From 75d7d3307d2d7525b3212acf643f3d6627cb8edb Mon Sep 17 00:00:00 2001
From: morkt <morkt@users.noreply.github.com>
Date: Fri, 31 Aug 2018 04:32:13 +0400
Subject: [PATCH] (BgiFormat): restore scrambled pixels.

---
 ArcFormats/Ethornell/ImageBGI.cs | 63 ++++++++++++++++++++++++++++----
 1 file changed, 55 insertions(+), 8 deletions(-)

diff --git a/ArcFormats/Ethornell/ImageBGI.cs b/ArcFormats/Ethornell/ImageBGI.cs
index 99edac15..b2630569 100644
--- a/ArcFormats/Ethornell/ImageBGI.cs
+++ b/ArcFormats/Ethornell/ImageBGI.cs
@@ -34,6 +34,11 @@ using System.Threading.Tasks;
 
 namespace GameRes.Formats.BGI
 {
+    internal class BgiMetaData : ImageMetaData
+    {
+        public bool IsScrambled;
+    }
+
     [Export(typeof(ImageFormat))]
     public class BgiFormat : ImageFormat
     {
@@ -43,7 +48,7 @@ namespace GameRes.Formats.BGI
 
         public BgiFormat ()
         {
-            Extensions = new string[] { "", "bgi" };
+            Extensions = new string[] { "", "bgi", "_bg" };
         }
 
         public override void Write (Stream file, ImageData image)
@@ -57,21 +62,26 @@ namespace GameRes.Formats.BGI
             int height = stream.ReadInt16();
             if (width <= 0 || height <= 0)
                 return null;
-            int bpp = stream.ReadInt32();
+            int bpp = stream.ReadInt16();
             if (24 != bpp && 32 != bpp && 8 != bpp)
                 return null;
+            int flag = stream.ReadInt16();
+            if (flag != 1 && flag != 0)
+                return null;
             if (0 != stream.ReadInt64())
                 return null;
-            return new ImageMetaData
+            return new BgiMetaData
             {
                 Width = (uint)width,
                 Height = (uint)height,
                 BPP = bpp,
+                IsScrambled = flag != 0,
             };
         }
 
         public override ImageData Read (IBinaryStream stream, ImageMetaData info)
         {
+            var meta = (BgiMetaData)info;
             PixelFormat format;
             if (24 == info.BPP)
                 format = PixelFormats.Bgr24;
@@ -79,14 +89,51 @@ namespace GameRes.Formats.BGI
                 format = PixelFormats.Bgra32;
             else
                 format = PixelFormats.Gray8;
-            int stride = (int)info.Width*((info.BPP+7)/8);
-            var pixels = new byte[stride*info.Height];
+            int stride = (int)info.Width * ((info.BPP+7)/8);
+            var pixels = new byte[stride * (int)info.Height];
             stream.Position = 0x10;
-            int read = stream.Read (pixels, 0, pixels.Length);
-            if (read != pixels.Length)
-                throw new InvalidFormatException();
+            if (!meta.IsScrambled)
+            {
+                int read = stream.Read (pixels, 0, pixels.Length);
+                if (read != pixels.Length)
+                    throw new InvalidFormatException();
+            }
+            else
+            {
+                RestorePixels (stream, pixels, meta);
+            }
             return ImageData.Create (info, format, null, pixels, stride);
         }
+
+        void RestorePixels (IBinaryStream input, byte[] output, BgiMetaData info)
+        {
+            int bpp = info.BPP / 8;
+            int stride = (int)info.Width * bpp;
+            for (int i = 0; i < bpp; ++i)
+            {
+                int dst = i;
+                byte incr = 0;
+                for (int h = (int)info.Height; h > 0; --h)
+                {
+                    for (uint w = 0; w < info.Width; ++w)
+                    {
+                        incr += input.ReadUInt8();
+                        output[dst] = incr;
+                        dst += bpp;
+                    }
+                    if (--h == 0)
+                        break;
+                    dst += stride;
+                    int pos = dst;
+                    for (uint w = 0; w < info.Width; ++w)
+                    {
+                        pos -= bpp;
+                        incr += input.ReadUInt8();
+                        output[pos] = incr;
+                    }
+                }
+            }
+        }
     }
 
     internal class CbgMetaData : ImageMetaData