[digikam] utilities/mediaserver: Huge improvement of Media Server here : Serve all image formats supported by digiKam core engine.

[Gilles Caulier]

Git commit 7319025b6a448ec367c66dc44dc22cbfe0b75289 by Gilles Caulier.
Committed on 29/09/2017 at 11:59.
Pushed by cgilles into branch 'master'.

Huge improvement of Media Server here : Serve all image formats supported by digiKam core engine.

The image is not passed as well as an bytes stream as file is read and push on web server, delegating the
mime type analysis and decoding to the renderer.

The idea here is to transcoding the image by extracting the reduced image preview and share it as JPEG.

This will prevent to bloat the network with huge data, reduce time latency with huge image (as panorama),
and prevent crash in client renderer application in case of reduced memory available to host full image data.

By this way we can serve all image formats supported by digiKam, including all RAW file formats.
As i know there is no Upnp/DLNA media server able to share RAW files on the network with this kind of transparency.

In case of non image format to serve, the file is shared as well, as previously. There is no transcoding.

TODO: We need to do something similar with video files, as to transcoding media with a low band of data on the network.
The question is : ffmpeg is able to do it in background (as Kodi do in delegate implementation), but QtAV is able to do it
with current API without to pass directly to ffmpeg ?

CCMAIL: digikam-devel at kde.org

M  +99   -2    utilities/mediaserver/dlnaserverdelegate.cpp

https://commits.kde.org/digikam/7319025b6a448ec367c66dc44dc22cbfe0b75289

diff --git a/utilities/mediaserver/dlnaserverdelegate.cpp b/utilities/mediaserver/dlnaserverdelegate.cpp
index fdfcdaafa1..4730b9f653 100644
--- a/utilities/mediaserver/dlnaserverdelegate.cpp
+++ b/utilities/mediaserver/dlnaserverdelegate.cpp
@@ -25,6 +25,8 @@
 
 // Platinum includes
 
+#include "NptStreams.h"
+
 #include "PltUPnP.h"
 #include "PltMediaItem.h"
 #include "PltService.h"
@@ -40,11 +42,15 @@
 #include <QUrl>
 #include <QList>
 #include <QMap>
-#include <QDebug>
+#include <QImage>
+#include <QByteArray>
+#include <QBuffer>
 
 // Local includes
 
 #include "digikam_debug.h"
+#include "previewloadthread.h"
+#include "dimg.h"
 
 NPT_SET_LOCAL_LOGGER("digiKam.media.server.delegate")
 
@@ -661,7 +667,98 @@ NPT_Result DLNAMediaServerDelegate::ServeFile(const NPT_HttpRequest&        requ
                                               NPT_HttpResponse&             response,
                                               const NPT_String&             file_path)
 {
-    NPT_CHECK_WARNING(PLT_HttpServer::ServeFile(request, context, response, file_path));
+    // Try to stream image file as transcoded preview.
+    // This will serve image in reduced size, including all know image formats
+    // supported by digiKam core, as JPEG, PNG, TIFF, and RAW files for ex.
+
+    DImg dimg = PreviewLoadThread::loadFastSynchronously(QString::fromUtf8(file_path.GetChars()), 2048);
+
+    if (dimg.isNull())
+    {
+        // Not a supported image format. Try to stream file as well, without transcoding.
+        // TODO : support video file as transcoded video stream using QtAV (if possible).
+
+        NPT_CHECK_WARNING(PLT_HttpServer::ServeFile(request, context, response, file_path));
+        return NPT_SUCCESS;
+    }
+
+    // This code is basically the same than PLT_HttpServer::ServeFile() excepted the
+    // image trancoding pass served as byte stream.
+
+    NPT_InputStreamReference stream;
+    NPT_File                 file(file_path);
+    NPT_FileInfo             file_info;
+
+    // prevent hackers from accessing files outside of our root
+
+    if ((file_path.Find("/..") >= 0)  ||
+        (file_path.Find("\\..") >= 0) ||
+        NPT_FAILED(NPT_File::GetInfo(file_path, &file_info)))
+    {
+        return NPT_ERROR_NO_SUCH_ITEM;
+    }
+
+    // check for range requests
+
+    const NPT_String* range_spec = request.GetHeaders().GetHeaderValue(NPT_HTTP_HEADER_RANGE);
+
+    // handle potential 304 only if range header not set
+
+    NPT_DateTime  date;
+    NPT_TimeStamp timestamp;
+
+    if (NPT_SUCCEEDED(PLT_UPnPMessageHelper::GetIfModifiedSince((NPT_HttpMessage&)request, date)) &&
+        !range_spec)
+    {
+        date.ToTimeStamp(timestamp);
+
+        NPT_LOG_INFO_5("File %s timestamps: request=%d (%s) vs file=%d (%s)", 
+                       (const char*)request.GetUrl().GetPath(),
+                       (NPT_UInt32)timestamp.ToSeconds(),
+                       (const char*)date.ToString(),
+                       (NPT_UInt32)file_info.m_ModificationTime,
+                       (const char*)NPT_DateTime(file_info.m_ModificationTime).ToString());
+
+        if (timestamp >= file_info.m_ModificationTime)
+        {
+            // it's a match
+
+            NPT_LOG_FINE_1("Returning 304 for %s", request.GetUrl().GetPath().GetChars());
+            response.SetStatus(304, "Not Modified", NPT_HTTP_PROTOCOL_1_1);
+            return NPT_SUCCESS;
+        }
+    }
+
+    // Trancoding image as preview.
+
+    QImage preview = dimg.copyQImage();
+    QByteArray ba;
+    QBuffer    buffer(&ba);
+    buffer.open(QIODevice::WriteOnly);
+    preview.save(&buffer, "JPG");
+    buffer.close();
+
+    stream         = new NPT_MemoryStream(ba.data(), (NPT_Size)ba.size());
+
+    if (stream.IsNull())
+    {
+        return NPT_ERROR_NO_SUCH_ITEM;
+    }
+
+    // set Last-Modified and Cache-Control headers
+
+    if (file_info.m_ModificationTime)
+    {
+        NPT_DateTime last_modified = NPT_DateTime(file_info.m_ModificationTime);
+        response.GetHeaders().SetHeader("Last-Modified", last_modified.ToString(NPT_DateTime::FORMAT_RFC_1123), true);
+        response.GetHeaders().SetHeader("Cache-Control", "max-age=0,must-revalidate", true);
+    }
+
+    PLT_HttpRequestContext tmp_context(request, context);
+
+    NPT_CHECK_WARNING(PLT_HttpServer::ServeStream(request, context, response, stream,
+                      "application/octet-stream"));
+
     return NPT_SUCCESS;
 }