[webkit-dev] optimising png files in LayoutTests - an experiment

[Adam Barth]

On Tue, Jan 24, 2012 at 10:43 PM, Mike Lawther <mikelawther at chromium.org> wrote:
> Just thought I'd share the results of an experiment I did in optimising the
> png files in LayoutTests.
>
> I used a tool on Mac called ImageOptim (http://imageoptim.pornel.net/) which
> tries a set of different png lossless optimising tools (like pngcrush - I
> also downloaded and included PNGOUT). Note that this strips out some of the
> stuff we need, like the hash, so if doing this for real we'd have to watch
> out for that.
>
> My results were:
>
> Before:
> $ ls -laR LayoutTests/ | grep png$ | awk '{total = total + $5}END{print
> total}'
> 1220535840
>
> Test:
> $ find LayoutTests/ | grep png$ | xargs open -a ImageOptim.app
>
> After:
> $ ls -laR LayoutTests/ | grep png$ | awk '{total = total + $5}END{print
> total, 1220535840 - total}'
> 937198328 283337512
>
> So this has saved ~280MB (~23% of the original size).
>
> Based on this, it seems worthwhile to include a png optimiser somewhere in
> the patch upload/submit toolchain, and also (separately) to optimise the
> existing pngs.
>
> Thoughts?

Seems worth including in run-webkit-tests so that we generate
optimized PNGs.  That will cause us to slowly optimize our PNGs.
Note: we do use some of the metadata in the PNGs (e.g., the image hash
is stored in PNG metadata), which means we can't strip it call out.

Adam