[TYPO3-english] typo3 + imagemagick + scaling of alpha transparent pngs

Jigal van Hemert jigal at xs4all.nl
Fri Aug 20 22:06:18 CEST 2010


On 20-8-2010 17:16, horace grant wrote:
> i am not combining images though. they just get scaled. is this the
> same problem then?

Maybe. It was just to illustrate the fact that the image function are 
simply not written with alpha transparency in mind. Besides the image 
functions must support ImageMagick 4, 5 and 6 plus GraphicsMagick. Both 
tools have strange bugs in all kinds of sub-versions.

It's easy to see if the scaling is done with IM/GM or with PHP GD functions:
The install tool has in the graphics test section also a few image 
scaling tests. Here the exact command line commands are shown to produce 
the test images. If you run those commands with your PNG image and the 
result is different from what you see in the website then it must be 
using GD functions.

> i also tried this on the server of a friend now which uses imagemagick
> (instead of graphicsmagick) and while scaled transparent pngs look a
> lot less broken it doesn't really work there either. there lots of
> "firefly" pixels and the transparency is much less exact (doesn't look
> like gif transparency though - more like the alpha channel has extreme
> jpg artifacts :)).

Can you put the images (original, scaled by your server, scaled by 
friends server) online somewhere, or send them to me?
Please include info on version of OS, PHP, TYPO3, IM/GM and GFX settings 
from install tool. This can help find the cause of problems with images.

Kind regards / met vriendelijke groet,

Jigal van Hemert
msn: jigal at xs4all.nl

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