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Gwenview: an image viewer
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Copyright 2007 Aurélien Gâteau <agateau@kde.org>
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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#include "imageview.moc"
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#include <QApplication>
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#include <QPaintEvent>
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#include "abstractimageviewtool.h"
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#include "imagescaler.h"
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#define LOG(x) kDebug() << x
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struct ImageViewPrivate {
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QPixmap mBackgroundTexture;
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ImageView::AlphaBackgroundMode mAlphaBackgroundMode;
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QColor mAlphaBackgroundColor;
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bool mEnlargeSmallerImages;
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Document::Ptr mDocument;
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QPixmap mCurrentBuffer;
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QPixmap mAlternateBuffer;
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QPointer<AbstractImageViewTool> mTool;
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QPointer<AbstractImageViewTool> mDefaultTool;
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void createBackgroundTexture() {
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mBackgroundTexture = QPixmap(32, 32);
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QPainter painter(&mBackgroundTexture);
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painter.fillRect(mBackgroundTexture.rect(), QColor(128, 128, 128));
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QColor light = QColor(192, 192, 192);
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painter.fillRect(0, 0, 16, 16, light);
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painter.fillRect(16, 16, 16, 16, light);
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QSize visibleImageSize() const {
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zoom = mView->computeZoomToFit();
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size = mDocument->size() * zoom;
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size = size.boundedTo(mViewport->size());
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void drawAlphaBackground(QPainter* painter, const QRect& viewportRect, const QPoint& zoomedImageTopLeft) {
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if (mAlphaBackgroundMode == ImageView::AlphaBackgroundCheckBoard) {
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zoomedImageTopLeft.x() % mBackgroundTexture.width(),
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zoomedImageTopLeft.y() % mBackgroundTexture.height()
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painter->drawTiledPixmap(
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painter->fillRect(viewportRect, mAlphaBackgroundColor);
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void createBuffer() {
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QSize size = mView->size();
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if (size == mCurrentBuffer.size()) {
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if (!size.isValid()) {
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mAlternateBuffer = QPixmap();
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mCurrentBuffer = QPixmap();
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mAlternateBuffer = QPixmap(size);
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QPainter painter(&mAlternateBuffer);
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QColor bgColor = mViewport->palette().color(mViewport->backgroundRole());
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painter.fillRect(mAlternateBuffer.rect(), bgColor);
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painter.drawPixmap(0, 0, mCurrentBuffer);
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qSwap(mAlternateBuffer, mCurrentBuffer);
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mAlternateBuffer = QPixmap();
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int hScroll() const {
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return mView->horizontalScrollBar()->value();
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int vScroll() const {
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return mView->verticalScrollBar()->value();
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QRect mapViewportToZoomedImage(const QRect& viewportRect) {
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QPoint offset = mView->imageOffset();
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viewportRect.x() + hScroll() - offset.x(),
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viewportRect.y() + vScroll() - offset.y(),
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viewportRect.width(),
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viewportRect.height()
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void setScalerRegionToVisibleRect() {
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QRect rect = mapViewportToZoomedImage(mViewport->rect());
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mScaler->setDestinationRegion(QRegion(rect));
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void forceBufferRecreation() {
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mCurrentBuffer = QPixmap();
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setScalerRegionToVisibleRect();
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void startAnimationIfNecessary() {
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if (mDocument && mView->isVisible()) {
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mDocument->startAnimation();
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// At least gcc 3.4.6 on FreeBSD requires a default constructor.
