Mandelbrot Example

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#include "mandelbrotwidget.h" #include <QPainter> #include <QKeyEvent> #include <math.h> const double DefaultCenterX = -0.637011f; const double DefaultCenterY = -0.0395159f; const double DefaultScale = 0.00403897f; const double ZoomInFactor = 0.8f; const double ZoomOutFactor = 1 / ZoomInFactor; const int ScrollStep = 20; MandelbrotWidget::MandelbrotWidget(QWidget *parent) : QWidget(parent) { centerX = DefaultCenterX; centerY = DefaultCenterY; pixmapScale = DefaultScale; curScale = DefaultScale; connect(&thread, &RenderThread::renderedImage, this, &MandelbrotWidget::updatePixmap); setWindowTitle(tr("Mandelbrot")); #ifndef QT_NO_CURSOR setCursor(Qt::CrossCursor); #endif resize(550, 400); } void MandelbrotWidget::paintEvent(QPaintEvent * /* event */) { QPainter painter(this); painter.fillRect(rect(), Qt::black); if (pixmap.isNull()) { painter.setPen(Qt::white); painter.drawText(rect(), Qt::AlignCenter, tr("Rendering initial image, please wait...")); return; } if (curScale == pixmapScale) { painter.drawPixmap(pixmapOffset, pixmap); } else { double scaleFactor = pixmapScale / curScale; int newWidth = int(pixmap.width() * scaleFactor); int newHeight = int(pixmap.height() * scaleFactor); int newX = pixmapOffset.x() + (pixmap.width() - newWidth) / 2; int newY = pixmapOffset.y() + (pixmap.height() - newHeight) / 2; painter.save(); painter.translate(newX, newY); painter.scale(scaleFactor, scaleFactor); QRectF exposed = painter.transform().inverted().mapRect(rect()).adjusted(-1, -1, 1, 1); painter.drawPixmap(exposed, pixmap, exposed); painter.restore(); } QString text = tr("Use mouse wheel or the '+' and '-' keys to zoom. " "Press and hold left mouse button to scroll."); QFontMetrics metrics = painter.fontMetrics(); int textWidth = metrics.horizontalAdvance(text); painter.setPen(Qt::NoPen); painter.setBrush(QColor(0, 0, 0, 127)); painter.drawRect((width() - textWidth) / 2 - 5, 0, textWidth + 10, metrics.lineSpacing() + 5); painter.setPen(Qt::white); painter.drawText((width() - textWidth) / 2, metrics.leading() + metrics.ascent(), text); } void MandelbrotWidget::resizeEvent(QResizeEvent * /* event */) { thread.render(centerX, centerY, curScale, size()); } void MandelbrotWidget::keyPressEvent(QKeyEvent *event) { switch (event->key()) { case Qt::Key_Plus: zoom(ZoomInFactor); break; case Qt::Key_Minus: zoom(ZoomOutFactor); break; case Qt::Key_Left: scroll(-ScrollStep, 0); break; case Qt::Key_Right: scroll(+ScrollStep, 0); break; case Qt::Key_Down: scroll(0, -ScrollStep); break; case Qt::Key_Up: scroll(0, +ScrollStep); break; default: QWidget::keyPressEvent(event); } } #if QT_CONFIG(wheelevent) void MandelbrotWidget::wheelEvent(QWheelEvent *event) { int numDegrees = event->delta() / 8; double numSteps = numDegrees / 15.0f; zoom(pow(ZoomInFactor, numSteps)); } #endif void MandelbrotWidget::mousePressEvent(QMouseEvent *event) { if (event->button() == Qt::LeftButton) lastDragPos = event->pos(); } void MandelbrotWidget::mouseMoveEvent(QMouseEvent *event) { if (event->buttons() & Qt::LeftButton) { pixmapOffset += event->pos() - lastDragPos; lastDragPos = event->pos(); update(); } } void MandelbrotWidget::mouseReleaseEvent(QMouseEvent *event) { if (event->button() == Qt::LeftButton) { pixmapOffset += event->pos() - lastDragPos; lastDragPos = QPoint(); int deltaX = (width() - pixmap.width()) / 2 - pixmapOffset.x(); int deltaY = (height() - pixmap.height()) / 2 - pixmapOffset.y(); scroll(deltaX, deltaY); } } void MandelbrotWidget::updatePixmap(const QImage &image, double scaleFactor) { if (!lastDragPos.isNull()) return; pixmap = QPixmap::fromImage(image); pixmapOffset = QPoint(); lastDragPos = QPoint(); pixmapScale = scaleFactor; update(); } void MandelbrotWidget::zoom(double zoomFactor) { curScale *= zoomFactor; update(); thread.render(centerX, centerY, curScale, size()); } void MandelbrotWidget::scroll(int deltaX, int deltaY) { centerX += deltaX * curScale; centerY += deltaY * curScale; update(); thread.render(centerX, centerY, curScale, size()); }