From 3754a77d87b5e746042883049dc01afc9e1b16b7 Mon Sep 17 00:00:00 2001
From: Chuck Walbourn <walbourn@users.noreply.github.com>
Date: Mon, 11 Sep 2023 23:13:35 -0700
Subject: [PATCH] DDS_FLAGS_PERMISSIVE flag to allow some file variants with
 header bugs (#394)

---
 DirectXTex/DirectXTex.h      |  3 +++
 DirectXTex/DirectXTexDDS.cpp | 31 +++++++++++++++++++++++++++----
 Texconv/texconv.cpp          |  4 ++++
 3 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/DirectXTex/DirectXTex.h b/DirectXTex/DirectXTex.h
index eae8e62..2bc5cc4 100644
--- a/DirectXTex/DirectXTex.h
+++ b/DirectXTex/DirectXTex.h
@@ -226,6 +226,9 @@ namespace DirectX
         DDS_FLAGS_BAD_DXTN_TAILS = 0x40,
         // Some older DXTn DDS files incorrectly handle mipchain tails for blocks smaller than 4x4
 
+        DDS_FLAGS_PERMISSIVE = 0x80,
+        // Allow some file variants due to common bugs in the header written by various leagcy DDS writers
+
         DDS_FLAGS_FORCE_DX10_EXT = 0x10000,
         // Always use the 'DX10' header extension for DDS writer (i.e. don't try to write DX9 compatible DDS files)
 
diff --git a/DirectXTex/DirectXTexDDS.cpp b/DirectXTex/DirectXTexDDS.cpp
index 162308d..32eef41 100644
--- a/DirectXTex/DirectXTexDDS.cpp
+++ b/DirectXTex/DirectXTexDDS.cpp
@@ -346,11 +346,18 @@ namespace
             return E_FAIL;
         }
 
-        if (pHeader->ddspf.size != 0 /* Known variant */
-            && pHeader->ddspf.size != 24 /* Known variant */
-            && pHeader->ddspf.size != sizeof(DDS_PIXELFORMAT))
+        if (flags & DDS_FLAGS_PERMISSIVE)
         {
-            return E_FAIL;
+            if (pHeader->ddspf.size != 0 /* Known variant */
+                && pHeader->ddspf.size != 24 /* Known variant */
+                && pHeader->ddspf.size != sizeof(DDS_PIXELFORMAT))
+            {
+                return HRESULT_E_NOT_SUPPORTED;
+            }
+        }
+        else if (pHeader->ddspf.size != sizeof(DDS_PIXELFORMAT))
+        {
+            return HRESULT_E_NOT_SUPPORTED;
         }
 
         metadata.mipLevels = pHeader->mipMapCount;
@@ -460,6 +467,14 @@ namespace
                 metadata.height = pHeader->height;
                 metadata.depth = pHeader->depth;
                 metadata.dimension = TEX_DIMENSION_TEXTURE3D;
+
+                if (flags & DDS_FLAGS_PERMISSIVE)
+                {
+                    // Allow cases where mipCount was computed incorrectly
+                    size_t maxMips = 0;
+                    std::ignore = Internal::CalculateMipLevels3D(metadata.width, metadata.height, metadata.depth, maxMips);
+                    metadata.mipLevels = std::min(metadata.mipLevels, maxMips);
+                }
             }
             else
             {
@@ -479,6 +494,14 @@ namespace
                 metadata.dimension = TEX_DIMENSION_TEXTURE2D;
 
                 // Note there's no way for a legacy Direct3D 9 DDS to express a '1D' texture
+
+                if (flags & DDS_FLAGS_PERMISSIVE)
+                {
+                    // Allow cases where mipCount was computed incorrectly
+                    size_t maxMips = 0;
+                    std::ignore = Internal::CalculateMipLevels(metadata.width, metadata.height, maxMips);
+                    metadata.mipLevels = std::min(metadata.mipLevels, maxMips);
+                }
             }
 
             metadata.format = GetDXGIFormat(*pHeader, pHeader->ddspf, flags, convFlags);
diff --git a/Texconv/texconv.cpp b/Texconv/texconv.cpp
index f7538b3..53ece5c 100644
--- a/Texconv/texconv.cpp
+++ b/Texconv/texconv.cpp
@@ -94,6 +94,7 @@ namespace
         OPT_VFLIP,
         OPT_DDS_DWORD_ALIGN,
         OPT_DDS_BAD_DXTN_TAILS,
+        OPT_DDS_PERMISSIVE,
         OPT_USE_DX10,
         OPT_USE_DX9,
         OPT_TGA20,
@@ -190,6 +191,7 @@ namespace
         { L"vflip",         OPT_VFLIP },
         { L"dword",         OPT_DDS_DWORD_ALIGN },
         { L"badtails",      OPT_DDS_BAD_DXTN_TAILS },
+        { L"permissive",    OPT_DDS_PERMISSIVE },
         { L"dx10",          OPT_USE_DX10 },
         { L"dx9",           OPT_USE_DX9 },
         { L"tga20",         OPT_TGA20 },
@@ -2104,6 +2106,8 @@ int __cdecl wmain(_In_ int argc, _In_z_count_(argc) wchar_t* argv[])
                 ddsFlags |= DDS_FLAGS_EXPAND_LUMINANCE;
             if (dwOptions & (uint64_t(1) << OPT_DDS_BAD_DXTN_TAILS))
                 ddsFlags |= DDS_FLAGS_BAD_DXTN_TAILS;
+            if (dwOptions & (uint64_t(1) << OPT_DDS_PERMISSIVE))
+                ddsFlags |= DDS_FLAGS_PERMISSIVE;
 
             hr = LoadFromDDSFile(curpath.c_str(), ddsFlags, &info, *image);
             if (FAILED(hr))