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ImageViewPrivate() { }
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ImageView::ImageView(QWidget* parent)
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: QAbstractScrollArea(parent)
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, d(new ImageViewPrivate)
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d->mAlphaBackgroundMode = AlphaBackgroundCheckBoard;
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d->mAlphaBackgroundColor = Qt::black;
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d->mZoomToFit = true;
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d->createBackgroundTexture();
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setFrameShape(QFrame::NoFrame);
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setBackgroundRole(QPalette::Base);
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d->mViewport = new QWidget();
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setViewport(d->mViewport);
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d->mViewport->setMouseTracking(true);
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horizontalScrollBar()->setSingleStep(16);
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verticalScrollBar()->setSingleStep(16);
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d->mScaler = new ImageScaler(this);
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d->mInsideSetZoom = false;
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if (QApplication::isRightToLeft()) {
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// Ensure we don't get weird behavior in RightToleft mode
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horizontalScrollBar()->setLayoutDirection(Qt::LeftToRight);
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connect(d->mScaler, SIGNAL(scaledRect(int, int, const QImage&)),
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SLOT(updateFromScaler(int, int, const QImage&)) );
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ImageView::~ImageView() {
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void ImageView::setAlphaBackgroundMode(AlphaBackgroundMode mode) {
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d->mAlphaBackgroundMode = mode;
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if (d->mDocument && d->mDocument->hasAlphaChannel()) {
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d->forceBufferRecreation();
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void ImageView::setAlphaBackgroundColor(const QColor& color) {
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d->mAlphaBackgroundColor = color;
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if (d->mDocument && d->mDocument->hasAlphaChannel()) {
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d->forceBufferRecreation();
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void ImageView::setEnlargeSmallerImages(bool value) {
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d->mEnlargeSmallerImages = value;
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setZoom(computeZoomToFit());
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void ImageView::setDocument(Document::Ptr document) {
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d->mDocument->stopAnimation();
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disconnect(d->mDocument.data(), 0, this, 0);
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d->mDocument = document;
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d->mViewport->update();
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connect(d->mDocument.data(), SIGNAL(metaInfoLoaded(const KUrl&)),
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SLOT(slotDocumentMetaInfoLoaded()) );
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connect(d->mDocument.data(), SIGNAL(isAnimatedUpdated()),
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SLOT(slotDocumentIsAnimatedUpdated()) );
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const Document::LoadingState state = d->mDocument->loadingState();
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if (state == Document::MetaInfoLoaded || state == Document::Loaded) {
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slotDocumentMetaInfoLoaded();
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void ImageView::slotDocumentMetaInfoLoaded() {
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if (d->mDocument->size().isValid()) {
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// Could not retrieve image size from meta info, we need to load the
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connect(d->mDocument.data(), SIGNAL(loaded(const KUrl&)),
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SLOT(finishSetDocument()) );
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d->mDocument->startLoadingFullImage();
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void ImageView::finishSetDocument() {
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if (!d->mDocument->size().isValid()) {
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kError() << "No valid image size available, this should not happen!";
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d->mScaler->setDocument(d->mDocument);
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connect(d->mDocument.data(), SIGNAL(imageRectUpdated(const QRect&)),
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SLOT(updateImageRect(const QRect&)) );
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// Set the zoom to an invalid value to make sure setZoom() does not
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// return early because the new zoom is the same as the old zoom.
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setZoom(computeZoomToFit());
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QRect rect(QPoint(0, 0), d->mDocument->size());
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updateImageRect(rect);
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d->startAnimationIfNecessary();
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d->mViewport->update();
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Document::Ptr ImageView::document() const {
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void ImageView::slotDocumentIsAnimatedUpdated() {
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d->startAnimationIfNecessary();
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void ImageView::updateImageRect(const QRect& imageRect) {
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LOG("imageRect" << imageRect);
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QRect viewportRect = mapToViewport(imageRect);
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viewportRect = viewportRect.intersected(d->mViewport->rect());
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if (viewportRect.isEmpty()) {
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setZoom(computeZoomToFit());
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d->setScalerRegionToVisibleRect();
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d->mViewport->update();
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void ImageView::paintEvent(QPaintEvent* event) {
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QPainter painter(d->mViewport);
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painter.setClipRect(event->rect());
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painter.setCompositionMode(QPainter::CompositionMode_Source);
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painter.drawPixmap(0, 0, d->mCurrentBuffer);
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painter.setCompositionMode(QPainter::CompositionMode_SourceOver);
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d->mTool->paint(&painter);
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void ImageView::resizeEvent(QResizeEvent*) {
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// Bypass "same zoom" test: even if the zoom is the same we want a new
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// buffer of the correct size (and if switching from/to fullscreen, using
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// the correct background) to be created
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setZoom(computeZoomToFit());
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// Make sure one can't use mousewheel in zoom-to-fit mode
