diff --git a/modules/gui/qt/Makefile.am b/modules/gui/qt/Makefile.am
index 1b9b513b3895888667e12397b68cf4be7ed21b83..e9ecfa16f8622040d1fda7801cc30574c9e89b2f 100644
--- a/modules/gui/qt/Makefile.am
+++ b/modules/gui/qt/Makefile.am
@@ -218,6 +218,8 @@ libqt_plugin_la_SOURCES = \
gui/qt/util/audio_device_model.cpp \
gui/qt/util/audio_device_model.hpp \
gui/qt/util/color_scheme_model.cpp gui/qt/util/color_scheme_model.hpp \
+ gui/qt/util/covergenerator.cpp \
+ gui/qt/util/covergenerator.hpp \
gui/qt/util/imageluminanceextractor.cpp gui/qt/util/imageluminanceextractor.hpp \
gui/qt/util/imagehelper.cpp gui/qt/util/imagehelper.hpp \
gui/qt/util/i18n.cpp gui/qt/util/i18n.hpp \
@@ -374,6 +376,7 @@ nodist_libqt_plugin_la_SOURCES = \
gui/qt/util/asynctask.moc.cpp \
gui/qt/util/audio_device_model.moc.cpp \
gui/qt/util/color_scheme_model.moc.cpp \
+ gui/qt/util/covergenerator.moc.cpp \
gui/qt/util/imageluminanceextractor.moc.cpp \
gui/qt/util/i18n.moc.cpp \
gui/qt/util/listcache.moc.cpp \
diff --git a/modules/gui/qt/util/covergenerator.cpp b/modules/gui/qt/util/covergenerator.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..dcb61d22f870571c4b846f4237f381bde3bfaf42
--- /dev/null
+++ b/modules/gui/qt/util/covergenerator.cpp
@@ -0,0 +1,379 @@
+/*****************************************************************************
+ * Copyright (C) 2021 VLC authors and VideoLAN
+ *
+ * Authors: Benjamin Arnaud <bunjee@omega.gg>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * ( at your option ) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+
+#include "covergenerator.hpp"
+
+// VLC includes
+#include "qt.hpp"
+
+// MediaLibrary includes
+#include "medialibrary/mlhelper.hpp"
+
+// Qt includes
+#include <QDir>
+#include <QGraphicsScene>
+#include <QGraphicsPixmapItem>
+#include <QGraphicsBlurEffect>
+
+//-------------------------------------------------------------------------------------------------
+// Static variables
+
+static const QString COVERGENERATOR_STORAGE = "/art/qt-covers";
+
+static const int COVERGENERATOR_COUNT = 2;
+
+static const QString COVERGENERATOR_DEFAULT = ":/noart.png";
+
+//-------------------------------------------------------------------------------------------------
+// Ctor / dtor
+//-------------------------------------------------------------------------------------------------
+
+CoverGenerator::CoverGenerator(vlc_medialibrary_t * ml, const MLItemId & itemId, int index)
+ : m_ml(ml)
+ , m_id(itemId)
+ , m_index(index)
+ , m_countX(COVERGENERATOR_COUNT)
+ , m_countY(COVERGENERATOR_COUNT)
+ , m_split(Divide)
+ , m_smooth(false)
+ , m_blur(0)
+ , m_default(COVERGENERATOR_DEFAULT) {}
+
+//-------------------------------------------------------------------------------------------------
+// Interface
+//-------------------------------------------------------------------------------------------------
+
+/* Q_INVOKABLE */ MLItemId CoverGenerator::getId()
+{
+ return m_id;
+}
+
+/* Q_INVOKABLE */ int CoverGenerator::getIndex()
+{
+ return m_index;
+}
+
+//-------------------------------------------------------------------------------------------------
+
+/* Q_INVOKABLE */ void CoverGenerator::setSize(const QSize & size)
+{
+ m_size = size;
+}
+
+/* Q_INVOKABLE */ void CoverGenerator::setCountX(int x)
+{
+ m_countX = x;
+}
+
+/* Q_INVOKABLE */ void CoverGenerator::setCountY(int y)
