From 7a26f021c956b8804656e0a25944453c7dbfa1c3 Mon Sep 17 00:00:00 2001
From: un-pogaz <46523284+un-pogaz@users.noreply.github.com>
Date: Mon, 5 Jan 2026 14:43:09 +0100
Subject: [PATCH] improve dominant_color()

ensure to return the same value regardless of the size of the input image,
also improve performance
---
 src/calibre/utils/imageops/imageops.cpp | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/calibre/utils/imageops/imageops.cpp b/src/calibre/utils/imageops/imageops.cpp
index 7d11ac7a11..77d400fcd9 100644
--- a/src/calibre/utils/imageops/imageops.cpp
+++ b/src/calibre/utils/imageops/imageops.cpp
@@ -640,7 +640,17 @@ void overlay(const QImage &image, QImage &canvas, unsigned int left, unsigned in
 
 QColor dominant_color(const QImage &image) { // {{{
     if (image.isNull()) return QColor();
-    QImage img(image);
+    QImage img;
+    if (image.width() < 100 || image.height() < 100)
+        img = QImage(image);
+    else {
+        float ratio;
+        if (image.width() > image.height())
+            ratio = 100.0 / image.width();
+        else
+            ratio = 100.0 / image.height();
+        img = image.scaled(image.size() * ratio, Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
+    }
     ENSURE32(img);
     QHash<QRgb, int> colorCounts;
     const uchar* bits = img.constBits();