The included 'libspng' code is Copyright (c) 2018-2023, Randy <randy408@protonmail.com>.
See 'LICENSE-libspng.txt' for the LICENSE file from the original 'libspng' source code.


The 'spng' source also contains code copyright by other authors:


/* The following SIMD optimizations are derived from libpng source code. */

/*
* PNG Reference Library License version 2
*
* Copyright (c) 1995-2019 The PNG Reference Library Authors.
* Copyright (c) 2018-2019 Cosmin Truta.
* Copyright (c) 2000-2002, 2004, 2006-2018 Glenn Randers-Pehrson.
* Copyright (c) 1996-1997 Andreas Dilger.
* Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
*
* The software is supplied "as is", without warranty of any kind,
* express or implied, including, without limitation, the warranties
* of merchantability, fitness for a particular purpose, title, and
* non-infringement.  In no event shall the Copyright owners, or
* anyone distributing the software, be liable for any damages or
* other liability, whether in contract, tort or otherwise, arising
* from, out of, or in connection with the software, or the use or
* other dealings in the software, even if advised of the possibility
* of such damage.
*
* Permission is hereby granted to use, copy, modify, and distribute
* this software, or portions hereof, for any purpose, without fee,
* 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 Copyright notice may not be removed or altered from any
*     source or altered source distribution.
*/


/* SSE2 optimised filter functions
 * Derived from filter_neon_intrinsics.c
 *
 * Copyright (c) 2018 Cosmin Truta
 * Copyright (c) 2016-2017 Glenn Randers-Pehrson
 * Written by Mike Klein and Matt Sarett
 * Derived from arm/filter_neon_intrinsics.c
 *
 * This code is derived from libpng source code.
 * For conditions of distribution and use, see the disclaimer
 * and license above.
 */
 
 
 /* NEON optimised filter functions
 * Derived from filter_neon_intrinsics.c
 *
 * Copyright (c) 2018 Cosmin Truta
 * Copyright (c) 2014,2016 Glenn Randers-Pehrson
 * Written by James Yu <james.yu at linaro.org>, October 2013.
 * Based on filter_neon.S, written by Mans Rullgard, 2011.
 *
 * This code is derived from libpng source code.
 * For conditions of distribution and use, see the disclaimer
 * and license in this file.
 */
 
 
 /* NEON optimised palette expansion functions
 * Derived from palette_neon_intrinsics.c
 *
 * Copyright (c) 2018-2019 Cosmin Truta
 * Copyright (c) 2017-2018 Arm Holdings. All rights reserved.
 * Written by Richard Townsend <Richard.Townsend@arm.com>, February 2017.
 *
 * This code is derived from libpng source code.
 * For conditions of distribution and use, see the disclaimer
 * and license in this file.
 *
 * Related: https://developer.arm.com/documentation/101964/latest/Color-palette-expansion
 *
 * The functions were refactored to iterate forward.
 *
 */