openmv/apriltag
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INSTALL
=======
The default installation will place headers in /usr/local/include and
shared library in /usr/local/lib. It also installs a pkg-config script
into /usr/local/lib/pkgconfig.
$ make
$ sudo make install
To install to a different directory than /usr/local:
$ PREFIX=/some/path sudo make install
USAGE
=====
A basic AprilTag application can be seen in example/apriltag_demo.c.
Initialization: instantiate a detector and at least one tag family.
apriltag_detector_t *td = apriltag_detector_create();
apriltag_family_t *tf = tag36h11_create();
apriltag_detector_add_family(td, tf);
Some tag detector parameters can be set at this time.
The default parameters are the recommended starting point.
td->quad_decimate = 1.0;
td->quad_sigma = 0.0;
td->refine_edges = 1;
td->refine_decode = 0;
td->refine_pose = 0;
Increase the image decimation if faster processing is required; the
trade-off is a slight decrease in detection range. A factor of 1.0
means the full-size input image is used.
Some Gaussian blur (quad_sigma) may help with noisy input images.
Detection: a single one-line call will process an input image
and return a list of detections.
zarray_t *detections = apriltag_detector_detect(td, im);
for (int i = 0; i < zarray_size(detections); i++) {
apriltag_detection_t *det;
zarray_get(detections, i, &det);
// Do something with det here
}
apriltag_detections_destroy(detections);
zarray is a container class which is included with apriltag.
To process through the list of detections, use zarray_get,
as illustrated above.
The caller is responsible for freeing detections by calling
apriltag_detections_destroy().
Cleanup: free the detector and tag family when done.
apriltag_detector_destroy(td);
tag36h11_destroy(tf);
OPENCV INTEGRATION
==================
Note that this library has no external dependencies. Most applications
will require, at minimum, a method for acquiring images.
See example/opencv_demo.cc for an example of using AprilTag in C++ with OpenCV.
This example application can be built by executing the following:
$ cd examples
$ make opencv_demo
Image data in a cv::Mat object can be passed to AprilTag without creating
a deep copy. Simply create an image_u8_t header for the cv::Mat data buffer:
cv::Mat img;
image_u8_t img_header = { .width = img.cols,
.height = img.rows,
.stride = img.cols,
.buf = img.data
};