C++ QT 圖片查看組件記錄

  • 頭文件
#ifndef IMAGEVIEWWIDGET_HPP
#define IMAGEVIEWWIDGET_HPP

#include <QWidget>
#include <QPixmap>
#include <QPainter>
#include <QWheelEvent>
#include <QResizeEvent>


class ImageViewWidget : public QWidget
{
    Q_OBJECT

public:
    explicit ImageViewWidget(QWidget* parrent = nullptr);
    ~ImageViewWidget();

    // 加載圖片
    bool loadImage(const QString& image_path);
    // 設(shè)置pixmap
    void setPixmap(const QPixmap& pixmap);
    // 獲取pixmap
    QPixmap pixmap() const;

    // 放大
    void zoomIn(double factor = 1.1);
    // 縮小
    void zoomOut(double factor = 0.9);
    // 重置
    void resetZoom();
    // 適應(yīng)窗口
    void fitToWindow();
    // 獲取當(dāng)前縮放比例
    double getScaleFactor() const;

protected:
    void paintEvent(QPaintEvent* event) override;
    void resizeEvent(QResizeEvent* event) override;
    void wheelEvent(QWheelEvent* evennt) override;
    void mousePressEvent(QMouseEvent* event) override;
    void mouseMoveEvent(QMouseEvent *event) override;
    void mouseReleaseEvent(QMouseEvent *event) override;

private:
    QPixmap m_original_pixmap;
    QPixmap m_scaled_pixmap;
    double  m_scaled_factor;
    bool    m_is_dragging;
    QPoint  m_last_mouse_point;
    QPointF m_image_offset;

    void updateScaledPixmap();
    void adjustOffset();

};

#endif // IMAGEVIEWWIDGET_HPP
  • 實(shí)現(xiàn)文件
#include "ImageViewWidget.hpp"

#include <QPainter>
#include <QDebug>
#include <QGuiApplication>


ImageViewWidget::ImageViewWidget(QWidget* parrent):QWidget(parrent), m_scaled_factor(1.0), m_is_dragging(false)
{

}

ImageViewWidget::~ImageViewWidget()
{
}

void ImageViewWidget::paintEvent(QPaintEvent *event)
{
    Q_UNUSED(event);
    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing, true);
    painter.setRenderHint(QPainter::SmoothPixmapTransform, true);

    if (m_scaled_pixmap.isNull()) {
        painter.drawText(rect(), Qt::AlignCenter, tr("No Image Loaded"));
        return;
    }
    int x = (width() - m_scaled_pixmap.width()) / 2 + m_image_offset.x();
    int y = (height() - m_scaled_pixmap.height()) / 2 + m_image_offset.y();

    painter.drawPixmap(x, y, m_scaled_pixmap);
}

void ImageViewWidget::resizeEvent(QResizeEvent *event)
{
    Q_UNUSED(event);
    if (!m_original_pixmap.isNull()) {
        updateScaledPixmap();
        adjustOffset();
        update();
    }
}

void ImageViewWidget::wheelEvent(QWheelEvent *event)
{
    if (m_original_pixmap.isNull()) {
        event->ignore();
        return;
    }

    int angleDelta = event->angleDelta().y();
    QPointF mousePosInWidget = event->position();
    QPointF imageTopLeftInWidget((width() - m_scaled_pixmap.width()) / 2.0 + m_image_offset.x(),
                                 (height() - m_scaled_pixmap.height()) / 2.0 + m_image_offset.y());
    QPointF mousePosOnImage = (mousePosInWidget - imageTopLeftInWidget) / m_scaled_factor;


    if (angleDelta > 0) {
        zoomIn();
    } else if (angleDelta < 0) {
        zoomOut();
    }

    QPointF newImageTopLeftInWidget = mousePosInWidget - (mousePosOnImage * m_scaled_factor);
    m_image_offset.setX(newImageTopLeftInWidget.x() - (width() - m_original_pixmap.width() * m_scaled_factor) / 2.0);
    m_image_offset.setY(newImageTopLeftInWidget.y() - (height() - m_original_pixmap.height() * m_scaled_factor) / 2.0);


    adjustOffset();
    updateScaledPixmap();
    update();
    event->accept();
}

void ImageViewWidget::mousePressEvent(QMouseEvent* event)
{
    if (event->button() == Qt::LeftButton && !m_original_pixmap.isNull())
    {
        m_is_dragging = true;
        m_last_mouse_point = event->pos();
        setCursor(Qt::ClosedHandCursor);
        event->accept();
    } else {
        event->ignore(); // 如果不是左鍵或者沒(méi)有圖片，則忽略事件
    }
}

void ImageViewWidget::mouseMoveEvent(QMouseEvent *event)
{
    if (m_is_dragging && (event->buttons() & Qt::LeftButton))
    {
        QPoint current_mouse_pos = event->pos();
        QPointF delta = current_mouse_pos - m_last_mouse_point;
        m_image_offset += delta;

        m_last_mouse_point = current_mouse_pos;

        adjustOffset();
        update();
        event->accept();
    } else {
        event->ignore();
    }
}

void ImageViewWidget::mouseReleaseEvent(QMouseEvent *event)
{
    if (event->button() == Qt::LeftButton && m_is_dragging)
    {
        m_is_dragging = false;
        setCursor(Qt::ArrowCursor);
        event->accept();
    }
    else
    {
        event->ignore();
    }
}

bool ImageViewWidget::loadImage(const QString &image_path)
{
    QPixmap new_pixmap(image_path);
    if(new_pixmap.isNull())
    {
        qWarning() << "Failed to load image:" << image_path;
        m_original_pixmap = QPixmap();
        m_scaled_pixmap = QPixmap();
        m_scaled_factor = 1.0;
        m_image_offset = QPointF(0,0);
        update();
        return false;
    }
    setPixmap(new_pixmap);
    return true;
}

