/**
* Reads the bits in the {@link BitMatrix} representing the mapping matrix (No alignment patterns)
* in the correct order in order to reconstitute the codewords bytes contained within the Data
* Matrix Code.
*
* @return bytes encoded within the Data Matrix Code
* @throws FormatException if the exact number of bytes expected is not read
*/
byte[] readCodewords() throws FormatException {
byte[] result = new byte[version.getTotalCodewords()];
int resultOffset = 0;
int row = 4;
int column = 0;
int numRows = mappingBitMatrix.getHeight();
int numColumns = mappingBitMatrix.getWidth();
boolean corner1Read = false;
boolean corner2Read = false;
boolean corner3Read = false;
boolean corner4Read = false;
// Read all of the codewords
do {
// Check the four corner cases
if ((row == numRows) && (column == 0) && !corner1Read) {
result[resultOffset++] = (byte) readCorner1(numRows, numColumns);
row -= 2;
column += 2;
corner1Read = true;
} else if ((row == numRows - 2)
&& (column == 0)
&& ((numColumns & 0x03) != 0)
&& !corner2Read) {
result[resultOffset++] = (byte) readCorner2(numRows, numColumns);
row -= 2;
column += 2;
corner2Read = true;
} else if ((row == numRows + 4)
&& (column == 2)
&& ((numColumns & 0x07) == 0)
&& !corner3Read) {
result[resultOffset++] = (byte) readCorner3(numRows, numColumns);
row -= 2;
column += 2;
corner3Read = true;
} else if ((row == numRows - 2)
&& (column == 0)
&& ((numColumns & 0x07) == 4)
&& !corner4Read) {
result[resultOffset++] = (byte) readCorner4(numRows, numColumns);
row -= 2;
column += 2;
corner4Read = true;
} else {
// Sweep upward diagonally to the right
do {
if ((row < numRows) && (column >= 0) && !readMappingMatrix.get(column, row)) {
result[resultOffset++] = (byte) readUtah(row, column, numRows, numColumns);
}
row -= 2;
column += 2;
} while ((row >= 0) && (column < numColumns));
row += 1;
column += 3;
// Sweep downward diagonally to the left
do {
if ((row >= 0) && (column < numColumns) && !readMappingMatrix.get(column, row)) {
result[resultOffset++] = (byte) readUtah(row, column, numRows, numColumns);
}
row += 2;
column -= 2;
} while ((row < numRows) && (column >= 0));
row += 3;
column += 1;
}
} while ((row < numRows) || (column < numColumns));
if (resultOffset != version.getTotalCodewords()) {
throw FormatException.getFormatInstance();
}
return result;
}
/**
* Creates the version object based on the dimension of the original bit matrix from the
* datamatrix code.
*
* <p>See ISO 16022:2006 Table 7 - ECC 200 symbol attributes
*
* @param bitMatrix Original {@link BitMatrix} including alignment patterns
* @return {@link Version} encapsulating the Data Matrix Code's "version"
* @throws FormatException if the dimensions of the mapping matrix are not valid Data Matrix
* dimensions.
*/
private static Version readVersion(BitMatrix bitMatrix) throws FormatException {
int numRows = bitMatrix.getHeight();
int numColumns = bitMatrix.getWidth();
return Version.getVersionForDimensions(numRows, numColumns);
}