but one would have to check).

> One obvious improvement is better encoding of higher dynamic range data; at
> present really expensive digital cameras just exceed the range of 24-bit RGB
> (Sony A7S; the 12MP version which has lower noise) and the output devices in
> development exceed 24-bit RGB by a long way.

I would be happy enough to see our present-day PNG format being used
in digital photography. Never mind exceeding 24-bit. Even for plain
true-color images, deflate-compressed TIFF is more suitable than PNG,
because TIFF can hold EXIF and PNG can't. For digital photographers
(myself included), EXIF is super-precious.

In theory, PNG can hold any metadata. In practice, there have been two
or three attempts by our group to incorporate EXIF into PNG, back in
early 2000's, all of which failed.

PNG can do XMP, instead of EXIF, and yet EXIF is the accepted industry
standard (although Adobe may beg to differ). XMP did not catch on with
any of the digital camera manufacturers that I know.

My favorite digital photography software (DxO Optics Pro) doesn't even
do PNG, and, admittedly, neither do I, for the above-mentioned
reasons.

Sincerely,
Cosmin

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