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horizontalScrollBar()->setRange(0, 0);
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verticalScrollBar()->setRange(0, 0);
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d->setScalerRegionToVisibleRect();
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QPoint ImageView::imageOffset() const {
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QSize size = d->visibleImageSize();
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int left = qMax( (d->mViewport->width() - size.width()) / 2, 0);
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int top = qMax( (d->mViewport->height() - size.height()) / 2, 0);
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return QPoint(left, top);
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void ImageView::setZoom(qreal zoom, const QPoint& _center) {
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qreal oldZoom = d->mZoom;
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if (qAbs(zoom - oldZoom) < 0.001) {
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// Get offset *before* setting mZoom, otherwise we get the new offset
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QPoint oldOffset = imageOffset();
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if (_center == QPoint(-1, -1)) {
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center = QPoint(d->mViewport->width() / 2, d->mViewport->height() / 2);
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// If we zoom more than twice, then assume the user wants to see the real
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// pixels, for example to fine tune a crop operation
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d->mScaler->setTransformationMode(Qt::SmoothTransformation);
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d->mScaler->setTransformationMode(Qt::FastTransformation);
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d->mInsideSetZoom = true;
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We want to keep the point at viewport coordinates "center" at the same
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position after zooming. The coordinates of this point in image coordinates
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can be expressed like this:
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imagePointAtOldZoom = ------------------
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imagePointAtZoom = ---------------
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imagePointAtOldZoom = imagePointAtZoom
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oldScroll + center scroll + center
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<=> ------------------ = ---------------
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<=> scroll = ------- (oldScroll + center) - center
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It's useless to take the new offset in consideration because if a direction
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of the new offset is not 0, we won't be able to center on a specific point
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QPointF oldScroll = QPointF(d->hScroll(), d->vScroll()) - oldOffset;
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QPointF scroll = (zoom / oldZoom) * (oldScroll + center) - center;
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horizontalScrollBar()->setValue(int(scroll.x()));
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verticalScrollBar()->setValue(int(scroll.y()));
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d->mInsideSetZoom = false;
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d->mScaler->setZoom(d->mZoom);
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d->setScalerRegionToVisibleRect();
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emit zoomChanged(d->mZoom);
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qreal ImageView::zoom() const {
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bool ImageView::zoomToFit() const {
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return d->mZoomToFit;
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void ImageView::setZoomToFit(bool on) {
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setZoom(computeZoomToFit());
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void ImageView::updateScrollBars() {
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if (!d->mDocument || d->mZoomToFit) {
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setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
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setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
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setHorizontalScrollBarPolicy(Qt::ScrollBarAsNeeded);
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setVerticalScrollBarPolicy(Qt::ScrollBarAsNeeded);
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int width = d->mViewport->width();
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int height = d->mViewport->height();
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max = qMax(0, int(d->mDocument->width() * d->mZoom) - width);
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horizontalScrollBar()->setRange(0, max);
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horizontalScrollBar()->setPageStep(width);
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max = qMax(0, int(d->mDocument->height() * d->mZoom) - height);
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verticalScrollBar()->setRange(0, max);
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verticalScrollBar()->setPageStep(height);
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void ImageView::scrollContentsBy(int dx, int dy) {
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if (d->mInsideSetZoom) {
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// Do not scroll anything: since we are zooming the whole viewport will
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// eventually be repainted
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if (d->mAlternateBuffer.size() != d->mCurrentBuffer.size()) {
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d->mAlternateBuffer = QPixmap(d->mCurrentBuffer.size());
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QPainter painter(&d->mAlternateBuffer);
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painter.drawPixmap(dx, dy, d->mCurrentBuffer);
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qSwap(d->mCurrentBuffer, d->mAlternateBuffer);
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// Scale missing parts
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int posX = d->hScroll();
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int posY = d->vScroll();
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int width = d->mViewport->width();
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int height = d->mViewport->height();
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rect = QRect(posX, posY, dx, height);
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rect = QRect(posX + width + dx, posY, -dx, height);
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rect = QRect(posX, posY, width, dy);
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rect = QRect(posX, posY + height + dy, width, -dy);
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d->mScaler->setDestinationRegion(region);
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d->mViewport->update();
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void ImageView::updateFromScaler(int zoomedImageLeft, int zoomedImageTop, const QImage& image) {
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QPoint offset = imageOffset();
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int viewportLeft = offset.x() + zoomedImageLeft - d->hScroll();
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int viewportTop = offset.y() + zoomedImageTop - d->vScroll();
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QPainter painter(&d->mCurrentBuffer);
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if (d->mDocument->hasAlphaChannel()) {
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d->drawAlphaBackground(
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&painter, QRect(viewportLeft, viewportTop, image.width(), image.height()),
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QPoint(zoomedImageLeft, zoomedImageTop)
