On my PHP 5.5 environment this failed due to "Call to undefined function League\ColorExtractor\imagecreatefrompng()" - the GD functions which are in the global namespace were not properly referenced. Not sure how this ever managed to work in the first place?
Never mind - my bad. It will work, due to fallback to global function names - not sure if we want to rely on that, though. Issue was that GD shipped with PHP5.5 on OSX Yosemite does not include PNG support.
On my PHP 5.5 environment this failed due to "Call to undefined function League\ColorExtractor\imagecreatefrompng()" - the GD functions which are in the global namespace were not properly referenced. Not sure how this ever managed to work in the first place?