// Adapted from "sizeOfBlackWhiteBlackRun" in zxing::qrcode::Detector
Point QREdgeDetector::endOfReverseBlackWhiteBlackRun(const BitMatrix& image, Point from, Point to) {
int fromX = (int)from.x;
int fromY = (int)from.y;
int toX = (int)to.x;
int toY = (int)to.y;
bool steep = abs(toY - fromY) > abs(toX - fromX);
if (steep) {
int temp = fromX;
fromX = fromY;
fromY = temp;
temp = toX;
toX = toY;
toY = temp;
}
int dx = abs(toX - fromX);
int dy = abs(toY - fromY);
int error = -dx >> 1;
int ystep = fromY < toY ? -1 : 1;
int xstep = fromX < toX ? -1 : 1;
int state = 0; // In black pixels, looking for white, first or second time
// In case there are no points, prepopulate to from
int realX = fromX;
int realY = fromY;
for (int x = fromX, y = fromY; x != toX; x += xstep) {
realX = steep ? y : x;
realY = steep ? x : y;
if(realX < 0 || realY < 0 || realX >= (int)image.getWidth() || realY >= (int)image.getHeight())
break;
if (state == 1) { // In white pixels, looking for black
if (image.get(realX, realY)) {
state++;
}
} else {
if (!image.get(realX, realY)) {
state++;
}
}
if (state == 3) { // Found black, white, black, and stumbled back onto white; done
return Point(realX, realY);
}
error += dy;
if (error > 0) {
y += ystep;
error -= dx;
}
}
// B-W-B run not found, return the last point visited.
return Point(realX, realY);
}
void findEdgePoints(std::vector<Point>& points, const BitMatrix& image, Point start, Point end, bool invert, int skip, float deviation) {
float xdist = end.x - start.x;
float ydist = end.y - start.y;
float length = sqrt(xdist * xdist + ydist * ydist);
int var;
if (abs(xdist) > abs(ydist)) {
// Horizontal
if (xdist < 0)
skip = -skip;
var = int(abs(deviation * length / xdist));
float dy = ydist / xdist * skip;
bool left = (skip < 0) ^ invert;
int x = int(start.x);
int steps = int(xdist / skip);
for (int i = 0; i < steps; i++) {
x += skip;
if (x < 0 || x >= (int)image.getWidth())
continue; // In case we start off the edge
int my = int(start.y + dy * i);
int ey = min(my + var + 1, (int)image.getHeight() - 1);
int sy = max(my - var, 0);
for (int y = sy + 1; y < ey; y++) {
if (left) {
if (image.get(x, y) && !image.get(x, y + 1)) {
points.push_back(Point(x, y + 0.5f));
}
} else {
if (!image.get(x, y) && image.get(x, y + 1)) {
points.push_back(Point(x, y + 0.5f));
}
}
}
}
} else {
// Vertical
if (ydist < 0)
skip = -skip;
var = int(abs(deviation * length / ydist));
float dx = xdist / ydist * skip;
bool down = (skip > 0) ^ invert;
int y = int(start.y);
int steps = int(ydist / skip);
for (int i = 0; i < steps; i++) {
y += skip;
if (y < 0 || y >= (int)image.getHeight())
continue; // In case we start off the edge
int mx = int(start.x + dx * i);
int ex = min(mx + var + 1, (int)image.getWidth() - 1);
int sx = max(mx - var, 0);
for (int x = sx + 1; x < ex; x++) {
if (down) {
if (image.get(x, y) && !image.get(x + 1, y)) {
points.push_back(Point(x + 0.5f, y));
}
} else {
if (!image.get(x, y) && image.get(x + 1, y)) {
points.push_back(Point(x + 0.5f, y));
}
}
}
}
}
}