Screen('OpenOffscreenWindow')

Psychtoolbox › Screen.{mex*,dll} subfunction

Open an offscreen window. This is simply an OpenGL texture that is treated as a
window, so you can draw to it. Offscreen windows should be only used to keep old
code from OS-9 Psychtoolbox working or if you need to draw to them fast. For
quickly displaying images, please use the 'MakeTexture' and 'DrawTexture'
commands. They allow for significantly higher drawing speeds. You can specify a
screen (any windowPtr or a screenNumber>=0) or no screen(screenNumber=-1), but
any real screen must already have an open Screen window when you call
OpenOffscreenWindow. "color" is the clut index (scalar or [r g b] triplet or [r
g b a] quadruple) that you want to poke into each pixel as initial background
color; default is white. "rect" specifies the size of the offscreen window If
supplied, "rect" must contain at least one pixel. If a windowPtr is supplied,
then "rect" defaults to the whole window. If a screenNumber is supplied then
"rect" defaults to the whole screen. If a screenNumber of -1 is supplied, then
"rect" defaults to the size of the main screen. (In all cases, subsequent
references to this new offscreen window will use its coordinates: origin at its
upper left.) "pixelSize" sets the depth (in bits) of each pixel. If you specify
no screen (screenNumber=-1) then the default pixelSize is 32, but you can
specify any legal depth: 8, 16, 24, 32. A pixelSize of 0 or [] is replaced by
the default of 32 bits per pixel. If you specify a screen number of windowPtr,
then the default depth is that of the screen or window. If you run your script
with the imaging pipeline enabled (imagingmode flag > 0 in Screen('OpenWindow'),
then all Offscreen windows always have 4 color channels RGBA and the selectable
depths are additionally 64 bits or 128 bits, corresponding to 16 bits or 32 bits
floating point precision per color compponent.
'specialFlags' optional parameter to set special properties, defaults to zero.
If you set it to 2 then the offscreen window will be drawn with especially high
precision, see specialFlags setting of 2 in help for Screen('DrawTexture') for
more explanation.
'multiSample' optional number of samples to use for anti-aliased drawing: This
defaults to zero if omitted, ie., no anti-aliasing is performed when drawing
into this offscreen window. If you set a positive non-zero number of samples and
your system supports anti-aliased drawing to offscreen windows and the imaging
pipeline is active, then Screen will try to allocate the offscreen window with
at least the requested number of samples per pixel for anti-aliasing, but
gracefully fall back to lower numbers if the hardware isn't capable of handling
the requested number. Please note that anti-aliased offscreen windows can't be
directly used for transformations in Screen('TransformTexture') or for drawing
via Screen('DrawTexture') -- this is a hardware limitation. To display or use
the content of an anti-aliased offscreen window you must first create a normal
offscreen window of the same size and color format (same 'rect' and 'pixelSize'
parameter), then use Screen('CopyWindow', antialiasedWindowhandle,
normalWindowhandle); to copy the content to the normal offscreen window. This
will perform the actual conversion into anti-aliased and displayable content.
If the imaging pipeline is disabled, the 'multiSample' parameter will be
silently ignored.
NOTE: Screen's windows are known only to Screen and must be closed by it, e.g.,
Screen('Close', w). Matlab knows nothing about Screen's windows, so the Matlab
CLOSE command won't work on Screen's windows.