我有一个应用程序，屏幕中间有一个
QGraphicsView目前我已经重新实现了
QGraphicsViewvoid MyQGraphicsView::wheelEvent(QWheelEvent *event)
{
if(event->delta() > 0)
{
emit mouseWheelZoom(true);
}
else
{
emit mouseWheelZoom(false);
}
}
所以当我滚动时，如果鼠标滚轮向前，我会发出一个信号 true 如果鼠标滚轮向后，则发出 false 信号。
然后我将此信号连接到处理 GUI 内容的类中的插槽（缩放功能见下文）。现在基本上我认为我的缩放功能根本不是最好的方法，我已经看到了一些人们使用覆盖的wheelevent函数来设置比例的例子，但我真的找不到完整的答案。
所以我已经这样做了，但它无论如何都不完美，所以我正在寻找对此进行一些调整，或者寻找在滚轮事件函数中使用比例的工作示例。
我在构造函数中将
m_zoom_level0void 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);
}
}
正如您在上面看到的，我正在使用
QMatrix正如我所说，对此提供帮助或在鼠标下缩放的一个很好的例子会很棒。
这样的缩放有点棘手。让我分享我自己的课程来做到这一点。
标题：
#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;
}
使用示例：
Graphics_view_zoom* z = new Graphics_view_zoom(ui->graphicsView);
z->set_modifiers(Qt::NoModifier);
这是使用 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())
您只需使用内置功能
AnchorUnderMouseAnchorViewCentervoid SceneView::wheelEvent(QWheelEvent *event)
{
if (event->modifiers() & Qt::ControlModifier) {
// zoom
const ViewportAnchor anchor = transformationAnchor();
setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
int angle = event->angleDelta().y();
qreal factor;
if (angle > 0) {
factor = 1.1;
} else {
factor = 0.9;
}
scale(factor, factor);
setTransformationAnchor(anchor);
} else {
QGraphicsView::wheelEvent(event);
}
}
这是适合我的 python 版本。来自@Stefan Reinhardt 和@rengel 的答案的组合。
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())
这是上述解决方案的精简版本；只需将您需要放入轮子事件中的代码即可。 在我的测试中，无论有/没有滚动条，这都可以完美地工作;)
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;
}
有点晚了 但我今天只用 Pyside 经历了同样的事情，但应该是一样的......
方法“非常简单”，虽然花了我一些时间...... 首先将所有Anchor设置为NoAnchor，然后获取wheelevent的点，将其映射到场景中， 按此值平移场景，缩放，最后将其平移回来：
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())
这是唯一适合我的目的的解决方案。 恕我直言，这也是最合乎逻辑的解决方案......
经过多次挫折后，这似乎有效。问题似乎是
QGraphicsViewtransformQGraphicsView::mapToScene(const QPoint&) constmapToScene考虑到这一点，这就是有效的：记住鼠标指向的场景点，缩放，将该场景点映射到鼠标坐标，然后调整滚动条以使该点在鼠标下方结束：
void ZoomGraphicsView::wheelEvent(QWheelEvent* event)
{
const QPointF p0scene = mapToScene(event->pos());
qreal factor = std::pow(1.01, event->delta());
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());
}
更平滑的变焦
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());
}
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);
}
};
PyQt 回答得很好，这里提供了一个 C++ 函数，以备将来有人需要。
void CanvasView::zoomAt(const QPoint ¢erPos, 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);
}
绕点矩阵缩放公式：绕点旋转，与缩放相同。
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。因为缩放是使用鼠标失去焦点时的位置而不是当前位置来执行的。 （https://bugreports.qt.io/browse/QTBUG-73033）
2 - 当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，因此缩放也会像 #1 那样出现错误行为。 （https://bugreports.qt.io/browse/QTBUG-73067）。我制作了这个video，其中当我第二次单击窗口时，Chips 没有突出显示，因为没有调用 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 个芯片示例。我在here发布了此问题的解决方法。
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
Qt SDK 似乎没有对不常见场景（例如使用鼠标滚轮缩放）中的鼠标移动事件进行良好的测试。
将 @veslam:s 解决方案与 QT Wiki 中的 Smooth Zoom 代码 (https://wiki.qt.io/Smooth_Zoom_In_QGraphicsView) 相结合似乎效果很好：
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();
}
标题：
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();
};
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);
}
经过不断的调整，最终发现该方法表现最好：
def wheelEvent(self, e: QWheelEvent):
factor = 1.25 if e.angleDelta().y() > 0 else 0.8
zoom_origin = e.position().toPoint()
zoom_scene_origin = self.mapToScene(zoom_origin)
self.translate(zoom_scene_origin.x(), zoom_scene_origin.y())
self.scale(factor, factor)
delta = self.mapToScene(zoom_origin) - zoom_scene_origin
self.translate(delta.x(), delta.y())