[Webkit-unassigned] [Bug 20211] New: compress PNG images

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Tue Jul 29 11:42:55 PDT 2008


           Summary: compress PNG images
           Product: WebKit
           Version: 526+ (Nightly build)
          Platform: All
        OS/Version: All
            Status: UNCONFIRMED
          Severity: Enhancement
          Priority: P2
         Component: WebKit Misc.
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: dimitri at trolltech.com

I suggest compressing the PNG images in WebKit using a tool such as "optipng"
and possibly "pngout":

Two reasons for compressing images:
1) Compressed images result in smaller source packages and binaries.
2) Compressed images load faster.

I see two main options for compressing images:
1) Compress using "optipng -nc -o7" which doesn't change color type (for
example "8-bit/color RGB" won't be changed into "8-bit colormap"). It is
probably important for artists not to change the color type...
2) Compress using plain "optipng -o7" and "pngout". This achieves much better
compression, but often changes the color type.

Here is what you can expect from PNG image compression, from the point of view
of source package size:
        $ du -sb WebKit-r35417.orig
        44918896        WebKit-r35417.orig
        $ du -sb WebKit-r35417.optipng-nc
        44908175        WebKit-r35417.optipng-nc
        $ du -sb WebKit-r35417.optipng+pngout
        44625618        WebKit-r35417.optipng+pngout
With "optipng -nc":
        10721 bytes less, 0.02% of the source package
With "optipng" and "pngout":
        293278 bytes less, 0.65% of the source package

I know: that's not much. Chances are speed improvements in loading images might
be marginal as well. Still... What about it?

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