I need to add my own custom file-extension .myext to the Windows system file-types which are automatically previewed in Windows File Explorer as images in the Thumbnail view (like any other image types e.g. .png).
PLEASE NOTE: .myext files are obtained by simply RENAMING the extension of an existing .png file from .png to .myext (which should make it unnecessary to implement my own custom thumbnail handler).
So I tried the following: in the Windows Registry key Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\KindMap I added this value: .myext REG_SZ picture. Then I rebooted Windows. But the .myext files are still not viewed as image in Windows File Explorer's Thumbnails view.
So how can I preview .myext files (which as I said are renamed .png files) in Windows File Explorer's Thumbnails view?