Make it so thumbnails abide by standard thumbnailer image resize rules.

src/kde.cpp

@@ -4,36 +4,57 @@
 #include <QImage>
 
 #include <KPluginFactory>
+#include <QPixmap>
+#include <QPainter>
 
 #include "common.h"
 
 K_PLUGIN_CLASS_WITH_JSON(VTFCreator, "../installer/kde/generated/plugin.json")
 
 KIO::ThumbnailResult VTFCreator::create(const KIO::ThumbnailRequest& request) {
-	// we only support local files
-	if (!request.url().isLocalFile()) {
-		return KIO::ThumbnailResult::fail();
-	}
-	// create the thumbnail data
-	int targetWidth = request.targetSize().width();
-	int targetHeight = request.targetSize().height();
-	auto image = createThumbnail(
-	        request.url().toLocalFile().toUtf8().data(),
-	        targetWidth,
-	        targetHeight);
-	if (image.empty()) {
-		return KIO::ThumbnailResult::fail();
-	}
-	// convert to required format
-	const auto img = QImage{
-		reinterpret_cast<unsigned char*>(image.data()),
-		targetWidth,
-		targetHeight,
-		QImage::Format_RGBA8888,
-	}.convertToFormat(QImage::Format_ARGB32_Premultiplied);
-
-	// done!
-	return !img.isNull() ? KIO::ThumbnailResult::pass(img) : KIO::ThumbnailResult::fail();
+    // we only support local files
+    if (!request.url().isLocalFile()) {
+        return KIO::ThumbnailResult::fail();
+    }
+    // create the thumbnail data
+    int targetWidth = request.targetSize().width();
+    int targetHeight = request.targetSize().height();
+
+    int vtfWidth = 0;
+    int vtfHeight = 0;
+
+    auto image = createThumbnail(
+            request.url().toLocalFile().toUtf8().data(),
+            vtfWidth,
+            vtfHeight);
+
+    if (image.empty()) {
+        return KIO::ThumbnailResult::fail();
+    }
+    // convert to required format
+    const auto img = QImage{
+            reinterpret_cast<unsigned char*>(image.data()),
+            vtfWidth,
+            vtfHeight,
+            QImage::Format_RGBA8888,
+    };
+
+    auto imgPX = QPixmap(targetWidth,targetHeight);
+
+    const auto scaledImage = img.scaled(targetWidth,targetHeight, Qt::KeepAspectRatio);
+    imgPX.fill({0,0,0,0});
+    auto painter = QPainter(&imgPX);
+    painter.setBackground(QColor{0,0,0,0});
+    auto heightResult = targetHeight - scaledImage.height();
+    auto widthResult = targetWidth - scaledImage.width();
+
+    painter.setCompositionMode(QPainter::CompositionMode_SourceOver);
+    painter.drawImage(static_cast<int>(static_cast<float>(widthResult) * 0.5),static_cast<int>(static_cast<float>(heightResult) * 0.5) ,scaledImage);
+
+    const auto img2 = imgPX.toImage().convertToFormat(QImage::Format_ARGB32_Premultiplied);
+
+    // done!
+    return !img2.isNull() ? KIO::ThumbnailResult::pass(img2) : KIO::ThumbnailResult::fail();
 }
 
 #include <kde.moc>