+{
+ m_countY = y;
+}
+
+/* Q_INVOKABLE */ void CoverGenerator::setSplit(Split split)
+{
+ m_split = split;
+}
+
+/* Q_INVOKABLE */ void CoverGenerator::setSmooth(bool enabled)
+{
+ m_smooth = enabled;
+}
+
+/* Q_INVOKABLE */ void CoverGenerator::setBlur(int radius)
+{
+ m_blur = radius;
+}
+
+/* Q_INVOKABLE */ void CoverGenerator::setDefaultThumbnail(const QString & fileName)
+{
+ m_default = fileName;
+}
+
+//-------------------------------------------------------------------------------------------------
+// QRunnable implementation
+//-------------------------------------------------------------------------------------------------
+
+QString CoverGenerator::execute() /* override */
+{
+ QDir dir(config_GetUserDir(VLC_CACHE_DIR) + COVERGENERATOR_STORAGE);
+
+ dir.mkpath(dir.absolutePath());
+
+ vlc_ml_parent_type type = m_id.type;
+
+ int64_t id = m_id.id;
+
+ QString string = getStringType(type);
+
+ QString fileName = QString("%1_thumbnail_%2.jpg").arg(string).arg(id);
+
+ fileName = dir.absoluteFilePath(fileName);
+
+ if (dir.exists(fileName))
+ {
+ return fileName;
+ }
+
+ QStringList thumbnails;
+
+ int count = m_countX * m_countY;
+
+ if (type == VLC_ML_PARENT_GENRE)
+ thumbnails = getGenre(count, id);
+ else
+ thumbnails = getMedias(count, id, type);
+
+ if (thumbnails.isEmpty())
+ {
+ if (m_split == CoverGenerator::Duplicate)
+ {
+ while (thumbnails.count() != count)
+ {
+ thumbnails.append(m_default);
+ }
+ }
+ else
+ {
+ thumbnails.append(m_default);
+
+ m_countX = 1;
+ m_countY = 1;
+ }
+ }
+ else if (m_split == CoverGenerator::Duplicate)
+ {
+ int index = 0;
+
+ while (thumbnails.count() != count)
+ {
+ thumbnails.append(thumbnails.at(index));
+
+ index++;
+ }
+ }
+ else // if (m_split == CoverGenerator::Divide)
+ {
+ // NOTE: This handles the 2x2 case.
+ if (thumbnails.count() == 2)
+ {
+ m_countX = 2;
+ m_countY = 1;
+ }
+ }
+
+ QImage image(m_size, QImage::Format_RGB32);
+
+ image.fill(Qt::white);
+
+ QPainter painter;
+
+ painter.begin(&image);
+
+ draw(painter, thumbnails);
+
+ painter.end();
+
+ if (m_blur > 0)
+ blur(&image);
+
+ image.save(fileName, "jpg");
+
+ return fileName;
+}
+
+//-------------------------------------------------------------------------------------------------
+// Private functions
+//-------------------------------------------------------------------------------------------------
+
+void CoverGenerator::draw(QPainter & painter, const QStringList & fileNames)
+{
+ int count = fileNames.count();
+
+ int width = m_size.width() / m_countX;
+ int height = m_size.height() / m_countY;
+
+ for (int y = 0; y < m_countY; y++)
+ {
+ for (int x = 0; x < m_countX; x++)
+ {
+ int index = m_countX * y + x;
+
+ if (index == count) return;
+
+ QRect rect;
+
+ // NOTE: This handles the wider thumbnail case (e.g. for a 2x1 grid).
+ if (index == count - 1 && x != m_countX - 1)
+ {
+ rect = QRect(width * x, height * y, width * m_countX - x, height);
+ }
+ else
+ rect = QRect(width * x, height * y, width, height);
+
+ drawImage(painter, fileNames.at(index), rect);
+ }
+ }
+}
+
+void CoverGenerator::drawImage(QPainter & painter, const QString & fileName, const QRect & target)
+{
+ QImage image;
+
+ if (fileName.isEmpty())
+ image.load(m_default);
+ else
+ image.load(fileName);
+
+ // NOTE: This image does not seem valid so we paint the placeholder instead.
