If you are using multiple Layers, then layer changes will also trigger OnImageChange.
Note: ◼This event is triggered by editing methods in TImageEnProc or in TImageEnView (e.g. Clear). Not by changes to the IEBitmap ◼TImageEnProc calls ImageChange after a modification which actuates OnImageChange. ◼The OnImageChangeEx event is also available, which is the same except that it includes a parameter showing whether the change is due to the image or layers