public void run() {
ArrayList<Geometry.Quad> squares;
Mat image = new Mat();
Utils.bitmapToMat(source, image);
Mat bwimage = new Mat();
cvtColor(image, bwimage, COLOR_RGB2GRAY);
Mat blurred = new Mat();
medianBlur(image, blurred, 9);
int width = blurred.width();
int height = blurred.height();
int depth = blurred.depth();
Mat gray0 = new Mat(width, height, depth);
blurred.copyTo(gray0);
squares = new ArrayList<Geometry.Quad>();
// find squares in every color plane of the image
for (int c = 0; c < 3; c++) {
Core.mixChannels(
Arrays.asList(blurred), Arrays.asList(new Mat[] {gray0}), new MatOfInt(c, 0));
// try several threshold levels
int thresholdLevel = 8;
for (int l = 0; l < thresholdLevel; l++) {
// use canny instead of 0 threshold level
// canny helps catch squares with gradient shading
Mat gray = new Mat();
if (l == 0) {
Canny(gray0, gray, 10.0, 20.0, 3, false);
Mat kernel = new Mat(11, 11, CvType.CV_8UC1, new Scalar(1));
dilate(gray, gray, kernel);
} else {
Mat thresh = new Mat(gray0.rows(), gray0.cols(), gray0.type());
threshold(gray0, thresh, ((double) l) / thresholdLevel * 255, 128, THRESH_BINARY_INV);
cvtColor(thresh, gray, COLOR_BGR2GRAY);
}
// find contours and store them in a list
List<MatOfPoint> contours = new ArrayList<MatOfPoint>();
findContours(gray, contours, new Mat(), RETR_LIST, CHAIN_APPROX_SIMPLE);
// test contours
for (MatOfPoint contour : contours) {
// approximate contour with accuracy proportional to the contour perimeter
MatOfPoint2f thisContour = new MatOfPoint2f(contour.toArray());
double arclength = 0.02 * arcLength(thisContour, true);
MatOfPoint2f approx = new MatOfPoint2f();
approxPolyDP(thisContour, approx, arclength, true);
double area = contourArea(approx);
boolean isConvex = isContourConvex(new MatOfPoint(approx.toArray()));
if (approx.rows() == 4 && Math.abs(area) > SQUARE_SIZE && isConvex) {
double maxCosine = 0;
Point[] approxArray = approx.toArray();
for (int j = 2; j < 5; j++) {
double cosine =
Math.abs(angle(approxArray[j % 4], approxArray[j - 2], approxArray[j - 1]));
maxCosine = Math.max(maxCosine, cosine);
}
if (maxCosine > THRESHOLD_COS) {
squares.add(new Geometry.Quad(approxArray));
Log.d(TAG, "area = " + area);
}
}
}
}
}
result = new Bundle();
result.putParcelableArrayList("squares", squares);
Log.d(TAG, "result created");
finish();
}
