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

[horace grant]

On Fri, Aug 20, 2010 at 4:33 PM, David Bruchmann
<typo3-en at bruchmann-web.de> wrote:
> ----- Ursprüngliche Nachricht -----
> Von:        horace grant <horace3d at gmail.com>
> Gesendet:   Freitag, 20. August 2010 16:23:56
> An:         TYPO3 English <typo3-english at lists.typo3.org>
> CC:
> Betreff:    [TYPO3-english] typo3 + imagemagick + scaling of alpha
> transparent  pngs
>>
>> hi,
>>
>> i have a site which requires to use a lot of alpha transparent pngs.
>> the problem is, they look totally broken if they get scaled by
>> typo3/imagemagick.
>>
>> scaling 0/1 gif transparency works ok.
>>
>> is this a general limitation or is something wrong in the imagemagick
>> configuration of my webhoster? or in my typo3 configuration?
>>
>> would be great to know that it isn't my fault. :)
>>
>
>
> Hi Horace,
>
> without examples of original and scaled images and your TypoScript its
> really hard to say - perhaps you can provide some links...



i don't use any special typoscript for scaling images. i mean the
standard content element image scaling behaviour of typo3.

i noticed that my hoster seems to use graphicsmagick:



Current configuration

GraphicsMagick enabled:
    1
GraphicsMagick path:
    /usr/bin/ (1.1.11)
GraphicsMagick path/LZW:
    /usr/bin/ (6.3.7)
Version 5/GraphicsMagick flag:
    gm

GDLib enabled:
    1
GDLib using PNG:

IM5 effects enabled:
    -1 (Blurring/Sharpening with IM 5+)
Freetype DPI:
    96 (Should be 96 for Freetype 2)
Mask invert:
    0 (Should be set for some IM versions approx. 5.4+)

File Formats:
    gif,jpg,jpeg,tif,tiff,bmp,pcx,tga,png,pdf,ai



could this be the reason? all the other image manipulation features
work great though.

i can't post an example of the images since my client probably
wouldn't like that. but they look kind of distorted (like the rows and
columns of pixels get messed up because the alpha byte gets
interpreted wrongly) and the resulting transparency is 0/1
transparency instead of alpha transparency.

cheers, horace



>
> BTW: I scaled pngs in a very good quality and the had transparency too.
>
> Greets,
> David
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