title: Brightness filter in firefox and opera without svg file
body: <p>For my current project i used filter    <code>-webkit-filter: brightness(-20%);-moz-filter: brightness(-20%);</code>     But somewhy, this filter doesnt works in firefox and opera(i have opera prefix too). I found, the way how this can be used, but i need to turn brightness filter into svg code. Any ideas how can i do this?<br>
  What i have to do, is a small gallery, with darkened images, and with normal images on hover without using 2x images.</p>