+ if (image.isNull())
+ {
+ image.load(m_default);
+ }
+
+ // NOTE: Should we use Qt::SmoothTransformation or favor efficiency ?
+ if (m_smooth)
+ image = image.scaled(target.size(), Qt::KeepAspectRatioByExpanding,
+ Qt::SmoothTransformation);
+ else
+ image = image.scaled(target.size(), Qt::KeepAspectRatioByExpanding);
+
+ int x = (image.width () - target.width ()) / 2;
+ int y = (image.height() - target.height()) / 2;
+
+ QRect source(x, y, target.width(), target.height());
+
+ painter.drawImage(target, image, source);
+}
+
+//-------------------------------------------------------------------------------------------------
+
+// FIXME: This implementation is not ideal and uses a dedicated QGraphicsScene.
+void CoverGenerator::blur(QImage * image)
+{
+ assert(image);
+
+ QGraphicsScene scene;
+
+ QGraphicsPixmapItem item(QPixmap::fromImage(*image));
+
+ QGraphicsBlurEffect effect;
+
+ effect.setBlurRadius(m_blur);
+
+ effect.setBlurHints(QGraphicsBlurEffect::QualityHint);
+
+ item.setGraphicsEffect(&effect);
+
+ scene.addItem(&item);
+
+ QImage result(image->size(), QImage::Format_ARGB32);
+
+ QPainter painter(&result);
+
+ scene.render(&painter);
+
+ *image = result;
+}
+
+//-------------------------------------------------------------------------------------------------
+
+QString CoverGenerator::getStringType(vlc_ml_parent_type type) const
+{
+ switch (type)
+ {
+ case VLC_ML_PARENT_GENRE:
+ return "genre";
+ case VLC_ML_PARENT_GROUP:
+ return "group";
+ case VLC_ML_PARENT_PLAYLIST:
+ return "playlist";
+ default:
+ return "unknown";
+ }
+}
+
+//-------------------------------------------------------------------------------------------------
+
+QStringList CoverGenerator::getGenre(int count, int64_t id) const
+{
+ QStringList thumbnails;
+
+ vlc_ml_query_params_t params;
+
+ memset(¶ms, 0, sizeof(vlc_ml_query_params_t));
+
+ // NOTE: We retrieve twice the count to maximize our chances to get a valid thumbnail.
+ params.i_nbResults = count * 2;
+
+ ml_unique_ptr<vlc_ml_album_list_t> list(vlc_ml_list_genre_albums(m_ml, ¶ms, id));
+
+ for (const vlc_ml_album_t & album : ml_range_iterate<vlc_ml_album_t>(list))
+ {
+ if (album.thumbnails[VLC_ML_THUMBNAIL_SMALL].i_status != VLC_ML_THUMBNAIL_STATUS_AVAILABLE)
+ continue;
+
+ QUrl url(album.thumbnails[VLC_ML_THUMBNAIL_SMALL].psz_mrl);
+
+ // NOTE: We only want local files to compose the cover.
+ if (url.isLocalFile() == false)
+ continue;
+
+ thumbnails.append(url.path());
+
+ if (thumbnails.count() == count)
+ return thumbnails;
+ }
+
+ return thumbnails;
+}
+
+QStringList CoverGenerator::getMedias(int count, int64_t id, vlc_ml_parent_type type) const
+{
+ QStringList thumbnails;
+
+ vlc_ml_query_params_t params;
+
+ memset(¶ms, 0, sizeof(vlc_ml_query_params_t));
+
+ // NOTE: We retrieve twice the count to maximize our chances to get a valid thumbnail.
+ params.i_nbResults = count * 2;
+
+ ml_unique_ptr<vlc_ml_media_list_t> list(vlc_ml_list_media_of(m_ml, ¶ms, type, id));
+
+ for (const vlc_ml_media_t & media : ml_range_iterate<vlc_ml_media_t>(list))
+ {
+ if (media.thumbnails[VLC_ML_THUMBNAIL_SMALL].i_status != VLC_ML_THUMBNAIL_STATUS_AVAILABLE)
+ continue;
+
+ QUrl url(media.thumbnails[VLC_ML_THUMBNAIL_SMALL].psz_mrl);
+
+ // NOTE: We only want local files to compose the cover.
