如果你想使用eraseRect()
函数来实现橡皮擦功能,可以通过以下方式修改示例代码:
#include <QApplication>
#include <QWidget>
#include <QPainter>
#include <QMouseEvent>
class Whiteboard : public QWidget
{
public:
Whiteboard(QWidget* parent = nullptr)
: QWidget(parent), m_eraserSize(10), m_drawing(false)
{
setAttribute(Qt::WA_StaticContents);
}
protected:
void mousePressEvent(QMouseEvent* event) override
{
if (event->button() == Qt::LeftButton) {
m_lastPos = event->pos();
m_drawing = true;
}
}
void mouseMoveEvent(QMouseEvent* event) override
{
if ((event->buttons() & Qt::LeftButton) && m_drawing) {
QPainter painter(&m_image);
painter.setCompositionMode(QPainter::CompositionMode_Clear); // 使用透明绘制模式
painter.eraseRect(event->x() - m_eraserSize/2, event->y() - m_eraserSize/2,
m_eraserSize, m_eraserSize);
update();
}
}
void mouseReleaseEvent(QMouseEvent* event) override
{
if (event->button() == Qt::LeftButton && m_drawing) {
QPainter painter(&m_image);
painter.setCompositionMode(QPainter::CompositionMode_Clear); // 使用透明绘制模式
painter.eraseRect(event->x() - m_eraserSize/2, event->y() - m_eraserSize/2,
m_eraserSize, m_eraserSize);
update();
// 擦除完成后保存绘制结果
saveImage();
m_drawing = false;
}
}
void paintEvent(QPaintEvent* event) override
{
QPainter painter(this);
QRect dirtyRect = event->rect();
painter.drawImage(dirtyRect, m_image, dirtyRect);
}
void resizeEvent(QResizeEvent* event) override
{
if (width() > m_image.width() || height() > m_image.height()) {
int newWidth = qMax(width() + 128, m_image.width());
int newHeight = qMax(height() + 128, m_image.height());
resizeImage(&m_image, QSize(newWidth, newHeight));
update();
}
QWidget::resizeEvent(event);
}
private:
void resizeImage(QImage* image, const QSize& newSize)
{
if (image->size() == newSize)
return;
QImage newImage(newSize, QImage::Format_ARGB32_Premultiplied);
newImage.fill(Qt::transparent);
QPainter painter(&newImage);
painter.drawImage(QPoint(0, 0), *image);
*image = newImage;
}
void saveImage()
{
// 在这里实现保存擦除后的绘图结果
// 可以将图片保存到文件或者进行其他操作
// 示例中暂未给出具体实现方法,可以根据需求自行扩展
}
private:
QImage m_image;
int m_eraserSize;
bool m_drawing;
QPoint m_lastPos;
};
int main(int argc, char** argv)
{
QApplication app(argc, argv);
Whiteboard whiteboard;
whiteboard.resize(800, 600);
whiteboard.show();
return app.exec();
}
在修改后的代码中,我们使用QPainter::CompositionMode_Clear
绘制模式,并且使用eraseRect()
函数在鼠标移动和释放事件中来擦除矩形区域。这样就可以实现橡皮擦的功能了。记得根据需要来保存擦除后的绘图结果,在示例中的saveImage函数中进行相应的操作。
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