Question

我的应用程序在屏幕中间有一个QGraphicsView窗口。我希望能够使用鼠标滚轮滚动放大和缩小。

目前我已经重新实现了QGraphicsView并覆盖了鼠标滚动功能，因此它不会滚动图像（就像默认情况下那样）。

void MyQGraphicsView::wheelEvent(QWheelEvent *event)
{
    if(event->delta() > 0)
    {
        emit mouseWheelZoom(true);
    }
    else
    {
        emit mouseWheelZoom(false);
    }
}

因此，当我滚动时，如果鼠标滚轮向前移动，如果鼠标滚轮前移，我发出的信号为真。

然后我将这个信号连接到处理我的GUI内容的类中的一个插槽（缩放功能见下面）。现在基本上我认为我的缩放功能根本不是最好的方法我已经看到一些人使用覆盖轮胎功能来设置尺度但我无法找到完整的答案。< / p>

所以相反，我已经做到了这一点，但它无论如何都不是完美的，所以我正在寻找这个稍微调整一下或者在轮子事件函数中使用比例的工作示例。

我在构造函数中初始化m_zoom_level到0。

void Display::zoomfunction(bool zoom)
{
    QMatrix matrix;

    if(zoom && m_zoom_level < 500)
    {
        m_zoom_level = m_zoom_level + 10;
        ui->graphicsView->setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
        matrix.scale(m_zoom_level, m_zoom_level);

        ui->graphicsView->setMatrix(matrix);
        ui->graphicsView->scale(1,-1);
    }
    else if(!zoom)
    {
        m_zoom_level = m_zoom_level - 10;
        ui->graphicsView->setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
        matrix.scale(m_zoom_level, m_zoom_level);

        ui->graphicsView->setMatrix(matrix);
        ui->graphicsView->scale(1,-1);
    }
}

正如您在上面所看到的，我使用QMatrix并将其缩放并将其设置为Graphicsview并将转换锚点设置为鼠标下方，但如果我＆＃39; m滚动加载它只会开始放大（我认为这与int循环或其他东西）。

正如我所说，帮助这个或者鼠标下的缩放比例很好。

Answer 1

这种缩放有点棘手。让我分享我自己的课程。

部首：

#include <QObject>
#include <QGraphicsView>

/*!
 * This class adds ability to zoom QGraphicsView using mouse wheel. The point under cursor
 * remains motionless while it's possible.
 *
 * Note that it becomes not possible when the scene's
 * size is not large enough comparing to the viewport size. QGraphicsView centers the picture
 * when it's smaller than the view. And QGraphicsView's scrolls boundaries don't allow to
 * put any picture point at any viewport position.
 *
 * When the user starts scrolling, this class remembers original scene position and
 * keeps it until scrolling is completed. It's better than getting original scene position at
 * each scrolling step because that approach leads to position errors due to before-mentioned
 * positioning restrictions.
 *
 * When zommed using scroll, this class emits zoomed() signal.
 *
 * Usage:
 *
 *   new Graphics_view_zoom(view);
 *
 * The object will be deleted automatically when the view is deleted.
 *
 * You can set keyboard modifiers used for zooming using set_modified(). Zooming will be
 * performed only on exact match of modifiers combination. The default modifier is Ctrl.
 *
 * You can change zoom velocity by calling set_zoom_factor_base().
 * Zoom coefficient is calculated as zoom_factor_base^angle_delta
 * (see QWheelEvent::angleDelta).
 * The default zoom factor base is 1.0015.
 */
class Graphics_view_zoom : public QObject {
  Q_OBJECT
public:
  Graphics_view_zoom(QGraphicsView* view);
  void gentle_zoom(double factor);
  void set_modifiers(Qt::KeyboardModifiers modifiers);
  void set_zoom_factor_base(double value);

private:
  QGraphicsView* _view;
  Qt::KeyboardModifiers _modifiers;
  double _zoom_factor_base;
  QPointF target_scene_pos, target_viewport_pos;
  bool eventFilter(QObject* object, QEvent* event);

signals:
  void zoomed();
};

来源：

#include "Graphics_view_zoom.h"
#include <QMouseEvent>
#include <QApplication>
#include <QScrollBar>
#include <qmath.h>

Graphics_view_zoom::Graphics_view_zoom(QGraphicsView* view)
  : QObject(view), _view(view)
{
  _view->viewport()->installEventFilter(this);
  _view->setMouseTracking(true);
  _modifiers = Qt::ControlModifier;
  _zoom_factor_base = 1.0015;
}

void Graphics_view_zoom::gentle_zoom(double factor) {
  _view->scale(factor, factor);
  _view->centerOn(target_scene_pos);
  QPointF delta_viewport_pos = target_viewport_pos - QPointF(_view->viewport()->width() / 2.0,
                                                             _view->viewport()->height() / 2.0);
  QPointF viewport_center = _view->mapFromScene(target_scene_pos) - delta_viewport_pos;
  _view->centerOn(_view->mapToScene(viewport_center.toPoint()));
  emit zoomed();
}

void Graphics_view_zoom::set_modifiers(Qt::KeyboardModifiers modifiers) {
  _modifiers = modifiers;

