QImage Exiv2Lib::getPreview()
{
PreviewManager loader(*mImageFile);
PreviewPropertiesList list = loader.getPreviewProperties();
if (list.empty())
{
qDebug() << "Image contains no thumbnail";
return QImage();
}
PreviewProperties selected;
// Take the last image in the list.
// For Canon raw pictures, the 2nd preview has no white balance applied.
// see http://lclevy.free.fr/cr2/
// section 2.6 IFD #2
selected = list.back();
// FIXME: crash hapened here when reading the QImage.
// not quite sure what caused it
// load the thumbnail
PreviewImage thumbnail = loader.getPreviewImage(selected);
const unsigned char* tmp = thumbnail.pData();
size_t size = thumbnail.size();
QImage thumb;
thumb.loadFromData(tmp, size);
// Read the EXIF orientation flag and rotate the image accordingly.
ExifData& data = mImageFile->exifData();
ExifData::const_iterator pos;
pos = data.findKey(ExifKey("Exif.Image.Orientation"));
// TODO: should flip/rotate after resize
if (pos != data.end())
{
qDebug() << "rotation" << pos->toLong();
QTransform rotate;
switch (pos->toLong())
{
case 1: // no rotation needed
break;
case 2: // flip over y
thumb = thumb.mirrored(true, false);
break;
case 3: // rotate 180 (or flip x flip y)
thumb = thumb.mirrored(true, true);
break;
case 4: // flip over x
thumb = thumb.mirrored(false, true);
break;
case 5: // rotate 90 CW & flip over y
rotate.rotate(90);
rotate.rotate(180, Qt::YAxis);
thumb = thumb.transformed(rotate);
break;
case 6: // rotate 90 CW
rotate.rotate(90);
thumb = thumb.transformed(rotate);
break;
case 7: // rotate 90 CCW flip over y
rotate.rotate(-90);
rotate.rotate(180, Qt::YAxis);
thumb = thumb.transformed(rotate);
break;
case 8: // rotate 90 CCW
rotate.rotate(-90);
thumb = thumb.transformed(rotate);
break;
}
}
return thumb;
}
