diff --git a/ArcFormats/ArcFormats.csproj b/ArcFormats/ArcFormats.csproj
index ede066a5..f39cfe37 100644
--- a/ArcFormats/ArcFormats.csproj
+++ b/ArcFormats/ArcFormats.csproj
@@ -224,6 +224,7 @@
     <Compile Include="Seraphim\ArcSCN.cs" />
     <Compile Include="Seraphim\ArcVoice.cs" />
     <Compile Include="ShiinaRio\ArcWARC1.0.cs" />
+    <Compile Include="ShiinaRio\ImageCHD.cs" />
     <Compile Include="Silky\ImageGRD.cs" />
     <Compile Include="Slg\ArcSPD.cs" />
     <Compile Include="Software House Parsley\ArcCG.cs" />
diff --git a/ArcFormats/ShiinaRio/ImageCHD.cs b/ArcFormats/ShiinaRio/ImageCHD.cs
new file mode 100644
index 00000000..497268c3
--- /dev/null
+++ b/ArcFormats/ShiinaRio/ImageCHD.cs
@@ -0,0 +1,130 @@
+//! \file       ImageCHD.cs
+//! \date       2017 Dec 09
+//! \brief      Forest image format.
+//
+// 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;
+using System.Windows.Media;
+
+namespace GameRes.Formats.Forest
+{
+    internal class ChdMetaData : ImageMetaData
+    {
+        public uint FirstOffset;
+    }
+
+    /// <summary>
+    /// ShiinaRio images predecessor.
+    /// </summary>
+    [Export(typeof(ImageFormat))]
+    public class ChdFormat : ImageFormat
+    {
+        public override string         Tag { get { return "CHD"; } }
+        public override string Description { get { return "Forest image format"; } }
+        public override uint     Signature { get { return 0x444843; } } // 'CHD'
+
+        public override ImageMetaData ReadMetaData (IBinaryStream file)
+        {
+            file.Position = 4;
+            int count = file.ReadInt32();
+            if (count < 0 || count > 0xFFFFF)
+                return null;
+            file.ReadInt32();
+            uint first_offset = 0;
+            for (int i = 0; i < count && 0 == first_offset; ++i)
+                first_offset = file.ReadUInt32();
+            if (0 == first_offset)
+                return null;
+            file.Position = first_offset;
+            var info = new ChdMetaData();
+            info.Width = file.ReadUInt32();
+            info.Height = file.ReadUInt32();
+            info.OffsetX = file.ReadInt32();
+            info.OffsetY = file.ReadInt32();
+            info.FirstOffset = first_offset+0x10;
+            info.BPP = 32;
+            return info;
+        }
+
+        public override ImageData Read (IBinaryStream file, ImageMetaData info)
+        {
+            var reader = new ChdReader (file, (ChdMetaData)info);
+            var pixels = reader.Unpack();
+            return ImageData.Create (info, PixelFormats.Gray8, null, pixels);
+        }
+
+        public override void Write (Stream file, ImageData image)
+        {
+            throw new System.NotImplementedException ("ChdFormat.Write not implemented");
+        }
+    }
+
+    internal class ChdReader
+    {
+        IBinaryStream   m_input;
+        int             m_width;
+        int             m_height;
+        uint            m_origin;
+
+        public ChdReader (IBinaryStream input, ChdMetaData info)
+        {
+            m_input = input;
+            m_width = (int)info.Width;
+            m_height = (int)info.Height;
+            m_origin = info.FirstOffset;
+        }
+
+        public byte[] Unpack ()
+        {
+            m_input.Position = m_origin;
+            var rows = new uint[m_height];
+            for (int i = 0; i < m_height; ++i)
+                rows[i] = m_input.ReadUInt32();
+            var output = new byte[m_height*m_width];
+            for (int y = 0; y < m_height; ++y)
+            {
+                m_input.Position = rows[y];
+                int dst = y * m_width;
+                for (int w = m_width; w > 0; )
+                {
+                    int count = m_input.ReadUInt8();
+                    if (0xFF == count)
+                        count = m_input.ReadUInt16();
+                    int x = w - count;
+                    if (0 == x)
+                        break;
+                    count = m_input.ReadUInt8();
+                    if (0 == count)
+                        count = m_input.ReadUInt16();
+                    m_input.Read (output, dst, count);
+                    for (int i = 0; i < count; ++i)
+                        output[dst+i] += 0x57;
+                    dst += count;
+                    w = x - count;
+                }
+            }
+            return output;
+        }
+    }
+}