[TYPO3] TS: BgrndColor of partially transparent GIFs whenscalingwith IMG_RESOURCE

Joerg Wagner - DigiLog multimedia usenet at digilog.de
Tue Mar 14 09:36:08 CET 2006

Hi Paul,

thanks for your answer, but you missed the point.
I am aware that GIF only offers 1bit transparency. With "partially 
transparent GIF" I meant that parts of the GIF are transparent, others are 
not, and the problem arises at the edge between those areas when the GIFs 
are scaled down and the IMG_RESOURCE scaling mechanism introduces 
antialiasing at the edge. The antialiasing itself is not the problem, but I 
need to control the color to be AAed against.

Jörg Wagner
DigiLog multimedia

"P H Vetch" <paul at qedstudio.com> schrieb im Newsbeitrag 
news:mailman.11739.1142323551.3122.typo3-english at lists.netfielders.de...
> Hi there,
> The problem you're having has to do with a limitation of the GIF format -
> you can't have partial transparency (only 1 bit alpha supported, so a 
> pixel
> is either 100% transparent or 100% opaque).  The only format which will 
> help
> you is 24bit PNG, though this has it's own drawbacks (namely than the
> transparency isn't supported by IE without some additional work).
> For a handy illstrated explanation of the issue see the bottom of this 
> page:
> http://www.pixy.cz/blogg/clanky/rubberheaders/
> There are plugins in TYPO3 which address the PNG support in IE, have a
> search around.
> Best
> Paul
>> -----Original Message-----
>> From: typo3-english-bounces at lists.netfielders.de
>> [mailto:typo3-english-bounces at lists.netfielders.de] On Behalf
>> Of Joerg Wagner - DigiLog multimedia
>> Sent: 14 March 2006 07:50
>> To: typo3-english at lists.netfielders.de
>> Subject: [TYPO3] TS: BgrndColor of partially transparent GIFs
>> when scalingwith IMG_RESOURCE
>> Hi all !
>> I am trying to use partially transparent GIFs as backgrounds
>> for <div> tags.
>> Where the GIFs are transparent the CSS background-color of
>> the div can be seen as expected. I use hard edges between GIF
>> foreground and transparent background (no antialiasing) so
>> this works fine.
>> The user can select the GIFs in a TemplaVoila FCE and I also
>> have provide for the possibility to scale the GIFs as needed.
>> Now, when I scale the IMG_RESOURCE that renders the GIF as
>> needed (by setting the width or height prop of the
>> IMG_RESOURCE), the edges to the transparent background get
>> antialiased against white color(!) which is not the
>> background-color of my divs, so the edges produce a visible
>> jaggy white glow.
>> Is there any way to define the background color that the
>> IMG_RESOURCE object uses to antialias against when scaling
>> transparent GIFs? TSref shows now such property for IMG_RESOURCE.
>> Thanks for your help.
>> --
>> Jvrg Wagner
>> DigiLog multimedia

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