Brian Gregory wrote:
On 18/02/2020 23:33, Brian Gregory wrote:
Get a selection of PNG files, some photos and some graphics and you'll
see how much of an improvement optipng can make. Usually not much,
maybe 2% if you're lucky but when a PNG is going on a website why not
do it? If you see more than that it probably means the original PNG
wasn't compressed properly.

Which, can we agree, is fairly unusual?

On a day to day basic, I don't have much reason to
examine the topic. When I download images, I have enough disk space
I don't really care about potential savings. If something is
too big, I'd just throw it away.

It was only the one large graphic, where I was trying to find
some way to make the file manageable. And PNG, with the selection
of palettes it offered, was the solution. I might have used
netpbm or something, to get the degree of control needed.
I don't think I could set GIMP to a four color palette.
I must have used some other method. I'm not sure I could
open it in GIMP (not enough memory on this machine).

I don't think I tried any optimizer on that particular file,
as a brute force run on something that size would likely
never finish. But the palette change, did make it possible
to store the file without it being inconveniently big.

My problem now, is I can't find the file, to refresh my
memory on what it was for. It's gone off to some backup
drive I would guess.

And the only conventional images that large, would be
the ones I made with Microsoft ICE (panorama stitching software).
The .psb format worked for that, and that was good enough.

https://en.wikipedia.org/wiki/Adobe_Photoshop

"Photoshop files sometimes have the file extension .PSB,
which stands for "Photoshop Big" (also known as "large
document format"). A PSB file extends the PSD file format,
increasing the maximum height and width to 300,000 pixels
and the length limit to around 4 Exabytes."

The output quality of ICE wasn't that good, so as tests go it
was kind of a flop. I understand the fill capabilities
of the current Adobe Photoshop are pretty amazing. If a
panorama has holes in it or missing photos in the sequence,
some softwares will offer to fill the holes with a matching
pattern. ICE left a few spots with all-black.

Paul