canvas.cpp
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#include "canvas.h"
#include <QMouseEvent>
#include <QPainter>
Canvas::Canvas(QWidget *parent) : QWidget(parent)
{
setAttribute(Qt::WA_StaticContents);
scribbling = false;
myPenWidth = 1;
myPenColor = Qt::blue;
}
void Canvas::clearImage()
{
image.fill(qRgb(255, 255, 255));
update();
}
void Canvas::mousePressEvent(QMouseEvent *event)
{
if (event->button() == Qt::LeftButton) {
lastPoint = event->pos();
scribbling = true;
}
}
void Canvas::mouseMoveEvent(QMouseEvent *event)
{
if ((event->buttons() & Qt::LeftButton) && scribbling)
drawLineTo(event->pos());
}
void Canvas::mouseReleaseEvent(QMouseEvent *event)
{
if (event->button() == Qt::LeftButton && scribbling) {
drawLineTo(event->pos());
scribbling = false;
}
}
void Canvas::paintEvent(QPaintEvent *event)
{
QPainter painter(this);
QRect dirtyRect = event->rect();
painter.drawImage(dirtyRect, image, dirtyRect);
}
void Canvas::resizeEvent(QResizeEvent *event)
{
if (width() > image.width() || height() > image.height()) {
int newWidth = qMax(width() + 128, image.width());
int newHeight = qMax(height() + 128, image.height());
resizeImage(&image, QSize(newWidth, newHeight));
update();
}
QWidget::resizeEvent(event);
}
void Canvas::drawLineTo(const QPoint &endPoint)
{
QPainter painter(&image);
painter.setPen(QPen(myPenColor, myPenWidth, Qt::SolidLine, Qt::RoundCap,
Qt::RoundJoin));
painter.drawLine(lastPoint, endPoint);
int rad = (myPenWidth / 2) + 2;
update(QRect(lastPoint, endPoint).normalized()
.adjusted(-rad, -rad, +rad, +rad));
lastPoint = endPoint;
}
void Canvas::resizeImage(QImage *image, const QSize &newSize)
{
if (image->size() == newSize)
return;
QImage newImage(newSize, QImage::Format_RGB32);
newImage.fill(qRgb(255, 255, 255));
QPainter painter(&newImage);
painter.drawImage(QPoint(0, 0), *image);
*image = newImage;
}