QImage vs QImageReader
QImage is not good choice for scaling images (like QImage::load() + QImage::scaled()).
QImageReader API is better approach than loading full image into memory and stretching it there. QImageReader API allows to set needed scaling limitations first and then load it. The image will be scaled as part of loading process and there is no needs to allocate memory for full size image.
pattern: QImageReader::setScaledSize() + QImageReader::read()
