QGraphicsItem resize with mouse position and keeping aspect ratio - image

Question

took the code from the one other forum. This code makes resizeble rectangles. I corrected a little for displaying pictures.
if anyone knows, tell me how to calculate the position of the MovableCircle so that the initial aspect ratio is preserved.
I've implemented part of the algorithm for eBottomRight and eTopLeft, but it still works very bad and doesn't work for BottomLeft and TopRight points. I want that it will be look like Krita or PureRef resize behaviour.
Thanks for any help, regards max
this example gif: https://media.giphy.com/media/7XBNv61efV7S9DbgJO/giphy.gif
calc part:
void MovableCircle::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
auto pos = mapToScene(event->pos() + _shiftMouseCoords);
qreal xl = (pos.x() == 0) ? .1 : pos.x();
qreal yl = (pos.y() == 0) ? .1 : pos.y();
qreal arl = qAbs(xl / yl);
if (circlePos_ == eBottomRight) {
if (arl > aspectRatio_) {
pos.setX(yl * aspectRatio_);
} else {
pos.setY(xl / aspectRatio_);
}
}
if (circlePos_ == eTopLeft) {
LOG_WARNING(logger, "Circle Pos: ", circlePos_, ", ", pos.x(), " ", pos.y());
LOG_WARNING(logger, "Init Aspect Ratio: ", aspectRatio_, ", Current AspectRatio:", arl);
if (arl > aspectRatio_) {
LOG_DEBUG(logger, "> Before: ", pos.x(), ", ", pos.y());
pos.setY(xl / aspectRatio_);
LOG_DEBUG(logger, "> After: ", pos.x(), ", ", pos.y());
} else {
LOG_DEBUG(logger, "< Before: ", pos.x(), ", ", pos.y());
pos.setX(yl * aspectRatio_);
LOG_DEBUG(logger, "< After: ", pos.x(), ", ", pos.y());
}
}
setPos(pos);
emit circleMoved();
}
MovableCircle class:
class MovableCircle : public QGraphicsObject
{
Q_OBJECT
public:
enum ECirclePos {
eTopLeft = 0,
eTopRight,
eBottomRight,
eBottomLeft,
};
explicit MovableCircle(ECirclePos cp, double ar, QGraphicsItem *parent = 0);
private:
QRectF boundingRect() const;
QPainterPath shape() const;
void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
void mouseMoveEvent(QGraphicsSceneMouseEvent *event);
void mousePressEvent(QGraphicsSceneMouseEvent *event);
void mouseReleaseEvent(QGraphicsSceneMouseEvent *event);
QPointF _shiftMouseCoords;
private:
double aspectRatio_;
ECirclePos circlePos_;
signals:
void circleMoved();
};
MovableCircle::MovableCircle(ECirclePos cp, double ar, QGraphicsItem *parent) :
QGraphicsObject(parent), aspectRatio_(ar), circlePos_(cp)
{
setFlag(ItemClipsToShape, true);
setCursor(QCursor(Qt::PointingHandCursor));
}
QRectF MovableCircle::boundingRect() const
{
qreal adjust = 0.5;
return QRectF(-5 - adjust, -5 - adjust,
10 + adjust, 10 + adjust);
}
QPainterPath MovableCircle::shape() const
{
QPainterPath path;
qreal adjust = 0.5;
path.addEllipse(-5 - adjust, -5 - adjust,
10 + adjust, 10 + adjust);
return path;
}
void MovableCircle::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
Q_UNUSED(option);
Q_UNUSED(widget);
painter->setBrush(QBrush(QColor(0, 160, 230)));
painter->setPen(QPen(QColor(0, 160, 230)));
painter->drawEllipse(-5, -5, 10, 10);
}
void MovableCircle::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
_shiftMouseCoords = this->pos() - mapToScene(event->pos());
this->setCursor(QCursor(Qt::ClosedHandCursor));
}
void MovableCircle::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
auto pos = mapToScene(event->pos() + _shiftMouseCoords);
qreal xl = (pos.x() == 0) ? .1 : pos.x();
qreal yl = (pos.y() == 0) ? .1 : pos.y();
qreal arl = qAbs(xl / yl);
if (circlePos_ == eBottomRight) {
if (arl > aspectRatio_) {
pos.setX(yl * aspectRatio_);
} else {
pos.setY(xl / aspectRatio_);
}
}
if (circlePos_ == eTopLeft) {
if (arl > aspectRatio_) {
pos.setY(xl / aspectRatio_);
} else {
pos.setX(yl * aspectRatio_);
}
}
setPos(pos);
emit circleMoved();
}
void MovableCircle::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
{
Q_UNUSED(event);
this->setCursor(QCursor(Qt::PointingHandCursor));
}
MoveItem class:
class MoveItem : public QObject, public QGraphicsItem//public QGraphicsObject
{
Q_OBJECT
Q_INTERFACES(QGraphicsItem)
public:
explicit MoveItem(uint64_t& zc, QGraphicsItem *parent = 0);
~MoveItem();
signals:
protected:
QRectF boundingRect() const override;
void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) override;
