/**
* Determines the symbol's unit length by counting the number of pixels between the outer edges of
* the first black ring. North, south, east, and west readings are taken and the average is
* returned.
*/
protected float readUnit(Scanner scanner) {
int sx = (int) Math.round(x);
int sy = (int) Math.round(y);
int iwidth = scanner.getImageWidth();
int iheight = scanner.getImageHeight();
boolean whiteL = true;
boolean whiteR = true;
boolean whiteU = true;
boolean whiteD = true;
int sample;
int distL = 0, distR = 0, distU = 0, distD = 0;
for (int i = 1; true; i++) {
if (sx - i < 1 || sx + i >= iwidth - 1 || sy - i < 1 || sy + i >= iheight - 1 || i > 100) {
return -1;
}
// Left sample
sample = scanner.getBW3x3(sx - i, sy);
if (distL <= 0) {
if (whiteL && sample == 0) {
whiteL = false;
} else if (!whiteL && sample == 1) {
distL = i;
}
}
// Right sample
sample = scanner.getBW3x3(sx + i, sy);
if (distR <= 0) {
if (whiteR && sample == 0) {
whiteR = false;
} else if (!whiteR && sample == 1) {
distR = i;
}
}
// Up sample
sample = scanner.getBW3x3(sx, sy - i);
if (distU <= 0) {
if (whiteU && sample == 0) {
whiteU = false;
} else if (!whiteU && sample == 1) {
distU = i;
}
}
// Down sample
sample = scanner.getBW3x3(sx, sy + i);
if (distD <= 0) {
if (whiteD && sample == 0) {
whiteD = false;
} else if (!whiteD && sample == 1) {
distD = i;
}
}
if (distR > 0 && distL > 0 && distU > 0 && distD > 0) {
float u = (distR + distL + distU + distD) / 8.0f;
if (Math.abs(distR + distL - distU - distD) > u) {
return -1;
} else {
return u;
}
}
}
}
