lossless compression of still images - recommendations?

[David Fletcher]

On Sun, 2017-02-19 at 13:26 -0500, Robert Heller wrote:
> If the OP wants truely lossless compression, he is not going to be
> using JPEG. 
> JPEG is *lossy* compression.  He should be using PNG instead.

I've been watching this thread for a couple of days.

Something that I've seen said before in another thread is that you
can't compress something that's already compressed. My understanding of
PNG is that it operates in much the same way as ZIP i.e. it compresses
images as much as it can but without discarding any information. Any
potentially recurring patterns in the original images will therefore
most probably be concealed withing PNG's compression.

My suggestion would be to store the original images in as raw a format
as possible. How about trying it with good old BMP?

Dave