void mouseMoveEvent(QGraphicsSceneMouseEvent *event) override;
void mousePressEvent(QGraphicsSceneMouseEvent *event) override;
void mouseReleaseEvent(QGraphicsSceneMouseEvent *event) override;
void wheelEvent(QGraphicsSceneWheelEvent *event) override;
void hoverEnterEvent(QGraphicsSceneHoverEvent *event) override;
void hoverLeaveEvent(QGraphicsSceneHoverEvent *event) override;
void hoverMoveEvent(QGraphicsSceneHoverEvent *event) override;
private:
QPointF shiftMouseCoords_;
QImage qimage_;
QPixmap pixmap_;
uint64_t& zCounter_;
MovableCircle *_topLeftCircle, *_topRightCircle, *_bottomLeftCircle, *_bottomRightCircle;
QSizeF _size;
QRectF rect_;
public slots:
};
MoveItem::MoveItem(uint64_t& zc, QGraphicsItem *parent) :
QGraphicsItem(parent), zCounter_(zc)
{
setZValue(zCounter_);
qimage_ = QImage("kot.png");
pixmap_ = QPixmap::fromImage(qimage_);
_size = pixmap_.size();
rect_ = qimage_.rect();
setAcceptHoverEvents(true);
setFlag(QGraphicsItem::ItemIsMovable, true);
double ar = _size.width() / _size.height();
// Top Left
_topLeftCircle = new MovableCircle(MovableCircle::eTopLeft, ar, this);
_topLeftCircle->setPos(0, 0);
// Top Right
_topRightCircle = new MovableCircle(MovableCircle::eTopRight, ar, this);
_topRightCircle->setPos(_size.width(), 0);
// Bottom Right
_bottomRightCircle = new MovableCircle(MovableCircle::eBottomRight, ar, this);
_bottomRightCircle->setPos(_size.width(), _size.height());
// Bottom Left
_bottomLeftCircle = new MovableCircle(MovableCircle::eBottomLeft, ar, this);
_bottomLeftCircle->setPos(0, _size.height());
// Signals
// If a delimiter point has been moved, so force the item to redraw
connect(_topLeftCircle, &MovableCircle::circleMoved, this, [this](){
_bottomLeftCircle->setPos( _topLeftCircle->pos().x(), _bottomLeftCircle->pos().y());
_topRightCircle->setPos(_topRightCircle->pos().x(), _topLeftCircle->pos().y());
update(); // force to Repaint
});
connect(_topRightCircle, &MovableCircle::circleMoved, this, [this](){
_topLeftCircle->setPos(_topLeftCircle->pos().x(), _topRightCircle->pos().y());
_bottomRightCircle->setPos(_topRightCircle->pos().x(), _bottomRightCircle->pos().y());
update(); // force to Repaint
});
connect(_bottomLeftCircle, &MovableCircle::circleMoved, this, [this](){
_topLeftCircle->setPos(_bottomLeftCircle->pos().x(), _topLeftCircle->pos().y());
_bottomRightCircle->setPos(_bottomRightCircle->pos().x(), _bottomLeftCircle->pos().y());
update(); // force to Repaint
});
connect(_bottomRightCircle, &MovableCircle::circleMoved, this, [this](){
_bottomLeftCircle->setPos(_bottomLeftCircle->pos().x(), _bottomRightCircle->pos().y());
_topRightCircle->setPos(_bottomRightCircle->pos().x(), _topRightCircle->pos().y());
update(); // force to Repaint
});
}
MoveItem::~MoveItem()
{
}
QRectF MoveItem::boundingRect() const
{
qreal distX = sqrt(pow(_topLeftCircle->x() - _topRightCircle->x(),2) +
pow(_topLeftCircle->y() - _topRightCircle->y(),2)); // eucledian distance
qreal distY = sqrt(pow(_topLeftCircle->x() - _bottomLeftCircle->x(),2) +
pow(_topLeftCircle->y() - _bottomLeftCircle->y(),2)); // eucledian distance
return QRectF(qMin(_topLeftCircle->pos().x(), _topRightCircle->pos().x()) ,
qMin(_topLeftCircle->pos().y(), _bottomLeftCircle->pos().y()),
distX, distY);
}
void MoveItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
painter->drawImage(boundingRect(), qimage_);
painter->setPen(QPen(QColor(0, 160, 230),2));
painter->drawRect(boundingRect());
Q_UNUSED(widget);
}
void MoveItem::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
this->setPos(mapToScene(event->pos()+ shiftMouseCoords_));
}
void MoveItem::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
setZValue(++zCounter_);
shiftMouseCoords_ = (this->pos() - mapToScene(event->pos()))/scale();
if (event->button() == Qt::LeftButton) {
if (event->modifiers() == Qt::ShiftModifier) {
} else {
QGraphicsItem::mousePressEvent(event);
}
}
}
void MoveItem::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
{
if (event->button() == Qt::LeftButton) {
if (event->modifiers() == Qt::ShiftModifier) {
} else {
QGraphicsItem::mousePressEvent(event);
}
}
}

Answer 1

I found a solution using vector math.(thanks to my colleague Dima Chernikov)
ABCD - our picture.
