Plug & Paint Example

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#include "interfaces.h" #include "paintarea.h" #include <QMouseEvent> #include <QPainter> PaintArea::PaintArea(QWidget *parent) : QWidget(parent) { setAttribute(Qt::WA_StaticContents); setAttribute(Qt::WA_NoBackground); theImage.fill(qRgb(255, 255, 255)); } bool PaintArea::openImage(const QString &fileName) { QImage image; if (!image.load(fileName)) return false; setImage(image); return true; } bool PaintArea::saveImage(const QString &fileName, const char *fileFormat) { return theImage.save(fileName, fileFormat); } void PaintArea::setImage(const QImage &image) { theImage = image.convertToFormat(QImage::Format_RGB32); update(); updateGeometry(); } void PaintArea::insertShape(const QPainterPath &path) { pendingPath = path; #ifndef QT_NO_CURSOR setCursor(Qt::CrossCursor); #endif } void PaintArea::setBrushColor(const QColor &color) { this->color = color; } void PaintArea::setBrushWidth(int width) { thickness = width; } void PaintArea::setBrush(BrushInterface *brushInterface, const QString &brush) { this->brushInterface = brushInterface; this->brush = brush; } QSize PaintArea::sizeHint() const { return theImage.size(); } void PaintArea::paintEvent(QPaintEvent * /* event */) { QPainter painter(this); painter.drawImage(QPoint(0, 0), theImage); } void PaintArea::mousePressEvent(QMouseEvent *event) { if (event->button() == Qt::LeftButton) { if (!pendingPath.isEmpty()) { QPainter painter(&theImage); setupPainter(painter); const QRectF boundingRect = pendingPath.boundingRect(); QLinearGradient gradient(boundingRect.topRight(), boundingRect.bottomLeft()); gradient.setColorAt(0.0, QColor(color.red(), color.green(), color.blue(), 63)); gradient.setColorAt(1.0, QColor(color.red(), color.green(), color.blue(), 191)); painter.setBrush(gradient); painter.translate(event->pos() - boundingRect.center()); painter.drawPath(pendingPath); pendingPath = QPainterPath(); #ifndef QT_NO_CURSOR unsetCursor(); #endif update(); } else { if (brushInterface) { QPainter painter(&theImage); setupPainter(painter); const QRect rect = brushInterface->mousePress(brush, painter, event->pos()); update(rect); } lastPos = event->pos(); } } } void PaintArea::mouseMoveEvent(QMouseEvent *event) { if ((event->buttons() & Qt::LeftButton) && lastPos != QPoint(-1, -1)) { if (brushInterface) { QPainter painter(&theImage); setupPainter(painter); const QRect rect = brushInterface->mouseMove(brush, painter, lastPos, event->pos()); update(rect); } lastPos = event->pos(); } } void PaintArea::mouseReleaseEvent(QMouseEvent *event) { if (event->button() == Qt::LeftButton && lastPos != QPoint(-1, -1)) { if (brushInterface) { QPainter painter(&theImage); setupPainter(painter); QRect rect = brushInterface->mouseRelease(brush, painter, event->pos()); update(rect); } lastPos = QPoint(-1, -1); } } void PaintArea::setupPainter(QPainter &painter) { painter.setRenderHint(QPainter::Antialiasing, true); painter.setPen(QPen(color, thickness, Qt::SolidLine, Qt::RoundCap, Qt::RoundJoin)); }