[Lazarus] TAChart with transparent background

[Werner Pamler]

I added some simple time measuring code (using GetTickCount) to the 
background image tutorial to see the speed loss that you mention: 
Without the backgrounds (Lazarus logo and gradient) the GetTickCount 
reports 0 ms between the OnBeforeDrawBackground and OnAfterPaint events, 
while with the backgrounds it reports 16 ms, sometimes 0 ms. Replacing 
the StretchDraw by a simple Draw in the painting of the logo,  brings 
down the time also to 0. Therefore I'd guess that the background 
painting is not perceivable unless you squeeze a 20 mega-pixel photo 
into the chart area or load the image during the painting event.

What exactly are you doing?