From 78a8081f2cbd91b8bc206b4a0f2b42322230aede Mon Sep 17 00:00:00 2001
From: Benjamin Grimm-Lebsanft <benjamin@lebsanft.org>
Date: Wed, 24 Jun 2026 10:42:07 +0200
Subject: [PATCH] Support Canon Highlight Tone Priority compensation

---
 src/common/exif.cc | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/common/exif.cc b/src/common/exif.cc
index 6fd7b862ebcb..12a7873b65f6 100644
--- a/src/common/exif.cc
+++ b/src/common/exif.cc
@@ -1172,6 +1172,13 @@ static void _check_highlight_preservation(Exiv2::ExifData &exifData,
        else if(state == 2)
           img->exif_highlight_preservation = 0.66f;     // estimated strength for Strong
     }
+    // Canon Highlight Tone Priority. D+ (1) and D+2 (2) both apply ~1 EV sensor underexposure.
+    if(FIND_EXIF_TAG("Exif.CanonLiOp.HighlightTonePriority"))
+    {
+       const long state = pos->toLong(0);
+       if(state > 0)
+          img->exif_highlight_preservation += 1.0f; 
+    }
     else if(FIND_EXIF_TAG("Exif.Fujifilm.DevelopmentDynamicRange")  // manual mode DR100/DR200/DR400
        || FIND_EXIF_TAG("Exif.Fujifilm.AutoDynamicRange"))	    // auto mode
     {