Consider the scale ratio when scaling down images

fixes #393

src/Utils.cpp

@@ -223,11 +223,41 @@ utils::scaleImageToPixmap(const QImage &img, int size)
  return QPixmap();
 
  const double sz =
- ceil(QApplication::desktop()->screen()->devicePixelRatioF() * (double)size);
+ std::ceil(QApplication::desktop()->screen()->devicePixelRatioF() * (double)size);
  return QPixmap::fromImage(
  img.scaled(sz, sz, Qt::IgnoreAspectRatio, Qt::SmoothTransformation));
 }
 
+QPixmap
+utils::scaleDown(uint64_t maxWidth, uint64_t maxHeight, const QPixmap &source)
+{
+ if (source.isNull())
+ return QPixmap();
+
+ const double pixelRatio = QApplication::desktop()->screen()->devicePixelRatioF();
+
+ // Take into account the scale factor of the screen.
+ maxWidth = std::ceil(pixelRatio * (double)maxWidth);
+ maxHeight = std::ceil(pixelRatio * (double)maxHeight);
+
+ const double widthRatio = (double)maxWidth / (double)source.width();
+ const double heightRatio = (double)maxHeight / (double)source.height();
+ const double minAspectRatio = std::min(widthRatio, heightRatio);
+
+ // Size of the output image.
+ int w, h = 0;
+
+ if (minAspectRatio > 1) {
+ w = source.width();
+ h = source.height();
+ } else {
+ w = source.width() * minAspectRatio;
+ h = source.height() * minAspectRatio;
+ }
+
+ return source.scaled(w, h, Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
+}
+
 QString
 utils::mxcToHttp(const QUrl &url, const QString &server, int port)
 {

src/Utils.h

@@ -116,32 +116,8 @@ createDescriptionInfo(const Event &event, const QString &localUser, const QStrin
 }
 
 //! Scale down an image to fit to the given width & height limitations.
-template<class ImageType>
-ImageType
-scaleDown(uint64_t max_width, uint64_t max_height, const ImageType &source)
-{
- if (source.isNull())
- return QPixmap();
-
- auto width_ratio = (double)max_width / (double)source.width();
- auto height_ratio = (double)max_height / (double)source.height();
-
- auto min_aspect_ratio = std::min(width_ratio, height_ratio);
-
- int final_width = 0;
- int final_height = 0;
-
- if (min_aspect_ratio > 1) {
- final_width = source.width();
- final_height = source.height();
- } else {
- final_width = source.width() * min_aspect_ratio;
- final_height = source.height() * min_aspect_ratio;
- }
-
- return source.scaled(
- final_width, final_height, Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
-}
+QPixmap
+scaleDown(uint64_t maxWidth, uint64_t maxHeight, const QPixmap &source);
 
 //! Delete items in a container based on a predicate.
 template<typename ContainerT, typename PredicateT>

src/dialogs/ImageOverlay.cpp

@@ -68,7 +68,7 @@ ImageOverlay::paintEvent(QPaintEvent *event)
  int max_width = screen_.width() - 2 * outer_margin;
  int max_height = screen_.height();
 
- image_ = utils::scaleDown<QPixmap>(max_width, max_height, originalImage_);
+ image_ = utils::scaleDown(max_width, max_height, originalImage_);
 
  int diff_x = max_width - image_.width();
  int diff_y = max_height - image_.height();

src/dialogs/PreviewUploadOverlay.cpp

@@ -108,7 +108,7 @@ PreviewUploadOverlay::init()
  const auto maxHeight = winsize.height() * 0.8;
 
  // Scale image preview to fit into the application window.
- infoLabel_.setPixmap(utils::scaleDown<QPixmap>(maxWidth, maxHeight, image_));
+ infoLabel_.setPixmap(utils::scaleDown(maxWidth, maxHeight, image_));
  move(center.x() - (width() * 0.5), center.y() - (height() * 0.5));
  } else {
  infoLabel_.setAlignment(Qt::AlignLeft);

src/timeline/widgets/ImageItem.cpp

@@ -126,7 +126,7 @@ void
 ImageItem::setImage(const QPixmap &image)
 {
  image_ = image;
- scaled_image_ = utils::scaleDown<QPixmap>(max_width_, max_height_, image_);
+ scaled_image_ = utils::scaleDown(max_width_, max_height_, image_);
 
  width_ = scaled_image_.width();
  height_ = scaled_image_.height();
@@ -165,7 +165,7 @@ ImageItem::resizeEvent(QResizeEvent *event)
  if (!image_)
  return QWidget::resizeEvent(event);
 
- scaled_image_ = utils::scaleDown<QPixmap>(max_width_, max_height_, image_);
+ scaled_image_ = utils::scaleDown(max_width_, max_height_, image_);
 
  width_ = scaled_image_.width();
  height_ = scaled_image_.height();