TYPO3 Core

[GFX][im] = 0 => Pictures are shown (in original size)

Do you have safe_mode active?

No, it's off.

I tried many configurations, here is one of them, causing troubles (perhaps someone can write it into my first post):

[GFX]
[image_processing]=1
[thumbnails]=1
[thumbnails_png]=0
[noIconProc]=
[gif_compress]=0
[imagefile_ext]=gif,jpg,jpeg,tif,bmp,pcx,tga,png,pdf,ai
[gdlib]=1
[gdlib_png]=0
[gdlib_2]=0
[im]=1
[im_path]=/srv/www/vhosts/[...]/httpdocs/imagemagick-4.2.9/bin/
[im_path_lzw]=
[im_version_5]=
[im_negate_mask]=
[im_imvMaskState]=
[im_no_effects]=0
[im_v5effects]=-1
[im_mask_temp_ext_gif]=0
[im_mask_temp_ext_noloss]=miff
[im_noScaleUp]=
[im_combine_filename]=combine
[im_noFramePrepended]=
[im_stripProfileCommand]=+profile '*' ("+profil" makes no difference)
[im_useStripProfileByDefault]=0
[jpg_quality]=100
[enable_typo3temp_db_tracking]=
[TTFLocaleConv]=
[TTFdpi]=72
[png_truecolor]=

safe_mode = off

Typo3 4.3.3
ImageMagick 4.2.9 (same problem with: ImageMagick 6.6.1 & GraphicsMagick 1.1.6)
PHP 5.2.12 (sorry, I wrote the wrong version above)
tt_news 2.5.2

Do you need more information?

What processes are hanging? Can you post the command, which seems to fail?

The processes are "convert" and "convert.bin". They appear up to 150 times before the server breaks down. systemLog (level 0) doesn't give any hints.

Where can I find the commands which seems to fail?

Please have a look at the imagemagick-whatever function in t3lib/class.t3lib_div.php and output its results.
Then try to enter this on a command line.

That's, what the function imageMagickCommand does:

/srv/www/vhosts/[...]/httpdocs/imagemagick-4.2.9/bin/convert -geometry 27x40! -colorspace RGB -sharpen 50 -quality 100 'uploads/pics/test.jpg⁰'[0] 'typo3temp/pics/caf11c28ce.jpg'

And that's what ImageMagick answers:

convert: no delegate for this image format (JPG⁰).
convert: Missing an image file name [No such file or directory].

The path to the picture without "[0]" exists.

[0] is the first frame/page of an image/document, so this is okay. But I'm a bit curious of the second '[0] after test.jpg⁰.

Do you think you can find out, where this comes from?

I found the cause of the second "[0]". [im_noFramePrepended] has to be enabled.

BUT images still aren't rendered. While using the absolute path, everything is fine, but TYPO3 uses "uploads/pics/test.jpg⁰" instead of "/srv/www/vhosts/domain.com/httpdocs/dummy/uploads/pics/test.jpg⁰". Do you know, where this can be changed?

Now, without the absolute path, ImageMagick says:
convert: Unable to open file (uploads/pics/test.jpg).
convert: Missing an image file name [No such file or directory].

Image scaling also does not work in 4.4.2 and with graphicsmagick, as long as im_noFramePrepended is not set to 1. Apparently newer TYPO3 cores build an illegal command string without im_noFramePrepended.