From 5003d04e5987a78c8cf56b96b8d1ffbdf4c2feef Mon Sep 17 00:00:00 2001
From: Noah Davis <noahadvs@gmail.com>
Date: Sat, 4 Jul 2026 14:36:41 -0400
Subject: [PATCH] Remove OpenCV dependency

We don't have a reason to depend on OpenCV anymore
since KQuickImageEditor will no longer use it soon
and we don't really need to use a Lanczos filter.
This change should bring a measurable if not dramatic
improvement to startup time since a bicubic filter
(Qt::SmoothTransformation) has a simpler algorithm than
a Lanczos filter.
---
 CMakeLists.txt                      |  1 -
 src/CMakeLists.txt                  |  5 +-
 src/Platforms/ImagePlatformKWin.cpp | 28 +++------
 3 files changed, 10 insertions(+), 24 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0eea12dbf..fb0a8aa2f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -85,7 +85,6 @@ find_package(Wayland REQUIRED COMPONENTS Client)
 find_package(PlasmaWaylandProtocols REQUIRED)
 find_package(LayerShellQt REQUIRED)
 find_package(KPipeWire)
-find_package(OpenCV 4.7 REQUIRED core imgproc)
 find_package(PkgConfig REQUIRED)
 
 set_package_properties(KPipeWire PROPERTIES DESCRIPTION
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 953e72677..524c94b6f 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -93,11 +93,9 @@ ki18n_wrap_ui(spectacle
     Gui/SettingsDialog/VideoSaveOptions.ui
 )
 
-# Needed to compile with OpenCV
+# Needed to compile with Tesseract
 target_compile_options (spectacle PRIVATE -fexceptions)
 
-target_include_directories(spectacle PUBLIC ${OpenCV_INCLUDE_DIRS})
-
 target_link_libraries(spectacle PRIVATE
     Qt::Concurrent
     Qt::DBus
@@ -128,7 +126,6 @@ target_link_libraries(spectacle PRIVATE
     Wayland::Client
     LayerShellQt::Interface
     KQuickImageEditor
-    ${OpenCV_LIBRARIES}
     PkgConfig::TESSERACT
 )
 
diff --git a/src/Platforms/ImagePlatformKWin.cpp b/src/Platforms/ImagePlatformKWin.cpp
index 4521f0681..cd6a1e740 100644
--- a/src/Platforms/ImagePlatformKWin.cpp
+++ b/src/Platforms/ImagePlatformKWin.cpp
@@ -8,7 +8,6 @@
 #include "Config.h"
 #include "ExportManager.h"
 #include "Geometry.h"
-#include "QtCV.h"
 #include "DebugUtils.h"
 #include "ImageMetaData.h"
 
@@ -104,30 +103,21 @@ QImage combinedImage(const QList<QImage> &images)
     }
     // We ceil to the next integer size up so that integer DPR images are always crisp.
     const auto finalDpr = std::ceil(maxDpr);
-    // An RGBA8888 based format is needed for compatibility with OpenCV.
-    // If we used an ARGB32 based format, we'd need to swap red and blue.
-    // Not sure what to do if we end up having different formats for different screens.
     QImage finalImage{imageRect.size().toSize() * finalDpr, finalFormat};
     finalImage.fill(Qt::transparent);
-    auto mainMat = QtCV::qImageToMat(finalImage);
+    QPainter painter(&finalImage);
     for (auto &image : images) {
-        // Region Of Interest to put the image in the main image.
-        // Prevent ROI from going out of bounds or having negative size.
-        const auto rect = [finalDpr, &image, &finalImage] {
-            auto pos = ImageMetaData::logicalXY(image) * finalDpr;
-            auto size = image.deviceIndependentSize() * finalDpr;
-            auto rect = Geometry::rectClipped(QRectF(pos, size).toRect(), //
-                                              finalImage.rect());
-            return cv::Rect(rect.x(), rect.y(), rect.width(), rect.height());
-        }();
+        const auto pos = ImageMetaData::logicalXY(image) * finalDpr;
+        const auto size = (image.deviceIndependentSize() * finalDpr).toSize();
         const auto imageDpr = image.devicePixelRatio();
         const bool hasIntDpr = static_cast<int>(imageDpr) == imageDpr;
-        const auto interpolation = hasIntDpr ? cv::INTER_AREA : cv::INTER_LANCZOS4;
-        auto rgbaImage = image.format() == finalImage.format() ? image : image.convertedTo(finalFormat);
-        const auto mat = QtCV::qImageToMat(rgbaImage);
-        // Will just copy if there's no difference in size
-        cv::resize(mat, mainMat(rect), rect.size(), 0, 0, interpolation);
+        const auto interpolation = hasIntDpr ? Qt::FastTransformation : Qt::SmoothTransformation;
+        painter.drawImage(QRectF{pos, size},
+                          size == image.size() //
+                              ? image
+                              : image.scaled(size, Qt::KeepAspectRatio, interpolation));
     }
+    painter.end();
     finalImage.setDevicePixelRatio(finalDpr);
     ImageMetaData::setSubGeometryList(finalImage, geometryList);
     return finalImage;
--