Function TraceLine

czxing/src/main/cpp/zxing/src/qrcode/QRDetector.cpp:229–266

}

static RegressionLine TraceLine(const BitMatrix& image, PointF p, PointF d, int edge)
{
	BitMatrixCursorF cur(image, p, d - p);
	RegressionLine line;
	line.setDirectionInward(cur.back());

	// collect points inside the black line -> backup on 3rd edge
	cur.stepToEdge(edge, 0, edge == 3);
	if (edge == 3)
		cur.turnBack();

	auto curI = BitMatrixCursorI(image, PointI(cur.p), PointI(mainDirection(cur.d)));
	// make sure curI positioned such that the white->black edge is directly behind
	// Test image: fix-traceline.jpg
	while (!curI.edgeAtBack()) {
		if (curI.edgeAtLeft())
			curI.turnRight();
		else if (curI.edgeAtRight())
			curI.turnLeft();
		else
			curI.step(-1);
	}

	for (auto dir : {Direction::LEFT, Direction::RIGHT}) {
		auto c = BitMatrixCursorI(image, curI.p, curI.direction(dir));
		auto stepCount = static_cast<int>(maxAbsComponent(cur.p - p));
		do {
			line.add(centered(c.p));
		} while (--stepCount > 0 && c.stepAlongEdge(dir, true));
	}

	line.evaluate(1.0, true);

	for (auto p : line.points())
		log(p, 2);

	return line;
}

// estimate how tilted the symbol is (return value between 1 and 2, see also above)
static double EstimateTilt(const FinderPatternSet& fp)