/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
namespace com.google.zxing.oned
{
/**
* <p>Implements decoding of the EAN-13 format.</p>
*
* @author dswitkin@google.com (Daniel Switkin)
* @author Sean Owen
* @author alasdair@google.com (Alasdair Mackintosh)
*/
using System.Text;
using com.google.zxing.common;
public sealed class ITFReader : AbstractOneDReader
{
private static int MAX_AVG_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.42f);
private static int MAX_INDIVIDUAL_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.8f);
private static int W = 3; // Pixel width of a wide line
private static int N = 1; // Pixed width of a narrow line
// Stores the actual narrow line width of the image being decoded.
private int narrowLineWidth = -1;
/**
* Start/end guard pattern.
*
* Note: The end pattern is reversed because the row is reversed before
* searching for the END_PATTERN
*/
private static int[] START_PATTERN = {N, N, N, N};
private static int[] END_PATTERN_REVERSED = {N, N, W};
/**
* Patterns of Wide / Narrow lines to indicate each digit
*/
private static int[][] PATTERNS = new int[][]{
new int[]{N, N, W, W, N}, // 0
new int[]{W, N, N, N, W}, // 1
new int[]{N, W, N, N, W}, // 2
new int[]{W, W, N, N, N}, // 3
new int[]{N, N, W, N, W}, // 4
new int[]{W, N, W, N, N}, // 5
new int[]{N, W, W, N, N}, // 6
new int[]{N, N, N, W, W}, // 7
new int[]{W, N, N, W, N}, // 8
new int[]{N, W, N, W, N} // 9
};
public override Result decodeRow(int rowNumber, BitArray row, System.Collections.Hashtable hints) {
StringBuilder result = new StringBuilder(20);
// Find out where the Middle section (payload) starts & ends
int[] startRange = decodeStart(row);
int[] endRange = decodeEnd(row);
decodeMiddle(row, startRange[1], endRange[0], result);
string resultString = result.ToString();
// To avoid false positives with 2D barcodes (and other patterns), make
// an assumption that the decoded string must be 6, 10 or 14 digits.
int length = resultString.Length;
if (length != 6 && length != 10 && length != 14) {
throw new ReaderException();
}
return new Result(
resultString,
null, // no natural byte representation for these barcodes
new ResultPoint[] { new GenericResultPoint(startRange[1], (float) rowNumber),
new GenericResultPoint(startRange[0], (float) rowNumber)},
BarcodeFormat.ITF);
}
/**
* @param row row of black/white values to search
* @param payloadStart offset of start pattern
* @param resultString {@link StringBuilder} to Append decoded chars to
* @throws ReaderException if decoding could not complete successfully
*/
static void decodeMiddle(BitArray row, int payloadStart, int payloadEnd, StringBuilder resultString) {
// Digits are interleaved in pairs - 5 black lines for one digit, and the
// 5
// interleaved white lines for the second digit.
// Therefore, need to scan 10 lines and then
// split these into two arrays
int[] counterDigitPair = new int[10];
int[] counterBlack = new int[5];
int[] counterWhite = new int[5];
while (payloadStart < payloadEnd) {
// Get 10 runs of black/white.
recordPattern(row, payloadStart, counterDigitPair);
// Split them into each array
for (int k = 0; k < 5; k++) {
int twoK = k << 1;
counterBlack[k] = counterDigitPair[twoK];
counterWhite[k] = counterDigitPair[twoK + 1];
}
int bestMatch = decodeDigit(counterBlack);
resultString.Append((char) ('0' + bestMatch));
bestMatch = decodeDigit(counterWhite);
resultString.Append((char) ('0' + bestMatch));
for (int i = 0; i < counterDigitPair.Length; i++) {
payloadStart += counterDigitPair[i];
}
}
}
/**
* Identify where the start of the middle / payload section starts.
*
* @param row row of black/white values to search
* @return Array, containing index of start of 'start block' and end of
* 'start block'
* @throws ReaderException
*/
int[] decodeStart(BitArray row) {
int endStart = skipWhiteSpace(row);
int[] startPattern = findGuardPattern(row, endStart, START_PATTERN);
// Determine the width of a narrow line in pixels. We can do this by
// getting the width of the start pattern and dividing by 4 because its
// made up of 4 narrow lines.
this.narrowLineWidth = (startPattern[1] - startPattern[0]) >> 2;
validateQuietZone(row, startPattern[0]);
return startPattern;
}
/**
* The start & end patterns must be pre/post fixed by a quiet zone. This
* zone must be at least 10 times the width of a narrow line. Scan back until
* we either get to the start of the barcode or match the necessary number of
* quiet zone pixels.
