[Clipart] [Bug 3347] PNG files not optimized

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Fri May 20 23:51:08 PDT 2005

Please do not reply to this email: if you want to comment on the bug, go to    
the URL shown below and enter yourcomments there.     

karl at huftis.org changed:

           What    |Removed                     |Added
                 CC|                            |karl at huftis.org

------- Additional Comments From karl at huftis.org  2005-05-20 23:51 -------
The best program to use, is OptiPNG. And it's actually better (more
user-friendly) to make the files slightly larger, by using Adam7 interlacing.

Adam7 is a technique where the user can see a (low-resolution) version of the
(entire, undistorted) image as soon as 1/64 is downloaded. This is gradually
improved as 1/32, 1/16, 1/8, 1/4, 1/2 and the rest of the image is downloaded --
all in all 7 passes.

This is much more user-friendly for low-bandwidth users than making the images
even smaller by not using Adam7. (The downloadable archives should use
OptiPNG-optimised images without Adam7 interlacing.) Adam7 is well-supported by
browsers (though IE uses a rather stupid rendering algorithm).

Here are some images domonstrating and explaining Adam7:


And here's my own page, showing all 7 Adam7 passes on a couple of the
OpenClipart.org images (the smiley and the four-leaf clover). The actual page is
in Norwegian, but the images should speak for themselves.

This is the command which should be run on the files to get interlacing and
(almost) optimal compression:

optipng -o7 -i1 filename.png          
Configure bugmail: https://bugs.freedesktop.org/userprefs.cgi?tab=email         
------- You are receiving this mail because: -------
You are the assignee for the bug, or are watching the assignee.

More information about the clipart mailing list