David Shaw
Mon Sep 22 22:54:05 2003

On Sun, Sep 21, 2003 at 06:40:00PM +0200, Mads Laursen wrote:
> On 20/09/03 20.05, Alan Batie wrote:
> > I went ahead and told it to do the picture thing, and it recommends a
> > 240x288 picture size.  So I tell it to load the 100x127 head shot I saved
> > with photoshop's picture quality 3 (fairly low, out of 10) that is 9k
> > and it complained how huge that was and was I sure I wanted to do that.
> > What is a typical file size for photo id's?  I'd think you'd want them to
> > be a decent resolution or they won't be much good for ID purposes...
> Speaking for myself, I think the picture on my key is quite usable for
> ID purposes (although there is some blocking), and it packs the full
> 240x288 pixels of truecolor jpeg into 2385 bytes. The main trick to
> getting the picture this small was replacing the background with a
> single color. From that point on I just cranked the compression up
> untill I had a small enough file.
> Looking at my keyring (contains mainly keys of people who post to the
> various mailinglists I read), I see keys from 2KB to almost 14KB
> (which I think is a bit over the top), with 3-5KB being the "normal"
> size. 

FWIW, the picture size warning comes up if the picture is over 6KB.
There is nothing magical about that number - when I wrote the code, I
looked at a good number of jpegs from PGP keys, noticed the same thing
that Mads Laursen noticed, and just bumped it up to 6KB to be safe.