Psychtoolbox>PsychCV.{mex*} subfunction

[inputImageMemBuffer] = PsychCV(‘AprilInitialize’, tagFamilyName, imgWidth, imgHeight, imgChannels [, imgFormat][, maxNrTags]);

Initialize apriltag prior to first use.

Apriltag markers are loaded for the given apriltag family ‘tagFamilyName’.
The following tag families are currently supported:
tag36h11
tag25h9
tag16h5
tagCircle21h7
tagCircle49h12 - Use maxNrTags to restrict size!
tagCustom48h12 - Use maxNrTags to restrict size!
tagStandard41h12
tagStandard52h13 - Use maxNrTags to restrict size!

Internal video image memory buffers are set up for input images of size
‘imgWidth’ x ‘imgHeight’ pixels, with ‘imgChannels’ mono or color channels (1
MONO, 3 RGB, or 4 RGBA are valid settings, but 1 for MONO is the most efficient
choice for minimal computation time). For 3 or 4 channels, the input color
format ‘imgFormat’ (or a default setting if ‘imgFormat’ is omitted) defines
color channel ordering for the input pixel bytes. ‘imgFormat’ can be one of:
RGB = 1, BGR = 2, BGRA = 4 (default for 4 channels), ARGB = 7, MONO = 6. Other
pixel formats are not supported for input images, but these are the ones
provided by Psychtoolbox’s various video capture engines for different video
sources and settings. For 1 channel mono/grayscale or 3 channel RGB color
content, you don’t need to specify ‘imgFormat’ as the chosen default will always
work, but for 4 channel content with alpha channel, you may have to specify
‘imgFormat’ if your machine does not return BGRA ordered pixels, but ARGB
ordered pixels, or marker detection on 4 channel content may fail or perform
poorly.
When using a tag family with many potential tags, you can limit the number of
tags to use to the first ‘maxNrTags’ tags if you specify ‘maxNrTags’. This is
important for certain large tag families, as using the tag family at its full
capacity may consume a lot of memory and take a very long time to initialize!
Then apriltags is initialized, and a memory buffer handle ‘inputImageMemBuffer’
to the internal video memory input buffer is returned.

You should pass this handle to Psychtoolbox functions for videocapture to
acquire video images from the scene containing the tags, and to store that input
image inside PsychCV’s video buffer.

After this step, you can commence the actual tracking operations by calls to
Screen()’s video capture engine and the PsychCV(‘AprilDetectMarkers’, …);
subfunction.

###See also: AprilShutdown AprilDetectMarkers AprilSettings April3DSettings