You can apply a filter on a layer and its sublayers.
$filterType = IMG_FILTER_SELECTIVE_BLUR; $arg1 = $arg2 = $arg3 = $arg4 = null; $recursive = false; // apply the filter on sublayers $layer->applyFilter($filterType, $arg1, $arg2, $arg3, $arg4, $recursive);
Warning: rather than using the recursive attribute, merge your layers if possible before applying a filter because it could be a possible source of display bugs.
Lets see it in action, we will apply a simple negative filter on the layer:
$layer->applyFilter(IMG_FILTER_NEGATE); // With this filter, we can ignore other params...
Our filter in image: