diff --git a/libxisf.cpp b/libxisf.cpp
index a5097b1..003e361 100644
--- a/libxisf.cpp
+++ b/libxisf.cpp
@@ -400,6 +400,11 @@ void *Image::imageData()
     return _dataBlock.data.data();
 }
 
+const void *Image::imageData() const
+{
+    return _dataBlock.data.data();
+}
+
 size_t Image::imageDataSize() const
 {
     return _dataBlock.data.size();
diff --git a/libxisf.h b/libxisf.h
index d8ef683..98edaf6 100644
--- a/libxisf.h
+++ b/libxisf.h
@@ -169,8 +169,11 @@ public:
     bool addFITSKeywordAsProperty(const QString &name, const QVariant &value);
 
     void* imageData();
+    const void* imageData() const;
     template<typename T>
     T* imageData(){ return static_cast<T*>(imageData()); }
+    template<typename T>
+    const T* imageData() const { return static_cast<T*>(imageData()); }
     size_t imageDataSize() const;
     DataBlock::CompressionCodec compression() const;
     void setCompression(DataBlock::CompressionCodec compression, int level = -1);