+ if (url.isLocalFile() == false)
+ continue;
+
+ thumbnails.append(url.path());
+
+ if (thumbnails.count() == count)
+ return thumbnails;
+ }
+
+ return thumbnails;
+}
diff --git a/modules/gui/qt/util/covergenerator.hpp b/modules/gui/qt/util/covergenerator.hpp
new file mode 100644
index 0000000000000000000000000000000000000000..443d2a02aec61dfdb541e45c7eee924129deab02
--- /dev/null
+++ b/modules/gui/qt/util/covergenerator.hpp
@@ -0,0 +1,114 @@
+/*****************************************************************************
+ * Copyright (C) 2021 VLC authors and VideoLAN
+ *
+ * Authors: Benjamin Arnaud <bunjee@omega.gg>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * ( at your option ) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+
+#ifndef COVERGENERATOR_HPP
+#define COVERGENERATOR_HPP
+
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+// MediaLibrary includes
+#include "medialibrary/mlqmltypes.hpp"
+
+// Util includes
+#include "util/asynctask.hpp"
+
+// Qt includes
+#include <QPainter>
+
+// Forward declarations
+class vlc_medialibrary_t;
+class MLItemId;
+
+class CoverGenerator : public AsyncTask<QString>
+{
+ Q_OBJECT
+
+ Q_ENUMS(Split)
+
+public: // Enums
+ enum Split
+ {
+ Divide,
+ Duplicate
+ };
+
+public:
+ CoverGenerator(vlc_medialibrary_t * ml, const MLItemId & itemId, int index = -1);
+
+public: // Interface
+ Q_INVOKABLE MLItemId getId();
+
+ Q_INVOKABLE int getIndex();
+
+ Q_INVOKABLE void setSize(const QSize & size);
+
+ Q_INVOKABLE void setCountX(int x);
+ Q_INVOKABLE void setCountY(int y);
+
+ // NOTE: Do we want to divide or duplicate thumbnails to reach the proper count ?
+ Q_INVOKABLE void setSplit(Split split);
+
+ // NOTE: Applies SmoothTransformation to thumbnails. Disabled by default.
+ Q_INVOKABLE void setSmooth(bool enabled);
+
+ // NOTE: You need to specify a radius to enable blur, 8 looks good.
+ Q_INVOKABLE void setBlur(int radius);
+
+ Q_INVOKABLE void setDefaultThumbnail(const QString & fileName);
+
+public: // AsyncTask implementation
+ QString execute() override;
+
+private: // Functions
+ void draw(QPainter & painter, const QStringList & fileNames);
+
+ void drawImage(QPainter & painter, const QString & fileName, const QRect & rect);
+
+ void blur(QImage * image);
+
+ QString getStringType(vlc_ml_parent_type type) const;
+
+ QStringList getMedias(int count, int64_t id, vlc_ml_parent_type type) const;
+ QStringList getGenre (int count, int64_t id) const;
+
+private:
+ vlc_medialibrary_t * m_ml;
+
+ MLItemId m_id;
+
+ int m_index;
+
+ QSize m_size;
+
+ int m_countX;
+ int m_countY;
+
+ Split m_split;
+
+ bool m_smooth;
+
+ int m_blur;
+
+ QString m_default;
+};
+
+#endif // COVERGENERATOR_HPP
diff --git a/po/POTFILES.in b/po/POTFILES.in
index 00a6e62aabd8c6b94e49535cb66118cbdabbfe7c..b13f49b29cff00727649e85b6240c42a09fbfa3f 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -791,6 +791,8 @@ modules/gui/qt/widgets/native/animators.cpp
modules/gui/qt/widgets/native/animators.hpp
modules/gui/qt/widgets/native/customwidgets.cpp
modules/gui/qt/widgets/native/customwidgets.hpp
+modules/gui/qt/util/covergenerator.cpp
+modules/gui/qt/util/covergenerator.hpp
modules/gui/qt/util/imagehelper.cpp
modules/gui/qt/util/imagehelper.hpp
modules/gui/qt/util/qt_dirs.cpp