// really generate the cache
void ImageView::generateCache() {
// disable the one-shot timer
cacheTimer_->deleteLater();
cacheTimer_ = nullptr;
if(!imageItem_ || image_.isNull()) return;
// generate a cache for "the visible part" of the scaled image
// rectangle of the whole image in viewport coordinate
QRect viewportImageRect = sceneToViewport(imageItem_->rect());
// rect of the image area that's visible in the viewport (in viewport coordinate)
cachedRect_ = viewportImageRect.intersected(viewport()->rect());
// convert to the coordinate of the original image
cachedSceneRect_ = viewportToScene(cachedRect_);
// create a sub image of the visible without real data copy
// Reference: http://stackoverflow.com/questions/12681554/dividing-qimage-to-smaller-pieces
QRect subRect = image_.rect().intersected(cachedSceneRect_);
const uchar* bits = image_.constBits();
unsigned int offset = subRect.x() * image_.depth() / 8 + subRect.y() * image_.bytesPerLine();
QImage subImage = QImage(bits + offset, subRect.width(), subRect.height(), image_.bytesPerLine(), image_.format());
// If the original image has a color table, also use it for the subImage
QVector<QRgb> colorTable = image_.colorTable();
if (!colorTable.empty())
subImage.setColorTable(colorTable);
// QImage scaled = subImage.scaled(subRect.width() * scaleFactor_, subRect.height() * scaleFactor_, Qt::KeepAspectRatio, Qt::SmoothTransformation);
QImage scaled = subImage.scaled(cachedRect_.width(), cachedRect_.height(), Qt::KeepAspectRatio, Qt::SmoothTransformation);
// convert the cached scaled image to pixmap
cachedPixmap_ = QPixmap::fromImage(scaled);
viewport()->update();
}
void ImageView::paintEvent(QPaintEvent* event) {
// if the image is scaled and we have a high quality cached image
if(imageItem_ && scaleFactor_ != 1.0 && !cachedPixmap_.isNull()) {
// rectangle of the whole image in viewport coordinate
QRect viewportImageRect = sceneToViewport(imageItem_->rect());
// the visible part of the image.
QRect desiredCachedRect = viewportToScene(viewportImageRect.intersected(viewport()->rect()));
// check if the cached area is what we need and if the cache is out of date
if(cachedSceneRect_ == desiredCachedRect) {
// rect of the image area that needs repaint, in viewport coordinate
QRect repaintImageRect = viewportImageRect.intersected(event->rect());
// see if the part asking for repaint is contained by our cache.
if(cachedRect_.contains(repaintImageRect)) {
QPainter painter(viewport());
painter.fillRect(event->rect(), backgroundBrush());
painter.drawPixmap(repaintImageRect, cachedPixmap_);
return;
}
}
}
if(!image_.isNull()) { // we don't have a cache yet or it's out of date already, generate one
queueGenerateCache();
}
QGraphicsView::paintEvent(event);
}
void ImageView::generateCache()
{
delete m_cacheTimer;
m_cacheTimer = 0;
if (!m_item)
return;
m_cachedRect = sceneToViewport(m_item->rect()).intersected(viewport()->rect());
m_cachedSceneRect = viewportToScene(m_cachedRect);
const QRect subRect = m_image.rect().intersected(m_cachedSceneRect);
# if QT_VERSION >= 0x040700
const uchar* bits = m_image.constBits();
# else
const uchar* bits = m_image.bits();
# endif
const unsigned int offset = subRect.x() * m_image.depth() / 8 + subRect.y() * m_image.bytesPerLine();
const QImage subImage = QImage(bits + offset, subRect.width(), subRect.height(), m_image.bytesPerLine(), m_image.format());
ScaleRunnable *runnable = new ScaleRunnable(subImage.copy(), m_cachedRect.size());
connect(runnable, SIGNAL(finished(QImage)), SLOT(onFinished(QImage)));
QThreadPool::globalInstance()->start(runnable);
}
Rect2 Graphic::Renderer::viewportToScene(Rect2 const& rect) const {
if (_scene == NULL)
throw new Graphic::Exception("Tried to transform coords but no scene was specified");
Vec2 viewport = getViewportSize();
Vec2 scene = _scene->getViewport();
Vec2 newPos = viewportToScene(rect.pos);
Vec2 newSize = rect.size / viewport * scene;
newPos.y -= newSize.y;
Rect2 newRect(newPos, Vec2(newSize));
return newRect;
}
void ImageView::paintEvent(QPaintEvent* event)
{
if (m_item && m_scaleFactor != 1.0 && !m_cachedPixmap.isNull()) {
const QRect viewportImageRect = sceneToViewport(m_item->rect());
const QRect desiredCachedRect = viewportToScene(viewportImageRect.intersected(viewport()->rect()));
if (m_cachedSceneRect == desiredCachedRect) {
const QRect repaintImageRect = viewportImageRect.intersected(event->rect());
if (m_cachedRect.contains(repaintImageRect)) {
QPainter painter(viewport());
painter.fillRect(event->rect(), backgroundBrush());
painter.drawPixmap(repaintImageRect, m_cachedPixmap);
return;
}
}
}
if (!m_image.isNull())
queueGenerateCache();
QGraphicsView::paintEvent(event);
}
