watermark for the pictures

[rallek]

imagine gives the possibility to create watermarks. It should be added in the \Classifieds\lib\Classifieds\Util\Image.php

see: http://imagine.readthedocs.org/en/latest/usage/introduction.html#image-watermarking

$watermark = $imagine->open('/my/watermark.png');
$image     = $imagine->open('/path/to/image.jpg');
$size      = $image->getSize();
$wSize     = $watermark->getSize();

$bottomRight = new Imagine\Image\Point($size->getX() - $wSize->getX(), $size->getY() - $wSize->getY());

$image->paste($watermark, $bottomRight);

• a picture for a watermark should be uploadable (modVar)
• feature should be optional (disable by boolean)
• a folder should be available (possibly created automatically by MOST model? if not, take care about availability during install?)

[rallek]

needed for #15