Utils/ImageView/Inc/ImageView.h

#pragma once

#include <QGraphicsView>
#include <QImage>
#include <QPixmap>
#include <Qt>

class QLabel;
class QEvent;
class QGestureEvent;
class QGraphicsPixmapItem;
class QGraphicsScene;
class QMouseEvent;
class QPinchGesture;
class QWheelEvent;

// 可缩放、可平移的图片显示控件。
class ImageView : public QGraphicsView
{
    Q_OBJECT

public:
    explicit ImageView(QWidget* parent = nullptr);
    ~ImageView() override;

    void setImage(const QImage& image);
    void setImage(const QPixmap& pixmap);
    bool loadImage(const QString& filePath);
    void clearImage();

    bool hasImage() const;
    QImage image() const;

    // 比例以原始图片大小为基准，1.0 表示 100%。
    double zoomRatio() const;
    void setZoomRatio(double ratio);
    void zoomIn(double factor = 1.25);
    void zoomOut(double factor = 1.25);
    void resetView();

    void setZoomRange(double minimum, double maximum);
    double minimumZoomRatio() const;
    double maximumZoomRatio() const;

    // 图片未铺满视口时的停靠方向，默认居中。
    void setImageAlignment(Qt::Alignment alignment);
    Qt::Alignment imageAlignment() const;

signals:
    void imageChanged();
    void zoomRatioChanged(double ratio);

protected:
    bool viewportEvent(QEvent* event) override;
    void resizeEvent(QResizeEvent* event) override;
    void wheelEvent(QWheelEvent* event) override;
    void mousePressEvent(QMouseEvent* event) override;
    void mouseMoveEvent(QMouseEvent* event) override;
    void mouseReleaseEvent(QMouseEvent* event) override;
    void mouseDoubleClickEvent(QMouseEvent* event) override;

private:
    bool handleGestureEvent(QGestureEvent* event);
    void handlePinchGesture(QPinchGesture* gesture);
    void updateZoomLabel();
    void updateZoomRatio(double ratio, bool keepCenter);
    void updateZoomRatioAt(double ratio, const QPoint& viewportAnchor);
    void repositionZoomLabel();

    QGraphicsScene* m_scene;
    QGraphicsPixmapItem* m_pixmapItem;
    QLabel* m_zoomLabel;
    QImage m_image;
    double m_zoomRatio;
    double m_minimumZoomRatio;
    double m_maximumZoomRatio;
    Qt::Alignment m_imageAlignment;
    bool m_panning;
    bool m_pinching;
    bool m_needsInitialFit;
    double m_pinchStartZoomRatio;
    QPoint m_lastMousePosition;
};