  // picoPNG version 20101224
  // Copyright (c) 2005-2010 Lode Vandevenne
  //
  // 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.
  
  // picoPNG is a PNG decoder in one C++ function of around 500 lines. Use picoPNG for
  // programs that need only 1 .cpp file. Since it's a single function, it's very limited,
  // it can convert a PNG to raw pixel data either converted to 32-bit RGBA color or
  // with no color conversion at all. For anything more complex, another tiny library
  // is available: LodePNG (lodepng.c(pp)), which is a single source and header file.
  // Apologies for the compact code style, it's to make this tiny.