Add Farbfeld read only support

src/imageformats/ff_p.h

@@ -0,0 +1,42 @@
+/*
+    This file is part of the KDE project
+    SPDX-FileCopyrightText: 2026 Mirco Miranda <mircomir@outlook.com>
+
+    SPDX-License-Identifier: LGPL-2.0-or-later
+*/
+
+#ifndef KIMG_FF_P_H
+#define KIMG_FF_P_H
+
+#include <QImageIOPlugin>
+#include <QScopedPointer>
+
+class FFHandlerPrivate;
+class FFHandler : public QImageIOHandler
+{
+public:
+    FFHandler();
+
+    bool canRead() const override;
+    bool read(QImage *image) override;
+
+    bool supportsOption(QImageIOHandler::ImageOption option) const override;
+    QVariant option(QImageIOHandler::ImageOption option) const override;
+
+    static bool canRead(QIODevice *device);
+
+private:
+    const QScopedPointer<FFHandlerPrivate> d;
+};
+
+class FFPlugin : public QImageIOPlugin
+{
+    Q_OBJECT
+    Q_PLUGIN_METADATA(IID "org.qt-project.Qt.QImageIOHandlerFactoryInterface" FILE "ff.json")
+
+public:
+    Capabilities capabilities(QIODevice *device, const QByteArray &format) const override;
+    QImageIOHandler *create(QIODevice *device, const QByteArray &format = QByteArray()) const override;
+};
+
+#endif // KIMG_FF_P_H