rectangleAsync function
Rectangle draws a simple, thick, or filled up-right rectangle. It renders a rectangle with the desired characteristics to the target Mat image.
For further details, please see: https:///docs.opencv.org/master/d6/d6e/group__imgproc__draw.html#ga07d2f74cadcf8e305e810ce8eed13bc9
Implementation
Future<Mat> rectangleAsync(
InputOutputArray img,
Rect rect,
Scalar color, {
int thickness = 1,
int lineType = LINE_8,
int shift = 0,
}) async =>
cvRunAsync0(
(callback) => cffi.RectangleWithParams_Async(
img.ref, rect.ref, color.ref, thickness, lineType, shift, callback),
(completer) => completer.complete(img),
);