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painter.setCompositionMode(QPainter::CompositionMode_Source);
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painter.drawImage(viewportLeft, viewportTop, image);
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// Clear borders. We do it here which is quite late, but this way we ensure
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// borders are not cleared until the new image is ready. Meanwhile we
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// continue to show the previous image. If we cleared the borders earlier
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// we could end up clearing the borders on the previous image, leading to
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// a temporary cropped result
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QColor bgColor = d->mViewport->palette().color(d->mViewport->backgroundRole());
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QRegion region = d->mCurrentBuffer.rect();
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region -= QRect(imageOffset(), d->mDocument->size() * d->mZoom);
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Q_FOREACH(const QRect& rect, region.rects()) {
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painter.fillRect(rect, bgColor);
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pen.setStyle(Qt::DotLine);
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painter.drawRect(viewportLeft, viewportTop, image.width() - 1, image.height() - 1);
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d->mViewport->update();
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void ImageView::setCurrentTool(AbstractImageViewTool* tool) {
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d->mTool->toolDeactivated();
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d->mTool = tool ? QPointer<AbstractImageViewTool>(tool) : d->mDefaultTool;
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d->mTool->toolActivated();
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d->mViewport->update();
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AbstractImageViewTool* ImageView::currentTool() const {
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void ImageView::setDefaultTool(AbstractImageViewTool* tool) {
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d->mDefaultTool = tool;
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if (!d->mTool && tool) {
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setCurrentTool(tool);
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AbstractImageViewTool* ImageView::defaultTool() const {
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return d->mDefaultTool;
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QPoint ImageView::mapToViewport(const QPoint& src) const {
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QPoint dst(int(src.x() * d->mZoom), int(src.y() * d->mZoom));
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dst += imageOffset();
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dst.rx() -= d->hScroll();
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dst.ry() -= d->vScroll();
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QPointF ImageView::mapToViewportF(const QPointF& src) const {
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QPointF dst(src.x() * d->mZoom, src.y() * d->mZoom);
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dst += imageOffset();
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dst.rx() -= d->hScroll();
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dst.ry() -= d->vScroll();
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QRect ImageView::mapToViewport(const QRect& src) const {
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mapToViewport(src.topLeft()),
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mapToViewport(src.bottomRight())
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QRectF ImageView::mapToViewportF(const QRectF& src) const {
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mapToViewportF(src.topLeft()),
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mapToViewportF(src.bottomRight())
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QPoint ImageView::mapToImage(const QPoint& src) const {
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dst.rx() += d->hScroll();
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dst.ry() += d->vScroll();
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dst -= imageOffset();
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return QPoint(int(dst.x() / d->mZoom), int(dst.y() / d->mZoom));
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QPointF ImageView::mapToImageF(const QPointF& src) const {
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dst.rx() += d->hScroll();
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dst.ry() += d->vScroll();
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dst -= imageOffset();
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return dst / d->mZoom;
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QRect ImageView::mapToImage(const QRect& src) const {
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mapToImage(src.topLeft()),
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mapToImage(src.bottomRight())
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QRectF ImageView::mapToImageF(const QRectF& src) const {
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mapToImageF(src.topLeft()),
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mapToImageF(src.bottomRight())
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qreal ImageView::computeZoomToFit() const {
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qreal zoom = qMin(computeZoomToFitWidth(), computeZoomToFitHeight());
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if (!d->mEnlargeSmallerImages) {
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zoom = qMin(zoom, qreal(1.0));
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qreal ImageView::computeZoomToFitWidth() const {
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if (!d->mDocument || !d->mDocument->size().isValid()) {
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return qreal(d->mViewport->width()) / d->mDocument->width();
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qreal ImageView::computeZoomToFitHeight() const {
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if (!d->mDocument || !d->mDocument->size().isValid()) {
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return qreal(d->mViewport->height()) / d->mDocument->height();
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void ImageView::showEvent(QShowEvent* event) {
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QAbstractScrollArea::showEvent(event);
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d->startAnimationIfNecessary();
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void ImageView::hideEvent(QHideEvent* event) {
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QAbstractScrollArea::hideEvent(event);
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d->mDocument->stopAnimation();
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void ImageView::mousePressEvent(QMouseEvent* event) {
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d->mTool->mousePressEvent(event);
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void ImageView::mouseMoveEvent(QMouseEvent* event) {
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d->mTool->mouseMoveEvent(event);
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void ImageView::mouseReleaseEvent(QMouseEvent* event) {
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d->mTool->mouseReleaseEvent(event);
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void ImageView::wheelEvent(QWheelEvent* event) {
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d->mTool->wheelEvent(event);
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void ImageView::keyPressEvent(QKeyEvent* event) {
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d->mTool->keyPressEvent(event);
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QAbstractScrollArea::keyPressEvent(event);
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void ImageView::keyReleaseEvent(QKeyEvent* event) {
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d->mTool->keyReleaseEvent(event);
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QAbstractScrollArea::keyReleaseEvent(event);
added
removed
lib/imageview.cpp
