zlib/libpng license 
 This software is provided 'as-is', without any express or implied warranty. In 
 no event will the authors be held liable for any damages arising from the use
 of this software. 
 Permission is granted to anyone to use this software for any purpose, including 
 commercial applications, and to alter it and redistribute it freely, subject to 
 the following restrictions: 
   1. The origin of this software must not be misrepresented; you must not
      claim that you wrote the original software. If you use this software in
      a product, an acknowledgment in the product documentation would be
      appreciated but is not required. 
   2. Altered source versions must be plainly marked as such, and must not be
      misrepresented as being the original software. 
   3. This notice may not be removed or altered from any source distribution.