Dive pictures: save thumbnails to individual files

The old code loaded all thumbnails into memory at once. This does
not scale to logs with thousands of pictures. Therefore, save
the pictures to individual files and only load the currently
needed pictures.

Currently, this will make changing switching between dives slower,
because the thumbnails are loaded from disk. In the future, it
is planned to do this in a background thread without blocking
the user interface.

A notable difference to the old code: Thumbnails are now indexed
by the image-hash (i.e. the content of the raw image) and not
by the filename of the image. Thus, different paths to the same
image should only be saved once.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

1 files changed, 1 insertions, 0 deletions

diff --git a/core/qthelper.h b/core/qthelper.h
index 4c0dcda66..ac1de4df8 100644
--- a/core/qthelper.h
+++ b/core/qthelper.h
@@ -30,6 +30,7 @@ void write_hashes();
 void updateHash(struct picture *picture);
 QByteArray hashFile(const QString &filename);
 QString hashString(const char *filename);
+QString thumbnailFileName(const QString &filename);
 void learnImages(const QDir dir, int max_recursions);
 void add_hash(const QString &filename, const QByteArray &hash);
 void hashPicture(struct picture *picture);