K' - cursor point.
D2 - the point we are looking for(new position of D)
gif example: https://media.giphy.com/media/uffXKjNNy5ykzpvsR2/giphy.gif
(circlePos_ == eBottomLeft) in code
code: (I will most likely redo it later using templates. but now it is more clear for understanding)
void MovableCircle::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
auto pos = mapToScene(event->pos() + _shiftMouseCoords);
qreal xl = pos.x();
qreal yl = pos.y();
auto rect = parentItem()->boundingRect();
QPointF a(rect.x(), rect.y());
QPointF b(rect.x() + rect.width(), rect.y());
QPointF c(rect.x() + rect.width(), rect.y() + rect.height());
QPointF d(rect.x(), rect.y() + rect.height());
if (circlePos_ == eTopRight) {
Vec2d dc(c.x()-d.x(), c.y()-d.y());
Vec2d cb(b.x()-c.x(), b.y()-c.y());
Vec2d db(b.x()-d.x(), b.y()-d.y());
Vec2d dk(pos.x()-d.x(), pos.y()-d.y());
auto dc_len = dc.length();
auto cb_len = cb.length();
auto db_len = db.length();
auto dk_len = dk.length();
auto dkdb_dot = Vec2d<qreal>::dot(db, dk);
auto cos_kdb = dkdb_dot/(db_len*dk_len);
auto dd2_len = dk_len * cos_kdb;
auto x =(dd2_len * dc_len) / (std::sqrt(cb_len * cb_len + dc_len * dc_len));
auto y = std::sqrt(dd2_len * dd2_len - x * x);
if (x < 10 || y < 10) return;
pos.setX(d.x()+x);
pos.setY(d.y()-y);
}
if (circlePos_ == eBottomRight) {
Vec2d ad(d.x()-a.x(), d.y()-a.y());
Vec2d dc(c.x()-d.x(), c.y()-d.y());
Vec2d ac(c.x()-a.x(), c.y()-a.y());
Vec2d ak(pos.x()-a.x(), pos.y()-a.y());
auto ad_len = ad.length();
auto dc_len = dc.length();
auto ac_len = ac.length();
auto ak_len = ak.length();
auto akac_dot = Vec2d<qreal>::dot(ac, ak);
auto cos_kac = akac_dot/(ac_len*ak_len);
auto ad2_len = ak_len * cos_kac;
auto x =(ad2_len * dc_len) / (std::sqrt(ad_len * ad_len + dc_len * dc_len));
auto y = std::sqrt(ad2_len * ad2_len - x * x);
if (x < 10 || y < 10) return;
pos.setX(a.x()+x);
pos.setY(a.y()+y);
}
if (circlePos_ == eTopLeft) {
qDebug()<<this->parentItem()->boundingRect();
Vec2d cb(b.x()-c.x(), b.y()-c.y());
Vec2d ba(a.x()-b.x(), a.y()-b.y());
Vec2d ca(a.x()-c.x(), a.y()-c.y());
Vec2d ck(pos.x()-c.x(), pos.y()-c.y());
auto cb_len = cb.length();
auto ba_len = ba.length();
auto ca_len = ca.length();
auto ck_len = ck.length();
auto ckca_dot = Vec2d<qreal>::dot(ca, ck);
auto cos_kca = ckca_dot/(ca_len*ck_len);
auto cd2_len = ck_len * cos_kca;
auto y =(cd2_len * cb_len) / (std::sqrt(ba_len * ba_len + cb_len * cb_len));
auto x = std::sqrt(cd2_len * cd2_len - y * y);
if (x < 10 || y < 10) return;
pos.setX(c.x()-x);
pos.setY(c.y()-y);
}
if (circlePos_ == eBottomLeft) {
qDebug()<<this->parentItem()->boundingRect();
Vec2d ba(a.x()-b.x(), a.y()-b.y());
Vec2d ad(d.x()-a.x(), d.y()-a.y());
Vec2d bd(d.x()-b.x(), d.y()-b.y());
Vec2d bk(pos.x()-b.x(), pos.y()-b.y());
auto ba_len = ba.length();
auto ad_len = ad.length();
auto bd_len = bd.length();
auto bk_len = bk.length();
auto bkbd_dot = Vec2d<qreal>::dot(bd, bk);
auto cos_kdb = bkbd_dot/(bd_len*bk_len);
auto bd2_len = bk_len * cos_kdb;
auto x =(bd2_len * ba_len) / (std::sqrt(ad_len * ad_len + ba_len * ba_len));
auto y = std::sqrt(bd2_len * bd2_len - x * x);
if (x < 10 || y < 10) return;
pos.setX(b.x()-x);
pos.setY(b.y()+y);
}
setPos(pos);
emit circleMoved();
}