Add support for saving embedded album covers

Fixes #286

src/core/imageutils.h

@@ -0,0 +1,51 @@
+/*
+ * Strawberry Music Player
+ * Copyright 2019, Jonas Kvinge <jonas@jkvinge.net>
+ *
+ * Strawberry 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 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Strawberry 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 Strawberry.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef IMAGEUTILS_H
+#define IMAGEUTILS_H
+
+#include "config.h"
+
+#include <QList>
+#include <QByteArray>
+#include <QString>
+#include <QStringList>
+#include <QUrl>
+#include <QImage>
+#include <QPixmap>
+
+class ImageUtils {
+
+ private:    
+  static QStringList kSupportedImageMimeTypes;
+  static QStringList kSupportedImageFormats;
+
+ public:
+  static QStringList SupportedImageMimeTypes();
+  static QStringList SupportedImageFormats();
+  static QList<QByteArray> ImageFormatsForMimeType(const QByteArray &mimetype);
+  static QByteArray SaveImageToJpegData(const QImage &image = QImage());
+  static QPixmap TryLoadPixmap(const QUrl &automatic, const QUrl &manual, const QUrl &url = QUrl());
+  static QImage ScaleAndPad(const QImage &image, const bool scale, const bool pad, const int desired_height);
+  static QImage CreateThumbnail(const QImage &image, const bool pad, const QSize size);
+  static QImage GenerateNoCoverImage(const QSize size = QSize());
+
+};
+
+#endif  // IMAGEUTILS_H