implemented PSM images (#80)

ArcFormats/ArcFormats.csproj

@@ -107,6 +107,7 @@
     <Compile Include="Foster\ImageC24.cs" />
     <Compile Include="GameSystem\ArcPureMail.cs" />
     <Compile Include="GameSystem\AudioADP4.cs" />
+    <Compile Include="ImagePSM.cs" />
     <Compile Include="Kaas\ArcPB.cs" />
     <Compile Include="Kaas\AudioKAAS.cs" />
     <Compile Include="Kaguya\ArcAN21.cs" />

ArcFormats/ImagePSM.cs

@@ -0,0 +1,63 @@
+//! \file       ImagePSM.cs
+//! \date       Fri Jul 07 19:16:57 2017
+//! \brief      Obfuscated PNG image.
+//
+// Copyright (C) 2017 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.ComponentModel.Composition;
+using System.IO;
+
+namespace GameRes.Formats.Misc
+{
+    [Export(typeof(ImageFormat))]
+    public class PsmFormat : PngFormat
+    {
+        public override string         Tag { get { return "PSM"; } }
+        public override string Description { get { return "Obfuscated PNG image"; } }
+        public override uint     Signature { get { return 0x474E50ED; } }
+
+        public override ImageData Read (IBinaryStream file, ImageMetaData info)
+        {
+            using (var png = DeobfuscateStream (file))
+                return base.Read (png, info);
+        }
+
+        IBinaryStream DeobfuscateStream (IBinaryStream file)
+        {
+            var header = file.ReadHeader (4).ToArray();
+            header[0] = 0x89;
+            var body = new StreamRegion (file.AsStream, 4, true);
+            var png = new PrefixStream (header, body);
+            return new BinaryStream (png, file.Name);
+        }
+
+        public override void Write (Stream file, ImageData image)
+        {
+            var start_pos = file.Position;
+            base.Write (file, image);
+            var end_pos = file.Position;
+            file.Position = start_pos;
+            file.WriteByte (0xED);
+            file.Position = end_pos;
+        }
+    }
+}