}

void Graphics_view_zoom::set_zoom_factor_base(double value) {
  _zoom_factor_base = value;
}

bool Graphics_view_zoom::eventFilter(QObject *object, QEvent *event) {
  if (event->type() == QEvent::MouseMove) {
    QMouseEvent* mouse_event = static_cast<QMouseEvent*>(event);
    QPointF delta = target_viewport_pos - mouse_event->pos();
    if (qAbs(delta.x()) > 5 || qAbs(delta.y()) > 5) {
      target_viewport_pos = mouse_event->pos();
      target_scene_pos = _view->mapToScene(mouse_event->pos());
    }
  } else if (event->type() == QEvent::Wheel) {
    QWheelEvent* wheel_event = static_cast<QWheelEvent*>(event);
    if (QApplication::keyboardModifiers() == _modifiers) {
      if (wheel_event->orientation() == Qt::Vertical) {
        double angle = wheel_event->angleDelta().y();
        double factor = qPow(_zoom_factor_base, angle);
        gentle_zoom(factor);
        return true;
      }
    }
  }
  Q_UNUSED(object)
  return false;
}

用法示例：

Graphics_view_zoom* z = new Graphics_view_zoom(ui->graphicsView);
z->set_modifiers(Qt::NoModifier);

Answer 2

以下是使用PyQt的解决方案：

def wheelEvent(self, event):
    """
    Zoom in or out of the view.
    """
    zoomInFactor = 1.25
    zoomOutFactor = 1 / zoomInFactor

    # Save the scene pos
    oldPos = self.mapToScene(event.pos())

    # Zoom
    if event.angleDelta().y() > 0:
        zoomFactor = zoomInFactor
    else:
        zoomFactor = zoomOutFactor
    self.scale(zoomFactor, zoomFactor)

    # Get the new position
    newPos = self.mapToScene(event.pos())

    # Move scene to old position
    delta = newPos - oldPos
    self.translate(delta.x(), delta.y())

Answer 3

这是python版本适合我。来自@Stefan Reinhardt和@rengel的答案组合。

class MyQGraphicsView(QtGui.QGraphicsView):

def __init__ (self, parent=None):
    super(MyQGraphicsView, self).__init__ (parent)

def wheelEvent(self, event):
    # Zoom Factor
    zoomInFactor = 1.25
    zoomOutFactor = 1 / zoomInFactor

    # Set Anchors
    self.setTransformationAnchor(QtGui.QGraphicsView.NoAnchor)
    self.setResizeAnchor(QtGui.QGraphicsView.NoAnchor)

    # Save the scene pos
    oldPos = self.mapToScene(event.pos())

    # Zoom
    if event.delta() > 0:
        zoomFactor = zoomInFactor
    else:
        zoomFactor = zoomOutFactor
    self.scale(zoomFactor, zoomFactor)

    # Get the new position
    newPos = self.mapToScene(event.pos())

    # Move scene to old position
    delta = newPos - oldPos
    self.translate(delta.x(), delta.y())

Answer 4

经过多次挫折之后，这似乎有效。问题似乎是QGraphicsView的{{1}}与其滚动位置无关，因此transform的行为取决于滚动位置和变换。我必须查看QGraphicsView::mapToScene(const QPoint&) const的来源才能理解这一点。

考虑到这一点，这是有用的：记住鼠标指向的场景点，缩放，将场景指向鼠标坐标，然后调整滚动条使该点在鼠标下方结束：

mapToScene

Answer 5

以上是上述解决方案的简要版本;只需要你需要放入轮子事件的代码。这在我的测试中使用/不使用滚动条，完美;）

void MyGraphicsView::wheelEvent(QWheelEvent* pWheelEvent)
{
    if (pWheelEvent->modifiers() & Qt::ControlModifier)
    {
        // Do a wheel-based zoom about the cursor position
        double angle = pWheelEvent->angleDelta().y();
        double factor = qPow(1.0015, angle);

        auto targetViewportPos = pWheelEvent->pos();
        auto targetScenePos = mapToScene(pWheelEvent->pos());

        scale(factor, factor);
        centerOn(targetScenePos);
        QPointF deltaViewportPos = targetViewportPos - QPointF(viewport()->width() / 2.0, viewport()->height() / 2.0);
        QPointF viewportCenter = mapFromScene(targetScenePos) - deltaViewportPos;
        centerOn(mapToScene(viewportCenter.toPoint()));

        return;
    }

Answer 6

有点晚了但是我今天只和Pyside一起走了同样的路，但应该是一样的......

