VoverlaX User Manual
Page 11
Version 1.0.0.2
(3) Clear Old Overlay Value
This box is only meaningful when box “
Transparent
” is also ticked:
If
Clear Old Overlay Value
is ticked, then those pixels in the graphics file whose colour values and the
“
Transparency Colour
” have the minimum difference (as described in the “
Transparency Colour
” above)
will become totally transparent, i.e., the video underneath them will be exposed.
If this box
is
cleared, then those pixels in the graphics file whose colour values and the “
Transparency
Colour
” have minimum difference as described in the “
Transparency Colour
” above will combine (logical or)
their old alpha value with the new alpha value on screen, so that if the resulting alpha is nonzero then some
degree of overlay will appear on top of the video – this is useful for example to display an half-transparent
background exposing some of the video underneath. The following are examples using the same graphics file
with red text
ABCD
in front of a white background, and
Transparency Colour
is white,
Alpha Start
/
Alpha
End
are 128:
(1)
Transparent
and
Clear Old Overlay
Value
Ticked (2)
Transparent
Ticked,
Clear Old Overlay
Value
Cleared
(4)
Raster Operation
This controls how the pixels of the graphics file will be combined with the overlay pixels already being
displayed on the same position by previous Overlay operations(if there is any): SRCCOPY means the
new pixels completely replace the original pixel, SRCAND means the new pixels do logical AND with
the original pixels, the BLACKNESS means display black at the positions, etc.
Alpha
change,
X/Y
change, duration, etc parameters have the same meaning as in
Text
and
Timer
items.
Graphics File Item
has no “
AlphaBk
” parameter since it has not background colour.
