private static bool TryFindStartingAngleAndSegmentSize(TagImage tagImage)
{
double startingAngle = -1;
const double angleStepSize = Math.PI / 360.0 / 2.0;
const int radiusOffset = 2;
double currentAngle = 0.0;
for (int step = 0; currentAngle < Math.PI * 2; step++)
{
currentAngle = angleStepSize * step;
CalculateCoords(tagImage, currentAngle, tagImage.CodeRadius + radiusOffset, out int x, out int y);
_debugImage?.WriteColor(x, y, 0xff0000ff);
if (x < 0 || y < 0 || x > tagImage.Width || y > tagImage.Width)
{
continue;
}
bool hasPixel = tagImage.CheckPixel(x, y);
// Find the first pixel in the notch of the first layer
if (startingAngle < 0 && !hasPixel)
{
startingAngle = currentAngle - angleStepSize;
_debugImage?.WriteColor(x, y, 0xffff00ff);
}
// Find the last pixel in the notch of the first layer
if (startingAngle > 0 && hasPixel)
{
tagImage.CodeStartingAngle = startingAngle;
tagImage.CodeSegmentSize = currentAngle - startingAngle;
_debugImage?.WriteColor(x, y, 0xff00ffff);
return(true);
}
}
return(false);
}
private static bool TryCalculateDistances(TagImage tagImage, int originX, int originY, out int left, out int right, out int down, out int up)
{
left = -1;
right = -1;
down = -1;
up = -1;
int size = tagImage.Width / 2;
uint diff = 0;
for (int i = 1; i < size; i++)
{
int x = originX - i;
int y = originY;
if (x >= 0 && x < tagImage.Width)
{
if (left < 0 && tagImage.CheckPixel(x, y, out diff))
{
left = x + 1;
}
_debugImage?.WriteColor(x, y, diff | 0xff000000);
}
x = originX + i;
if (x >= 0 && x < tagImage.Width)
{
if (right < 0 && tagImage.CheckPixel(x, y, out diff))
{
right = x - 1;
}
_debugImage?.WriteColor(x, y, diff | 0xff000000);
}
x = originX;
y = originY - i;
if (y >= 0 && y < tagImage.Height)
{
if (down < 0 && tagImage.CheckPixel(x, y, out diff))
{
down = y + 1;
}
_debugImage?.WriteColor(x, y, diff | 0xff000000);
}
y = originY + i;
if (y >= 0 && y < tagImage.Height)
{
if (up < 0 && tagImage.CheckPixel(x, y, out diff))
{
up = y - 1;
}
_debugImage?.WriteColor(x, y, diff | 0xff000000);
}
if (left >= 0 && right >= 0 && down >= 0 && up >= 0)
{
return(true);
}
}
return(false);
}
private static bool TryReadData(TagImage tagImage, out byte[] bytes)
{
bytes = null;
int segments = CalculateSegmentCount(tagImage.CodeSegmentSize);
if (segments <= 0)
{
return(false);
}
double halfSegment = tagImage.CodeSegmentSize / 2.0;
int byteIndex = 0;
byte currentBit = 1;
byte currentByte = 0;
byte sizeByte = 0;
for (int layer = 0; layer < tagImage.CodeLayerCount; layer++)
{
for (int segment = 1; segment < segments; segment++)
{
// Calculate coordinates
double angle = tagImage.CodeStartingAngle + segment * tagImage.CodeSegmentSize + halfSegment;
int distance = tagImage.CodeRadius + tagImage.CodeLayerSize + layer * tagImage.CodeLayerSize + tagImage.CodeLayerSize / 2;
CalculateCoords(tagImage, angle, distance, out int x, out int y);
// Read bit
if (tagImage.CheckPixel(x, y))
{
currentByte |= currentBit;
}
// Advance bit and check if there are more bits
currentBit <<= 1;
if (currentBit > 0)
{
continue;
}
// No more bits, handle byte
currentBit = 1;
if (sizeByte == 0)
{
// Size not read yet, use the current byte value as data size and continue reading
sizeByte = currentByte;
currentByte = 0;
bytes = new byte[sizeByte];
continue;
}
if (byteIndex == sizeByte)
{
// We have read all bytes, check hash byte and return
byte hash = CalculateHash(bytes);
return(hash == currentByte);
}
// Push the current byte to the byte array and continue reading
bytes[byteIndex] = currentByte;
currentByte = 0;
byteIndex++;
}
}
return(false);
}
