[Closed] Updating a bitmap

Hi everyone,

I have an issue with saving and loading bitmaps with maxscript.
I’m grabing the viewport and saving it to a bitmap.
Later I load the saved bitmap and show it as a thumbnail in my UI.
I allow updating the thumbnail by grabing the viewport again and saving it over the existing file.
Now I want to refresh the thumbnail in the UI by reloading the bitmap from the file.
The problem is it still shows the first bitmap. If I open the saved file, I can see the new bitmap, but in the UI I see the old bitmap. The new bitmap is shown only after a Max restart.

Here is a small snipet that shows the problem:

(
	global roll_Test
	try (destroyDialog roll_Test) catch ()
	rollout roll_Test "Test"
	(
		
		local thumbFileName
		local BITMAP_SIZE = [200, 120]
		
	-- User Interface
	------------------------------------------
		
		imgTag imtThumb "" width:BITMAP_SIZE.x height:BITMAP_SIZE.y align:#center style:#bmp_center transparent:red
		button btnUpdate "Update"
	
	-- Functions
	------------------------------------------
	
		fn grabThumbnail =
		(
			local grab = gw.getViewportDib()
			local thumbnail = bitmap BITMAP_SIZE.x BITMAP_SIZE.y filename:thumbFileName
			
			copy grab thumbnail
			save thumbnail quiet:true
			close thumbnail
			
			local preview = openBitMap thumbFileName
			imtThumb.bitmap = preview
		)
		
		fn openDialog =
		(
			createDialog roll_Test width:(BITMAP_SIZE.x + 20)
		)
	
		fn init =
		(
			thumbFileName = getDir #temp + "\\Test_Bitmap_1.jpg"
			grabThumbnail()
		)
		
		fn done =
		(
			deleteFile thumbFileName
		)
	
	-- Event Handlers
	------------------------------------------
	
		on roll_Test open do init()
		on roll_Test close do done()
		on btnUpdate pressed do grabThumbnail()
		on imtThumb dblclick do HiddenDosCommand ("\"" + thumbFileName + "\"")
	
	)
	
	roll_Test.openDialog()
)

Notice that when you hit the ‘Update’ button it will grab a new viewport snapshot and save it in the same file. Then it will attempt to update the thumbnail from the file (it must be from the file and not from the gw grab).
Double clicking the thumbnail will open the image in the default image viewer, where you can see the file was updated sucessfully. But somehow max ignores the update.

Any idea why or how to fix it?