From 1d0a762cdbee3bb75ac817593b51028db7cf34f3 Mon Sep 17 00:00:00 2001
From: Lucas CHOLLET <lucas.chollet@free.fr>
Date: Thu, 11 Jan 2024 22:34:39 -0500
Subject: [PATCH] LibGfx/TIFF: Add support for the IFD type

As described in the first edition of the TIFF technical notes, the IFD
type is identical to Long (UnsignedLong) except that it only contains
offset of valid IFDs.

https://www.awaresystems.be/imaging/tiff/specification/TIFFPM6.pdf
---
 Userland/Libraries/LibGfx/ImageFormats/TIFFLoader.cpp | 1 +
 Userland/Libraries/LibGfx/ImageFormats/TIFFLoader.h   | 4 ++++
 Userland/Libraries/LibGfx/TIFFGenerator.py            | 3 ++-
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/Userland/Libraries/LibGfx/ImageFormats/TIFFLoader.cpp b/Userland/Libraries/LibGfx/ImageFormats/TIFFLoader.cpp
index 2d829fff9a..1be3fff5d3 100644
--- a/Userland/Libraries/LibGfx/ImageFormats/TIFFLoader.cpp
+++ b/Userland/Libraries/LibGfx/ImageFormats/TIFFLoader.cpp
@@ -468,6 +468,7 @@ private:
         }
         case Type::UnsignedShort:
             return read_every_values.template operator()<u16>();
+        case Type::IFD:
         case Type::UnsignedLong:
             return read_every_values.template operator()<u32>();
         case Type::UnsignedRational:
diff --git a/Userland/Libraries/LibGfx/ImageFormats/TIFFLoader.h b/Userland/Libraries/LibGfx/ImageFormats/TIFFLoader.h
index f5e896fc61..99a1245b58 100644
--- a/Userland/Libraries/LibGfx/ImageFormats/TIFFLoader.h
+++ b/Userland/Libraries/LibGfx/ImageFormats/TIFFLoader.h
@@ -11,8 +11,12 @@
 
 namespace Gfx {
 
+// This is a link to the main TIFF specification from 1992
 // https://www.itu.int/itudoc/itu-t/com16/tiff-fx/docs/tiff6.pdf
 
+// First TIFF Technical notes from 1995
+// https://www.awaresystems.be/imaging/tiff/specification/TIFFPM6.pdf
+
 namespace TIFF {
 class TIFFLoadingContext;
 }
diff --git a/Userland/Libraries/LibGfx/TIFFGenerator.py b/Userland/Libraries/LibGfx/TIFFGenerator.py
index ec8af2871d..cc7e757bc2 100755
--- a/Userland/Libraries/LibGfx/TIFFGenerator.py
+++ b/Userland/Libraries/LibGfx/TIFFGenerator.py
@@ -40,6 +40,7 @@ class TIFFType(EnumWithExportName):
     SignedRational = 10, 8
     Float = 11, 4
     Double = 12, 8
+    IFD = 13, 4
     UTF8 = 129, 1
 
 
@@ -218,7 +219,7 @@ def tiff_type_to_cpp(t: TIFFType, with_promotion: bool = True) -> str:
         return 'ByteBuffer'
     if t == TIFFType.UnsignedShort:
         return 'u16'
-    if t == TIFFType.UnsignedLong:
+    if t == TIFFType.UnsignedLong or t == TIFFType.IFD:
         return 'u32'
     if t == TIFFType.UnsignedRational:
         return 'TIFF::Rational<u32>'