QPixmap ImageViewWidget::pixmap() const
{
    return m_original_pixmap;
}

void ImageViewWidget::setPixmap(const QPixmap &pixmap)
{
    m_original_pixmap = pixmap;
    m_scaled_pixmap = m_original_pixmap.scaled(
        m_original_pixmap.size() * m_scaled_factor,
        Qt::KeepAspectRatio,
        Qt::SmoothTransformation
    );
    m_image_offset = QPointF(0, 0);
    fitToWindow();
}

double ImageViewWidget::getScaleFactor() const
{
    return m_scaled_factor;
}

void ImageViewWidget::fitToWindow()
{
    if (m_original_pixmap.isNull() || width() == 0 || height() == 0) {
        m_scaled_factor = 1.0;
        updateScaledPixmap();
        update();
        return;
    }

    double wRatio = (double)width() / m_original_pixmap.width();
    double hRatio = (double)height() / m_original_pixmap.height();
    m_scaled_factor = qMin(wRatio, hRatio);
    m_image_offset = QPointF(0,0);
    updateScaledPixmap();
    update();
}

void ImageViewWidget::zoomIn(double factor)
{
    if (m_original_pixmap.isNull())
    {
        return;
    }
    m_scaled_factor *= factor;
    updateScaledPixmap();
    update();
}


void ImageViewWidget::zoomOut(double factor)
{
    if (m_original_pixmap.isNull()) return;
    m_scaled_factor *= factor;
    if (m_scaled_factor < 0.01) m_scaled_factor = 0.01;
    updateScaledPixmap();
    update();
}

void ImageViewWidget::resetZoom()
{
    if (m_original_pixmap.isNull()) return;
    m_scaled_factor = 1.0;
    m_image_offset = QPointF(0,0);
    updateScaledPixmap();
    update();
}


void ImageViewWidget::updateScaledPixmap()
{
    if (m_original_pixmap.isNull())
    {
        if (!m_scaled_pixmap.isNull())
        {
            m_scaled_pixmap = QPixmap();
        }
        return;
    }

    if (m_scaled_factor <= 0) {
        qWarning() << "updateScaledPixmap: Invalid scale factor " << m_scaled_factor << ". Using 1.0 instead.";
        m_scaled_factor = 1.0; // Or some other sensible default / minimum
    }
    // 根據(jù) m_scaleFactor 縮放原始圖片
    // 使用 Qt::SmoothTransformation 來(lái)獲得更好的縮放質(zhì)量
    m_scaled_pixmap = m_original_pixmap.scaled(
        m_original_pixmap.size() * m_scaled_factor,
        Qt::KeepAspectRatio,
        Qt::SmoothTransformation
        );
    adjustOffset();
}

void ImageViewWidget::adjustOffset()
{
    if (m_scaled_pixmap.isNull()) return;

    QRectF imageRectInWidget(
        (width() - m_scaled_pixmap.width()) / 2.0 + m_image_offset.x(),
        (height() - m_scaled_pixmap.height()) / 2.0 + m_image_offset.y(),
        m_scaled_pixmap.width(),
        m_scaled_pixmap.height()
        );

    QRectF widgetRect(0,0, width(), height());


    if (m_scaled_pixmap.width() < width())
    {
        double allowableXOffset = (width() - m_scaled_pixmap.width()) / 2.0;
        m_image_offset.setX(qBound(-allowableXOffset, m_image_offset.x(), allowableXOffset));
    }
    else
    {
        double minXOffset = width() - m_scaled_pixmap.width() - (width() - m_scaled_pixmap.width()) / 2.0;
        double maxXOffset = -(width() - m_scaled_pixmap.width()) / 2.0;
        m_image_offset.setX(qBound(minXOffset, m_image_offset.x(), maxXOffset));
    }

    if (m_scaled_pixmap.height() < height())
    {
        double allowableYOffset = (height() - m_scaled_pixmap.height()) / 2.0;
        m_image_offset.setY(qBound(-allowableYOffset, m_image_offset.y(), allowableYOffset));
    }
    else
    {
        double minYOffset = height() - m_scaled_pixmap.height() - (height() - m_scaled_pixmap.height()) / 2.0;
        double maxYOffset = -(height() - m_scaled_pixmap.height()) / 2.0;
        m_image_offset.setY(qBound(minYOffset, m_image_offset.y(), maxYOffset));
    }
}
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