From 7b4b9b18f7d11004e2bf26da9b083bd577438fff Mon Sep 17 00:00:00 2001
From: Chuck Walbourn <walbourn@users.noreply.github.com>
Date: Tue, 30 Mar 2021 15:16:12 -0700
Subject: [PATCH] NVTT 1.x wrote A8L8 as RGB instead of LUMINANCE (#229)

---
 DDSTextureLoader/DDSTextureLoader11.cpp | 5 +++++
 DDSTextureLoader/DDSTextureLoader12.cpp | 5 +++++
 DDSTextureLoader/DDSTextureLoader9.cpp  | 8 ++++++++
 DirectXTex/DDS.h                        | 3 +++
 DirectXTex/DirectXTexDDS.cpp            | 1 +
 5 files changed, 22 insertions(+)

diff --git a/DDSTextureLoader/DDSTextureLoader11.cpp b/DDSTextureLoader/DDSTextureLoader11.cpp
index d182494..b4f3864 100644
--- a/DDSTextureLoader/DDSTextureLoader11.cpp
+++ b/DDSTextureLoader/DDSTextureLoader11.cpp
@@ -701,6 +701,11 @@ namespace
                     return DXGI_FORMAT_B4G4R4A4_UNORM;
                 }
 
+                if (ISBITMASK(0x00ff, 0, 0, 0xff00))
+                {
+                    return DXGI_FORMAT_R8G8_UNORM; // NVTT versions 1.x wrote this as RGB instead of LUMINANCE
+                }
+
                 // No DXGI format maps to ISBITMASK(0x0f00,0x00f0,0x000f,0) aka D3DFMT_X4R4G4B4
 
                 // No 3:3:2, 3:3:2:8, or paletted DXGI formats aka D3DFMT_A8R3G3B2, D3DFMT_R3G3B2, D3DFMT_P8, D3DFMT_A8P8, etc.
diff --git a/DDSTextureLoader/DDSTextureLoader12.cpp b/DDSTextureLoader/DDSTextureLoader12.cpp
index 58edc63..4489eb6 100644
--- a/DDSTextureLoader/DDSTextureLoader12.cpp
+++ b/DDSTextureLoader/DDSTextureLoader12.cpp
@@ -781,6 +781,11 @@ namespace
                     return DXGI_FORMAT_B4G4R4A4_UNORM;
                 }
 
+                if (ISBITMASK(0x00ff, 0, 0, 0xff00))
+                {
+                    return DXGI_FORMAT_R8G8_UNORM; // NVTT versions 1.x wrote this as RGB instead of LUMINANCE
+                }
+
                 // No DXGI format maps to ISBITMASK(0x0f00,0x00f0,0x000f,0) aka D3DFMT_X4R4G4B4
 
                 // No 3:3:2, 3:3:2:8, or paletted DXGI formats aka D3DFMT_A8R3G3B2, D3DFMT_R3G3B2, D3DFMT_P8, D3DFMT_A8P8, etc.
diff --git a/DDSTextureLoader/DDSTextureLoader9.cpp b/DDSTextureLoader/DDSTextureLoader9.cpp
index 19aa12d..2c1e0da 100644
--- a/DDSTextureLoader/DDSTextureLoader9.cpp
+++ b/DDSTextureLoader/DDSTextureLoader9.cpp
@@ -585,6 +585,10 @@ namespace
                 {
                     return D3DFMT_A8R3G3B2;
                 }
+                if (ISBITMASK(0x00ff, 0, 0, 0xff00))
+                {
+                    return D3DFMT_A8L8; // NVTT versions 1.x wrote this as RGB instead of LUMINANCE
+                }
                 break;
 
             case 8:
@@ -609,6 +613,10 @@ namespace
                 {
                     return D3DFMT_L8;
                 }
+                if (ISBITMASK(0x00ff, 0, 0, 0xff00))
+                {
+                    return D3DFMT_A8L8; // Some DDS writers assume the bitcount should be 8 instead of 16
+                }
             }
 
             if (16 == ddpf.RGBBitCount)
diff --git a/DirectXTex/DDS.h b/DirectXTex/DDS.h
index 8dc4f8e..4d715cc 100644
--- a/DirectXTex/DDS.h
+++ b/DirectXTex/DDS.h
@@ -160,6 +160,9 @@ DDSGLOBALCONST DDS_PIXELFORMAT DDSPF_A8L8 =
 DDSGLOBALCONST DDS_PIXELFORMAT DDSPF_A8L8_ALT =
     { sizeof(DDS_PIXELFORMAT), DDS_LUMINANCEA, 0, 8, 0x00ff, 0, 0, 0xff00 };
 
+DDSGLOBALCONST DDS_PIXELFORMAT DDSPF_A8L8_NVTT1 =
+    { sizeof(DDS_PIXELFORMAT), DDS_RGBA, 0, 16, 0x00ff, 0, 0, 0xff00 };
+
 DDSGLOBALCONST DDS_PIXELFORMAT DDSPF_A8 =
     { sizeof(DDS_PIXELFORMAT), DDS_ALPHA, 0, 8, 0, 0, 0, 0xff };
 
diff --git a/DirectXTex/DirectXTexDDS.cpp b/DirectXTex/DirectXTexDDS.cpp
index fda9333..9779284 100644
--- a/DirectXTex/DirectXTexDDS.cpp
+++ b/DirectXTex/DirectXTexDDS.cpp
@@ -104,6 +104,7 @@ namespace
         { DXGI_FORMAT_R16_UNORM,          CONV_FLAGS_NONE,        DDSPF_L16  }, // D3DFMT_L16
         { DXGI_FORMAT_R8G8_UNORM,         CONV_FLAGS_NONE,        DDSPF_A8L8 }, // D3DFMT_A8L8
         { DXGI_FORMAT_R8G8_UNORM,         CONV_FLAGS_NONE,        DDSPF_A8L8_ALT }, // D3DFMT_A8L8 (alternative bitcount)
+        { DXGI_FORMAT_R8G8_UNORM,         CONV_FLAGS_NONE,        DDSPF_A8L8_NVTT1 }, // D3DFMT_A8L8 (NVTT v1 wrote it with RGB instead of LUMINANCE)
 
         { DXGI_FORMAT_A8_UNORM,           CONV_FLAGS_NONE,        DDSPF_A8   }, // D3DFMT_A8