[TYPO3-core] RFC #16707 : bug : Read from and write to same file hangs GM on network file system

[Jigal van Hemert]

Hi,

This is a SVN patch request.

Type: Bugfix

BT reference: http://bugs.typo3.org/view.php?id=16707

Branches: trunk / 4.4 / 4.3

Problem:
t3lib_div::gif_compress() uses ImageMagick / GraphicsMagick to compress 
GIF files. In this command it uses the same file as input and output. On 
some network file systems this causes the GM to hang.

Solution:
Rename the original GIF to a random name and use this as input for 
IM/GM; remove this file afterwards.

How to test:
Problem is hard to reproduce. Bug tracker mentions system specifications 
where it occurs. All the hanging processes showed a convert command with 
only a profile parameter and same input and output file; this is typical 
for the gif_compress function.

It's easy to see in Install Tool that gif_compress still works fine 
after the patch:
- $TYPO3_CONF_VARS['GFX']['gif_compress'] is set
- $TYPO3_CONF_VARS['GFX']['im'] is set
- $TYPO3_CONF_VARS['GFX']['im_path_lzw'] is set to location of IM/GM
In the Image Processing section, Writing GIF and PNG should show below 
the Write GIF test a message like:

Note on gif_compress() function:
The 'gif_compress' method used was 'IM'.
Previous filesize: 21 K. Current filesize:21 K

-- 
Jigal van Hemert
skype:jigal.van.hemert
msn: jigal at xs4all.nl
http://twitter.com/jigalvh

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