LiveCD optimisations explained

John Moser john.r.moser at
Fri May 21 19:31:19 UTC 2010

Meh android top-posting.

Png is totally lossless.  It analyzes each scanline versus the prior, and
recodes.  Thus a top to bottom gradient becomes a field of identical
repeating numbers using the SUB filter, which compresses extremely well.
There are several filters; png has many operating modes.

On May 21, 2010 3:06 PM, "Phillip Susi" <psusi at> wrote:

On 5/21/2010 1:40 PM, Louis Simard wrote: > Err... While I know what you
want me to do (you want > C...
Heh, yea, I've struggled with this on thunderbird too, which is why I
usually end up submitting patches via something like mime-construct or
some other command line mime editor where I can force it to use
Content-Disposition: inline.

> - For PNG: the data used to store some images on the CD is not >
compressed to the highest level....
I believe that PNG applies a lossey compression first, then gzips the
result.  It sounds like you are saying that the gzip is done with -3
instead of -9, so you ungzip it and recompress on -9.  Is that more or
less correct?  If so that sounds pretty good, but like you mentioned
before, should be done upstream rather than only for the livecd.

> - For SVG: the data used to store ALL images on the CD is not optimal >
for rendering purposes. I...
Sounds good, and also would be good to do upstream instead of just for
the lived.

> - For XML, as described by Martin Owens: xmllint would remove > everything
superfluous from all f...
I noticed the bloated gconf xml files a few years back myself and
brought it up on the devel list.  IIRC I saw even more wasted space than
you mention here, due to 10, 20, even 30 characters of whitespace
indenting each line.  This does add a lot of bloat to the files I don't
like to have on an installed system, but once compressed into the
squashfs for the livecd, the whitespace drops out, so there wasn't much
concern about it.  At one point I tried just converting the whitespace
into hard tabs and saved quite a bit of space, while preserving the
indentation for human editing.

-- Ubuntu-devel-discuss mailing list
Ubuntu-devel-discuss at lists.ubuntu.comModify settings or unsu...
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <>

More information about the Ubuntu-devel-discuss mailing list