这种方法非常简单＆＃34;尽管花了我一点时间...... 首先将所有锚点设置为NoAnchor，然后取出wheelevent的点，将其映射到场景，通过此值翻译场景，缩放并最终将其翻译回来：

def wheelEvent(self, evt):
    #Remove possible Anchors
    self.widget.setTransformationAnchor(QtGui.QGraphicsView.NoAnchor)
    self.widget.setResizeAnchor(QtGui.QGraphicsView.NoAnchor)
    #Get Scene Pos
    target_viewport_pos = self.widget.mapToScene(evt.pos())
    #Translate Scene
    self.widget.translate(target_viewport_pos.x(),target_viewport_pos.y())
    # ZOOM
    if evt.delta() > 0:
        self._eventHandler.zoom_ctrl(1.2)
    else:
        self._eventHandler.zoom_ctrl(0.83333)
    # Translate back
    self.widget.translate(-target_viewport_pos.x(),-target_viewport_pos.y())

这是唯一符合我目的的解决方案。恕我直言，这也是最合乎逻辑的解决方案......

Answer 7

您可以简单地使用内置功能model.add(Dense(50, input_dim= X_train.shape[1], weights = [np.zeros([692, 50]), np.zeros(50)]))或AnchorUnderMouse来保持鼠标或中心的焦点。这在Qt 5.7中适用于我

AnchorViewCenter

Answer 8

更平滑的缩放

void StatusView::wheelEvent(QWheelEvent * event)
{
    const QPointF p0scene = mapToScene(event->pos());

    qreal factor = qPow(1.2, event->delta() / 240.0);
    scale(factor, factor);

    const QPointF p1mouse = mapFromScene(p0scene);
    const QPointF move = p1mouse - event->pos(); // The move
    horizontalScrollBar()->setValue(move.x() + horizontalScrollBar()->value());
    verticalScrollBar()->setValue(move.y() + verticalScrollBar()->value());

}

Answer 9

将@veslam的解决方案与来自QT Wiki（https://wiki.qt.io/Smooth_Zoom_In_QGraphicsView）的Smooth Zoom代码相结合似乎非常有效：

来源：

QGraphicsViewMap::QGraphicsViewMap(QWidget *parent) : QGraphicsView(parent)
{
    setTransformationAnchor(QGraphicsView::NoAnchor);
    setResizeAnchor(QGraphicsView::NoAnchor);
}

void QGraphicsViewMap::wheelEvent(QWheelEvent* event)
{
    wheelEventMousePos = event->pos();

    int numDegrees = event->delta() / 8;
    int numSteps = numDegrees / 15; // see QWheelEvent documentation
    _numScheduledScalings += numSteps;
    if (_numScheduledScalings * numSteps < 0) // if user moved the wheel in another direction, we reset previously scheduled scalings
        _numScheduledScalings = numSteps;

    QTimeLine *anim = new QTimeLine(350, this);
    anim->setUpdateInterval(20);

    connect(anim, SIGNAL (valueChanged(qreal)), SLOT (scalingTime(qreal)));
    connect(anim, SIGNAL (finished()), SLOT (animFinished()));
    anim->start();
 }

void QGraphicsViewMap::scalingTime(qreal x)
{
    QPointF oldPos = mapToScene(wheelEventMousePos);

    qreal factor = 1.0+ qreal(_numScheduledScalings) / 300.0;
    scale(factor, factor);

    QPointF newPos = mapToScene(wheelEventMousePos);
    QPointF delta = newPos - oldPos;
    this->translate(delta.x(), delta.y());
}

void QGraphicsViewMap::animFinished()
{
    if (_numScheduledScalings > 0)
        _numScheduledScalings--;
    else
        _numScheduledScalings++;

    sender()->~QObject();
}

部首：

class QGraphicsViewMap : public QGraphicsView
{
    Q_OBJECT

private:
    qreal _numScheduledScalings = 0;
    QPoint wheelEventMousePos;
public:
    explicit QGraphicsViewMap(QWidget *parent = 0);

signals:

public slots:
    void wheelEvent(QWheelEvent* event);
    void scalingTime(qreal x);
    void animFinished();
};

Answer 10

在Mac OS上，使用QGraphicsView :: setTransformationAnchor（AnchorUnderMouse）时，此处引用的解决方案有时会失败：

1-当窗口没有焦点时，Qt不会更新lastMouseMoveScenePoint。因此，缩放是在失去焦点时使用鼠标位置执行的，而不是当前位置。（https://bugreports.qt.io/browse/QTBUG-73033）

