private MatOfPoint OrderCornerPoints(MatOfPoint corners)
{
if (corners.size().area() <= 0 || corners.rows() < 4)
{
return(corners);
}
// rearrange the points in the order of upper left, upper right, lower right, lower left.
using (Mat x = new Mat(corners.size(), CvType.CV_32SC1))
using (Mat y = new Mat(corners.size(), CvType.CV_32SC1))
using (Mat d = new Mat(corners.size(), CvType.CV_32SC1))
using (Mat dst = new Mat(corners.size(), CvType.CV_32SC2))
{
Core.extractChannel(corners, x, 0);
Core.extractChannel(corners, y, 1);
// the sum of the upper left points is the smallest and the sum of the lower right points is the largest.
Core.add(x, y, d);
Core.MinMaxLocResult result = Core.minMaxLoc(d);
dst.put(0, 0, corners.get((int)result.minLoc.y, 0));
dst.put(2, 0, corners.get((int)result.maxLoc.y, 0));
// the difference in the upper right point is the smallest, and the difference in the lower left is the largest.
Core.subtract(y, x, d);
result = Core.minMaxLoc(d);
dst.put(1, 0, corners.get((int)result.minLoc.y, 0));
dst.put(3, 0, corners.get((int)result.maxLoc.y, 0));
dst.copyTo(corners);
}
return(corners);
}
// Update is called once per frame
void Update()
{
if (webCamTextureToMatHelper.IsPlaying() && webCamTextureToMatHelper.DidUpdateThisFrame())
{
Mat rgbaMat = webCamTextureToMatHelper.GetMat();
// change the color space to YUV.
Imgproc.cvtColor(rgbaMat, yuvMat, Imgproc.COLOR_RGBA2RGB);
Imgproc.cvtColor(yuvMat, yuvMat, Imgproc.COLOR_RGB2YUV);
// grap only the Y component.
Core.extractChannel(yuvMat, yMat, 0);
// blur the image to reduce high frequency noises.
Imgproc.GaussianBlur(yMat, yMat, new Size(3, 3), 0);
// find edges in the image.
Imgproc.Canny(yMat, yMat, 50, 200, 3);
// find contours.
List <MatOfPoint> contours = new List <MatOfPoint>();
Find4PointContours(yMat, contours);
// pick the contour of the largest area and rearrange the points in a consistent order.
MatOfPoint maxAreaContour = GetMaxAreaContour(contours);
maxAreaContour = OrderCornerPoints(maxAreaContour);
bool found = (maxAreaContour.size().area() > 0);
if (found)
{
// trasform the prospective of original image.
using (Mat transformedMat = PerspectiveTransform(rgbaMat, maxAreaContour))
{
outputDisplayAreaMat.setTo(new Scalar(0, 0, 0, 255));
if (transformedMat.width() <= outputDisplayAreaMat.width() && transformedMat.height() <= outputDisplayAreaMat.height() &&
transformedMat.total() >= outputDisplayAreaMat.total() / 16)
{
int x = outputDisplayAreaMat.width() / 2 - transformedMat.width() / 2;
int y = outputDisplayAreaMat.height() / 2 - transformedMat.height() / 2;
using (Mat dstAreaMat = new Mat(outputDisplayAreaMat, new OpenCVForUnity.CoreModule.Rect(x, y, transformedMat.width(), transformedMat.height())))
{
transformedMat.copyTo(dstAreaMat);
}
}
}
}
if (isDebugMode)
{
// draw edge image.
Imgproc.cvtColor(yMat, rgbaMat, Imgproc.COLOR_GRAY2RGBA);
// draw all found conours.
Imgproc.drawContours(rgbaMat, contours, -1, DEBUG_CONTOUR_COLOR, 1);
}
if (found)
{
// draw max area contour.
Imgproc.drawContours(rgbaMat, new List <MatOfPoint> {
maxAreaContour
}, -1, CONTOUR_COLOR, 2);
if (isDebugMode)
{
// draw corner numbers.
for (int i = 0; i < maxAreaContour.toArray().Length; i++)
{
var pt = maxAreaContour.get(i, 0);
Imgproc.putText(rgbaMat, i.ToString(), new Point(pt[0], pt[1]), Imgproc.FONT_HERSHEY_SIMPLEX, 0.5, DEBUG_CORNER_NUMBER_COLOR, 1, Imgproc.LINE_AA, false);
}
}
}
rgbaMat.copyTo(inputDisplayAreaMat);
Utils.fastMatToTexture2D(displayMat, texture, true, 0, true);
}
}