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

[horace grant]

On Fri, Aug 20, 2010 at 10:06 PM, Jigal van Hemert <jigal at xs4all.nl> wrote:
> Hi,
>
> 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.



when i was collecting all the information and example files for you, i
came across the [png_truecolor] config option. i set to to 1 and now
scaling works perfectly on both systems (imagemagick +
graphicsmagick). i didn't think of this since on the graphicsmagick
system it didn't look like a truecolor<->palette problem but much more
severe since the image also was distorted.

thanks for getting me to look in the right spots... :)

cheers,
horace



>
> --
> Kind regards / met vriendelijke groet,
>
> Jigal van Hemert
> skype:jigal.van.hemert
> msn: jigal at xs4all.nl
> http://twitter.com/jigalvh
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