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//! \file ImageRPGMV.cs
//! \date 2018 Oct 14
//! \brief RPG Maker encrypted PNG image.
//
// Copyright (C) 2018 by morkt
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to
// deal in the Software without restriction, including without limitation the
// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
// sell copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
// IN THE SOFTWARE.
//
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel.Composition;
using System.IO;
using System.Text;
using System.Web.Script.Serialization;
namespace GameRes.Formats.RPGMaker
{
internal class RpgmvpMetaData : ImageMetaData
{
public byte[] Key;
}
[Export(typeof(ImageFormat))]
public class RpgmvpFormat : ImageFormat
{
public override string Tag { get { return "RPGMVP"; } }
public override string Description { get { return "RPG Maker engine image format"; } }
public override uint Signature { get { return 0x4D475052; } } // 'RPGMV'
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public RpgmvpFormat ()
{
Extensions = new string[] { "rpgmvp", "png_" };
}
public override ImageMetaData ReadMetaData (IBinaryStream file)
{
var header = file.ReadHeader (0x14);
if (header[4] != 'V')
return null;
var key = RpgmvDecryptor.LastKey ?? RpgmvDecryptor.FindKeyFor (file.Name);
if (null == key)
return null;
for (int i = 0; i < 4; ++i)
header[0x10+i] ^= key[i];
if (!header.AsciiEqual (0x10, "\x89PNG"))
{
RpgmvDecryptor.LastKey = null;
return null;
}
RpgmvDecryptor.LastKey = key;
using (var png = RpgmvDecryptor.DecryptStream (file, key, true))
{
var info = Png.ReadMetaData (png);
if (null == info)
return null;
return new RpgmvpMetaData {
Width = info.Width,
Height = info.Height,
OffsetX = info.OffsetX,
OffsetY = info.OffsetY,
BPP = info.BPP,
Key = key,
};
}
}
public override ImageData Read (IBinaryStream file, ImageMetaData info)
{
var meta = (RpgmvpMetaData)info;
using (var png = RpgmvDecryptor.DecryptStream (file, meta.Key, true))
return Png.Read (png, info);
}
public override void Write (Stream file, ImageData image)
{
throw new System.NotImplementedException ("RpgmvpFormat.Write not implemented");
}
}
internal class RpgmvDecryptor
{
public static IBinaryStream DecryptStream (IBinaryStream input, byte[] key, bool leave_open = false)
{
input.Position = 0x10;
var header = input.ReadBytes (key.Length);
for (int i = 0; i < key.Length; ++i)
header[i] ^= key[i];
var result = new PrefixStream (header, new StreamRegion (input.AsStream, input.Position, leave_open));
return new BinaryStream (result, input.Name);
}
static byte[] GetKeyFromString (string hex)
{
if ((hex.Length & 1) != 0)
throw new System.ArgumentException ("invalid key string");
var key = new byte[hex.Length/2];
for (int i = 0; i < key.Length; ++i)
{
key[i] = (byte)(HexToInt (hex[i * 2]) << 4 | HexToInt (hex[i * 2 + 1]));
}
return key;
}
static int HexToInt (char x)
{
if (char.IsDigit (x))
return x - '0';
else
return char.ToUpper (x) - 'A' + 10;
}
static byte[] ParseSystemJson (string filename)
{
var json = File.ReadAllText (filename, Encoding.UTF8);
var serializer = new JavaScriptSerializer();
var sys = serializer.DeserializeObject (json) as IDictionary;
if (null == sys)
return null;
var key = sys["encryptionKey"] as string;
if (null == key)
return null;
return GetKeyFromString (key);
}
public static byte[] FindKeyFor (string filename)
{
foreach (var system_filename in FindSystemJson (filename))
{
if (File.Exists (system_filename))
return ParseSystemJson (system_filename);
}
return null;
}
static IEnumerable<string> FindSystemJson (string filename)
{
var dir_name = Path.GetDirectoryName (filename);
yield return Path.Combine (dir_name, @"..\..\data\System.json");
yield return Path.Combine (dir_name, @"..\..\..\www\data\System.json");
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yield return Path.Combine (dir_name, @"..\..\..\data\System.json");
yield return Path.Combine (dir_name, @"..\..\..\..\data\System.json");
yield return Path.Combine (dir_name, @"..\data\System.json");
yield return Path.Combine (dir_name, @"data\System.json");
}
internal static readonly byte[] DefaultKey = {
0x77, 0x4E, 0x46, 0x45, 0xFC, 0x43, 0x2F, 0x71, 0x47, 0x95, 0xA2, 0x43, 0xE5, 0x10, 0x13, 0xD8
};
internal static byte[] LastKey = null;
}
}