Hi Ali,
Background picture file is loaded into memory bitmap file, which is attached to memory device context -- a kind of invisible form (Delphi people even call it
Canvas).
When a part or the whole _SCREEN needs to be redrawn, Windows copies corresponding pixels from that memory bitmap. Usually this process of copying data from
memory Canvas to
_SCREEN Canvas is extremely fast and high-prioritised.
When you set
_SCREEN.picture = somefile.JPG, FoxPro reads this file from disk, and converts it into memory bitmap.
When you set
_SCREEN.picture = somefile.BMP, FoxPro reads this file from disk -- it may take longer time comparing to reading smaller JPEG. This is the most degrading of performance you can expect. IMHO :)
After all in both cases same memory bitmap is created. May be the
Bits Per Pixel value is important too, though I do not think so.