How to animate/change color of QPixmap/QImage/QPicture/whatever on mouseEvents?

[deleted385]

What I basically want is a button, with svg icon / path data, and without any text which will change color (animate) on enter, leave, press. Previously I tried with QAction, doesn't work, and here I've tried another approach with QWidget:

ActionButton::ActionButton(const QString &fileName, QWidget *parent) :QWidget(parent){
    icon = QImage(fileName); // fileName.svg
    auto label = new QLabel();
    label->setPixmap(QPixmap::fromImage(icon));
    auto lay = new QVBoxLayout(this);
    lay->setContentsMargins(0,0,0,0);
    lay->addWidget(label);
    setLayout(lay);
}
void ActionButton::enterEvent(QEnterEvent *event){
    qDebug() << "entered";
    icon.fill(Qt::blue);
}
void ActionButton::leaveEvent(QEvent *event){
    qDebug() << "left";
    icon.fill(Qt::black);
}
void ActionButton::mousePressEvent(QMouseEvent *event){
    qDebug() << "pressed";
    icon.fill(Qt::red);
}

it detects correctly the enter, leave and press BUT doesn't change color. It also doesn't resize the image when I reset label width and height.

EDIT
Like this:

[eyllanesc]

@eyllanesc You have to modify the svg attributes for example using QtXml

#include <QApplication>
#include <QDomDocument>
#include <QEnterEvent>
#include <QFile>
#include <QLabel>
#include <QPainter>
#include <QSvgRenderer>
#include <QVBoxLayout>
#include <QWidget>

#include <QDebug>

class ActionButton: public QWidget{
public:
    ActionButton(const QString & filename, QWidget *parent=nullptr)
        :QWidget(parent), m_label(new QLabel)
    {
        m_label->setAlignment(Qt::AlignCenter);
        QVBoxLayout *lay = new QVBoxLayout(this);
        lay->addWidget(m_label);
        QFile f(filename);
        if(f.open(QIODevice::ReadOnly | QIODevice::Text)){
            m_document.setContent(f.readAll());
        }
        changeColor(QColor("red"));
    }
protected:
    void enterEvent(QEvent *event)
    {
        QWidget::enterEvent(event);
        qDebug() << "entered";
        changeColor(Qt::blue);
    }
    void leaveEvent(QEvent *event){
        QWidget::leaveEvent(event);
        qDebug() << "left";
        changeColor(Qt::black);
    }
    void mousePressEvent(QMouseEvent *event){
        QWidget::mousePressEvent(event);
        qDebug() << "pressed";
        changeColor(Qt::red);
    }
private:
    void changeColor(const QColor & color){
        QDomNodeList  path_elements = m_document.elementsByTagName("path");
        if(path_elements.length() > 0){
            QDomNode path_node = path_elements.at(0);
            if(path_node.isElement()){
                QDomElement path_element = path_node.toElement();
                path_element.setAttribute("fill", color.name());
            }
        }
        m_renderer.load(m_document.toByteArray());
        QPixmap pixmap(m_renderer.defaultSize());
        pixmap.fill(Qt::transparent);
        QPainter painter(&pixmap);
        m_renderer.render(&painter);
        painter.end();
        m_label->setPixmap(pixmap);
    }
    QSvgRenderer m_renderer;
    QDomDocument m_document;
    QLabel *m_label;
};

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QString filename{"/path/of/database-plus.svg"};
    ActionButton button(filename);
    button.show();
    return a.exec();
}

[eyllanesc]

@Emon-Haque share the .svg

[deleted385]

@eyllanesc, I use this site for path data/svg icons. Right click on any icon, click Download .SVG Compressed on the context menu, you'll get the svg file that works fine in Qt.

[JKSH]

@Emon-Haque said in How to animate/change color of QPixmap/QImage/QPicture/whatever on mouseEvents?:

doesn't resize the image when I reset label width and height

QImage and QPixmap are fixed size. You can update the size by calling QImage::scaled() or QPixmap::scaled(), but you will get pixellation.

If you want resizable SVG, use QSvgWidget instead. Update the size by calling QSvgWidget::resize() -- the SVG will be rendered at the new size without pixellation.

doesn't change color

2 important notes:

• Your code only updates icon. You also need to update label -- these are 2 separate copies of your image.
• QImage::fill() fills the entire image with a solid colour. It doesn't change the colour of an existing image.

Unfortunately, there is no straightforward way to animate colours in a QLabel or QSvgWidget. The alternatives are:

• Put your icon in a QGraphicsView and apply a QGraphicsColorizeEffect (see https://doc.qt.io/qt-5/qgraphicseffect.html )
• Implement your GUI in QML and apply a Colorize effect (see https://doc.qt.io/qt-5/qml-qtgraphicaleffects-colorize.html )

[eyllanesc]

@eyllanesc You have to modify the svg attributes for example using QtXml

#include <QApplication>
#include <QDomDocument>
#include <QEnterEvent>
#include <QFile>
#include <QLabel>
#include <QPainter>
#include <QSvgRenderer>
#include <QVBoxLayout>
#include <QWidget>

#include <QDebug>

class ActionButton: public QWidget{
public:
    ActionButton(const QString & filename, QWidget *parent=nullptr)
        :QWidget(parent), m_label(new QLabel)
    {
        m_label->setAlignment(Qt::AlignCenter);
        QVBoxLayout *lay = new QVBoxLayout(this);
        lay->addWidget(m_label);
        QFile f(filename);
        if(f.open(QIODevice::ReadOnly | QIODevice::Text)){
            m_document.setContent(f.readAll());
        }
        changeColor(QColor("red"));
    }
protected:
    void enterEvent(QEvent *event)
    {
        QWidget::enterEvent(event);
        qDebug() << "entered";
        changeColor(Qt::blue);
    }
    void leaveEvent(QEvent *event){
        QWidget::leaveEvent(event);
        qDebug() << "left";
        changeColor(Qt::black);
    }
    void mousePressEvent(QMouseEvent *event){
        QWidget::mousePressEvent(event);
        qDebug() << "pressed";
        changeColor(Qt::red);
    }
private:
    void changeColor(const QColor & color){
        QDomNodeList  path_elements = m_document.elementsByTagName("path");
        if(path_elements.length() > 0){
            QDomNode path_node = path_elements.at(0);
            if(path_node.isElement()){
                QDomElement path_element = path_node.toElement();
                path_element.setAttribute("fill", color.name());
            }
        }
        m_renderer.load(m_document.toByteArray());
        QPixmap pixmap(m_renderer.defaultSize());
        pixmap.fill(Qt::transparent);
        QPainter painter(&pixmap);
        m_renderer.render(&painter);
        painter.end();
        m_label->setPixmap(pixmap);
    }
    QSvgRenderer m_renderer;
    QDomDocument m_document;
    QLabel *m_label;
};

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QString filename{"/path/of/database-plus.svg"};
    ActionButton button(filename);
    button.show();
    return a.exec();
}

[deleted385]

@JKSH, I've QT += core gui svg in .pro. When I add #include <QSvgWidget> in .h file I get QSvgWidget file not found. How to fix that?

[eyllanesc]

@Emon-Haque what is your Qt version?

[deleted385]

@eyllanesc, 6.2.0

[eyllanesc]

@Emon-Haque Please read the docs: https://doc.qt.io/qt-6/qsvgwidget.html, add

QT += svgwidgets

[deleted385]

@eyllanesc, hmm not bad:

would be nicer if there's some easy way to add a QPropertyAnimation for color. Instead of svg file there should be some way to use path data, to avoid DOM traversing, directly and animate its color.