[libcamera-devel] [PATCH v2] qcam: viewfinder: Maintain aspect ratio

[Kieran Bingham]

Keep the image aspect ratio when displaying in the viewfinder.

When the window is adjusted to a size that differs in aspect ratio to
the image, keep the image centered in the main viewpoint.

Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
---

v2: (fixed up from Laurent's review comments)

 - No longer accept event on an invalid size.
 - centering simplifed


 src/qcam/viewfinder_qt.cpp | 16 ++++++++++++++--
 src/qcam/viewfinder_qt.h   |  2 ++
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/qcam/viewfinder_qt.cpp b/src/qcam/viewfinder_qt.cpp
index e436714c6bdb..08ac29e9fa99 100644
--- a/src/qcam/viewfinder_qt.cpp
+++ b/src/qcam/viewfinder_qt.cpp
@@ -15,6 +15,7 @@
 #include <QMap>
 #include <QMutexLocker>
 #include <QPainter>
+#include <QResizeEvent>
 #include <QtDebug>
 
 #include <libcamera/formats.h>
@@ -34,7 +35,7 @@ static const QMap<libcamera::PixelFormat, QImage::Format> nativeFormats
 };
 
 ViewFinderQt::ViewFinderQt(QWidget *parent)
-	: QWidget(parent), buffer_(nullptr)
+	: QWidget(parent), place_(rect()), buffer_(nullptr)
 {
 	icon_ = QIcon(":camera-off.svg");
 }
@@ -146,7 +147,7 @@ void ViewFinderQt::paintEvent(QPaintEvent *)
 
 	/* If we have an image, draw it. */
 	if (!image_.isNull()) {
-		painter.drawImage(rect(), image_, image_.rect());
+		painter.drawImage(place_, image_, image_.rect());
 		return;
 	}
 
@@ -179,3 +180,14 @@ QSize ViewFinderQt::sizeHint() const
 {
 	return size_.isValid() ? size_ : QSize(640, 480);
 }
+
+void ViewFinderQt::resizeEvent(QResizeEvent *event)
+{
+	if (!size_.isValid())
+		return;
+
+	place_.setSize(size_.scaled(event->size(), Qt::KeepAspectRatio));
+	place_.moveCenter(rect().center());
+
+	event->accept();
+}
diff --git a/src/qcam/viewfinder_qt.h b/src/qcam/viewfinder_qt.h
index d755428887c0..bf31b81b3437 100644
--- a/src/qcam/viewfinder_qt.h
+++ b/src/qcam/viewfinder_qt.h
@@ -42,6 +42,7 @@ Q_SIGNALS:
 
 protected:
 	void paintEvent(QPaintEvent *) override;
+	void resizeEvent(QResizeEvent *) override;
 	QSize sizeHint() const override;
 
 private:
@@ -49,6 +50,7 @@ private:
 
 	libcamera::PixelFormat format_;
 	QSize size_;
+	QRect place_;
 
 	/* Camera stopped icon */
 	QSize vfSize_;
-- 
2.25.1