*
* Note: Its assumed the row is reversed when using this method to find
* quiet zone after the end pattern.
*
* ref: http://www.barcode-1.net/i25code.html
*
* @param row bit array representing the scanned barcode.
* @param startPattern index into row of the start or end pattern.
* @throws ReaderException if the quiet zone cannot be found, a ReaderException is thrown.
*/
private void validateQuietZone(BitArray row, int startPattern) {
int quietCount = this.narrowLineWidth * 10; // expect to find this many pixels of quiet zone
for (int i = startPattern - 1; quietCount > 0 && i >= 0; i--) {
if (row.get(i)) {
break;
}
quietCount--;
}
if (quietCount != 0) {
// Unable to find the necessary number of quiet zone pixels.
throw new ReaderException();
}
}
/**
* Skip all whitespace until we get to the first black line.
*
* @param row row of black/white values to search
* @return index of the first black line.
* @throws ReaderException Throws exception if no black lines are found in the row
*/
private int skipWhiteSpace(BitArray row) {
int width = row.getSize();
int endStart = 0;
while (endStart < width) {
if (row.get(endStart)) {
break;
}
endStart++;
}
if (endStart == width) {
throw new ReaderException();
}
return endStart;
}
/**
* Identify where the end of the middle / payload section ends.
*
* @param row row of black/white values to search
* @return Array, containing index of start of 'end block' and end of 'end
* block'
* @throws ReaderException
*/
int[] decodeEnd(BitArray row) {
// For convenience, reverse the row and then
// search from 'the start' for the end block
row.reverse();
int endStart = skipWhiteSpace(row);
int[] endPattern;
try {
endPattern = findGuardPattern(row, endStart, END_PATTERN_REVERSED);
} catch (ReaderException e) {
// Put our row of data back the right way before throwing
row.reverse();
throw e;
}
// The start & end patterns must be pre/post fixed by a quiet zone. This
// zone must be at least 10 times the width of a narrow line.
// ref: http://www.barcode-1.net/i25code.html
validateQuietZone(row, endPattern[0]);
// Now recalc the indicies of where the 'endblock' starts & stops to
// accomodate
// the reversed nature of the search
int temp = endPattern[0];
endPattern[0] = row.getSize() - endPattern[1];
endPattern[1] = row.getSize() - temp;
// Put the row back the righ way.
row.reverse();
return endPattern;
}
/**
* @param row row of black/white values to search
* @param rowOffset position to start search
* @param pattern pattern of counts of number of black and white pixels that are
* being searched for as a pattern
* @return start/end horizontal offset of guard pattern, as an array of two
* ints
* @throws ReaderException if pattern is not found
*/
int[] findGuardPattern(BitArray row, int rowOffset, int[] pattern) {
// TODO: This is very similar to implementation in AbstractUPCEANReader. Consider if they can be merged to
// a single method.
int patternLength = pattern.Length;
int[] counters = new int[patternLength];
int width = row.getSize();
bool isWhite = false;
int counterPosition = 0;
int patternStart = rowOffset;
for (int x = rowOffset; x < width; x++) {
bool pixel = row.get(x);
if ((!pixel && isWhite) || (pixel && !isWhite)) {
counters[counterPosition]++;
} else {
if (counterPosition == patternLength - 1) {
if (patternMatchVariance(counters, pattern, MAX_INDIVIDUAL_VARIANCE) < MAX_AVG_VARIANCE) {
return new int[]{patternStart, x};
}
patternStart += counters[0] + counters[1];
for (int y = 2; y < patternLength; y++) {
counters[y - 2] = counters[y];
}
counters[patternLength - 2] = 0;
counters[patternLength - 1] = 0;
counterPosition--;
} else {
counterPosition++;
}
counters[counterPosition] = 1;
isWhite = !isWhite;
}
}
throw new ReaderException();
}
/**
* Attempts to decode a sequence of ITF black/white lines into single
* digit.
*
* @param counters the counts of runs of observed black/white/black/... values
* @return The decoded digit
* @throws ReaderException if digit cannot be decoded
*/
private static int decodeDigit(int[] counters) {
int bestVariance = MAX_AVG_VARIANCE; // worst variance we'll accept
int bestMatch = -1;
int max = PATTERNS.Length;
for (int i = 0; i < max; i++) {
int[] pattern = PATTERNS[i];
int variance = patternMatchVariance(counters, pattern, MAX_INDIVIDUAL_VARIANCE);
if (variance < bestVariance) {
bestVariance = variance;
bestMatch = i;
}
}
if (bestMatch >= 0) {
return bestMatch;
} else {
throw new ReaderException();
}
}
}
}