2-使用任务控制切换窗口时，Qt有时会停止传播鼠标移动事件，因此缩放也像＃1中那样发生。（https://bugreports.qt.io/browse/QTBUG-73067）。我做了这个video，其中第二次单击窗口时未突出显示芯片，因为未调用mouseMoveEvent。我知道这不是我的应用程序中的错误，因为这是Qt提供的40000芯片示例。我发布了此问题here的解决方法。

3-setInteractive（false）不能与AnchorUnderMouse一起使用，因为用作变换中心的鼠标位置未更新：https://bugreports.qt.io/browse/QTBUG-60672

在不常见的情况下（例如，用鼠标滚轮缩放），似乎没有对Qt SDK的鼠标移动事件进行良好的测试。

Answer 11

简单的例子：

class CGraphicsVew : public QGraphicsView
{
    Q_OBJECT

protected:
    void wheelEvent(QWheelEvent *event)
    {
        qreal deltaScale = 1;
        deltaScale += event->delta() > 0 ? 0.1 : -0.1;
        setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
        scale(deltaScale, deltaScale);
    }
};

Answer 12



void GraphicsView::wheelEvent(QWheelEvent* event)
{
    switch (event->modifiers()) {
    case Qt::ControlModifier:
        if (event->angleDelta().x() != 0)
            QAbstractScrollArea::horizontalScrollBar()->setValue(QAbstractScrollArea::horizontalScrollBar()->value() - (event->delta()));
        else
            QAbstractScrollArea::verticalScrollBar()->setValue(QAbstractScrollArea::verticalScrollBar()->value() - (event->delta()));
        break;
    case Qt::ShiftModifier:
        QAbstractScrollArea::horizontalScrollBar()->setValue(QAbstractScrollArea::horizontalScrollBar()->value() - (event->delta()));
        break;
    case Qt::NoModifier:
        if (abs(event->delta()) == 120) {
            if (event->delta() > 0)
                zoomIn();
            else
                zoomOut();
        }
        break;
    default:
        QGraphicsView::wheelEvent(event);
        return;
    }
    event->accept();
}

const double zoomFactor = 1.5;

void GraphicsView::zoomIn()
{
    scale(zoomFactor, zoomFactor);
}

void GraphicsView::zoomOut()
{
    scale(1.0 / zoomFactor, 1.0 / zoomFactor);
}

void GraphicsView::wheelEvent(QWheelEvent* event) { switch (event->modifiers()) { case Qt::ControlModifier: if (event->angleDelta().x() != 0) QAbstractScrollArea::horizontalScrollBar()->setValue(QAbstractScrollArea::horizontalScrollBar()->value() - (event->delta())); else QAbstractScrollArea::verticalScrollBar()->setValue(QAbstractScrollArea::verticalScrollBar()->value() - (event->delta())); break; case Qt::ShiftModifier: QAbstractScrollArea::horizontalScrollBar()->setValue(QAbstractScrollArea::horizontalScrollBar()->value() - (event->delta())); break; case Qt::NoModifier: if (abs(event->delta()) == 120) { if (event->delta() > 0) zoomIn(); else zoomOut(); } break; default: QGraphicsView::wheelEvent(event); return; } event->accept(); } const double zoomFactor = 1.5; void GraphicsView::zoomIn() { scale(zoomFactor, zoomFactor); } void GraphicsView::zoomOut() { scale(1.0 / zoomFactor, 1.0 / zoomFactor); }

Answer 13

PyQt回答的效果很好，这里提供了一个c ++函数，以防将来有人需要。

void CanvasView::zoomAt(const QPoint &centerPos, double factor)
{
    //QGraphicsView::AnchorUnderMouse uses ::centerOn() in it's implement, which must need scroll.
    //transformationAnchor() default is AnchorViewCenter, you need set NoAnchor while change transform, 
    //and combine all transform change will work more effective
    QPointF targetScenePos = mapToScene(centerPos);
    ViewportAnchor oldAnchor = this->transformationAnchor();
    setTransformationAnchor(QGraphicsView::NoAnchor);

    QTransform matrix = transform();
    matrix.translate(targetScenePos.x(), targetScenePos.y())
            .scale(factor, factor)
            .translate(-targetScenePos.x(), -targetScenePos.y());
    setTransform(matrix);

    setTransformationAnchor(oldAnchor);
}

void CanvasView::wheelEvent(QWheelEvent *event)
{
    if(event->modifiers().testFlag(Qt::ControlModifier))
    {
        double angle = event->angleDelta().y();

        double factor = qPow(1.0015, angle);    //smoother zoom
        zoomAt(event->pos(), factor);
        return;
    }

    QGraphicsView::wheelEvent(event);
}

围绕点矩阵公式缩放rotate around point，与缩放相同。

QGraphicsView使用鼠标滚轮在鼠标位置放大和缩小

13 个答案: