zxing/csharp/oned/UPCEANReader.cs
srowen d4efd44fb0 New C# port from Suraj Supekar
git-svn-id: https://zxing.googlecode.com/svn/trunk@1202 59b500cc-1b3d-0410-9834-0bbf25fbcc57
2010-02-05 19:52:53 +00:00

359 lines
14 KiB
C#
Executable file

/*
* Copyright 2008 ZXing authors
*
* 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.
*/
using System;
using ReaderException = com.google.zxing.ReaderException;
using Result = com.google.zxing.Result;
using ResultPointCallback = com.google.zxing.ResultPointCallback;
using DecodeHintType = com.google.zxing.DecodeHintType;
using ResultPoint = com.google.zxing.ResultPoint;
using BarcodeFormat = com.google.zxing.BarcodeFormat;
using BitArray = com.google.zxing.common.BitArray;
namespace com.google.zxing.oned
{
/// <summary> <p>Encapsulates functionality and implementation that is common to UPC and EAN families
/// of one-dimensional barcodes.</p>
///
/// </summary>
/// <author> dswitkin@google.com (Daniel Switkin)
/// </author>
/// <author> Sean Owen
/// </author>
/// <author> alasdair@google.com (Alasdair Mackintosh)
/// </author>
/// <author>www.Redivivus.in (suraj.supekar@redivivus.in) - Ported from ZXING Java Source
/// </author>
public abstract class UPCEANReader:OneDReader
{
/// <summary> Get the format of this decoder.
///
/// </summary>
/// <returns> The 1D format.
/// </returns>
internal abstract BarcodeFormat BarcodeFormat{get;}
// These two values are critical for determining how permissive the decoding will be.
// We've arrived at these values through a lot of trial and error. Setting them any higher
// lets false positives creep in quickly.
//UPGRADE_NOTE: Final was removed from the declaration of 'MAX_AVG_VARIANCE '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
//UPGRADE_WARNING: Data types in Visual C# might be different. Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
private static readonly int MAX_AVG_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.42f);
//UPGRADE_NOTE: Final was removed from the declaration of 'MAX_INDIVIDUAL_VARIANCE '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
//UPGRADE_WARNING: Data types in Visual C# might be different. Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
private static readonly int MAX_INDIVIDUAL_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.7f);
/// <summary> Start/end guard pattern.</summary>
//UPGRADE_NOTE: Final was removed from the declaration of 'START_END_PATTERN'. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
internal static readonly int[] START_END_PATTERN = new int[]{1, 1, 1};
/// <summary> Pattern marking the middle of a UPC/EAN pattern, separating the two halves.</summary>
//UPGRADE_NOTE: Final was removed from the declaration of 'MIDDLE_PATTERN'. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
internal static readonly int[] MIDDLE_PATTERN = new int[]{1, 1, 1, 1, 1};
/// <summary> "Odd", or "L" patterns used to encode UPC/EAN digits.</summary>
//UPGRADE_NOTE: Final was removed from the declaration of 'L_PATTERNS'. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
internal static readonly int[][] L_PATTERNS = new int[][]{new int[]{3, 2, 1, 1}, new int[]{2, 2, 2, 1}, new int[]{2, 1, 2, 2}, new int[]{1, 4, 1, 1}, new int[]{1, 1, 3, 2}, new int[]{1, 2, 3, 1}, new int[]{1, 1, 1, 4}, new int[]{1, 3, 1, 2}, new int[]{1, 2, 1, 3}, new int[]{3, 1, 1, 2}};
/// <summary> As above but also including the "even", or "G" patterns used to encode UPC/EAN digits.</summary>
internal static int[][] L_AND_G_PATTERNS;
//UPGRADE_NOTE: Final was removed from the declaration of 'decodeRowStringBuffer '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
private System.Text.StringBuilder decodeRowStringBuffer;
protected internal UPCEANReader()
{
decodeRowStringBuffer = new System.Text.StringBuilder(20);
}
internal static int[] findStartGuardPattern(BitArray row)
{
bool foundStart = false;
int[] startRange = null;
int nextStart = 0;
while (!foundStart)
{
startRange = findGuardPattern(row, nextStart, false, START_END_PATTERN);
int start = startRange[0];
nextStart = startRange[1];
// Make sure there is a quiet zone at least as big as the start pattern before the barcode.
// If this check would run off the left edge of the image, do not accept this barcode,
// as it is very likely to be a false positive.
int quietStart = start - (nextStart - start);
if (quietStart >= 0)
{
foundStart = row.isRange(quietStart, start, false);
}
}
return startRange;
}
public override Result decodeRow(int rowNumber, BitArray row, System.Collections.Hashtable hints)
{
return decodeRow(rowNumber, row, findStartGuardPattern(row), hints);
}
/// <summary> <p>Like {@link #decodeRow(int, BitArray, java.util.Hashtable)}, but
/// allows caller to inform method about where the UPC/EAN start pattern is
/// found. This allows this to be computed once and reused across many implementations.</p>
/// </summary>
public virtual Result decodeRow(int rowNumber, BitArray row, int[] startGuardRange, System.Collections.Hashtable hints)
{
ResultPointCallback resultPointCallback = hints == null?null:(ResultPointCallback) hints[DecodeHintType.NEED_RESULT_POINT_CALLBACK];
if (resultPointCallback != null)
{
resultPointCallback.foundPossibleResultPoint(new ResultPoint((startGuardRange[0] + startGuardRange[1]) / 2.0f, rowNumber));
}
System.Text.StringBuilder result = decodeRowStringBuffer;
result.Length = 0;
int endStart = decodeMiddle(row, startGuardRange, result);
if (resultPointCallback != null)
{
resultPointCallback.foundPossibleResultPoint(new ResultPoint(endStart, rowNumber));
}
int[] endRange = decodeEnd(row, endStart);
if (resultPointCallback != null)
{
resultPointCallback.foundPossibleResultPoint(new ResultPoint((endRange[0] + endRange[1]) / 2.0f, rowNumber));
}
// Make sure there is a quiet zone at least as big as the end pattern after the barcode. The
// spec might want more whitespace, but in practice this is the maximum we can count on.
int end = endRange[1];
int quietEnd = end + (end - endRange[0]);
if (quietEnd >= row.Size || !row.isRange(end, quietEnd, false))
{
throw ReaderException.Instance;
}
System.String resultString = result.ToString();
if (!checkChecksum(resultString))
{
throw ReaderException.Instance;
}
//UPGRADE_WARNING: Data types in Visual C# might be different. Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
float left = (float) (startGuardRange[1] + startGuardRange[0]) / 2.0f;
//UPGRADE_WARNING: Data types in Visual C# might be different. Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
float right = (float) (endRange[1] + endRange[0]) / 2.0f;
//UPGRADE_WARNING: Data types in Visual C# might be different. Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
return new Result(resultString, null, new ResultPoint[]{new ResultPoint(left, (float) rowNumber), new ResultPoint(right, (float) rowNumber)}, BarcodeFormat);
}
/// <returns> {@link #checkStandardUPCEANChecksum(String)}
/// </returns>
//UPGRADE_NOTE: Access modifiers of method 'checkChecksum' were changed to 'protected'. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1204'"
protected internal virtual bool checkChecksum(System.String s)
{
return checkStandardUPCEANChecksum(s);
}
/// <summary> Computes the UPC/EAN checksum on a string of digits, and reports
/// whether the checksum is correct or not.
///
/// </summary>
/// <param name="s">string of digits to check
/// </param>
/// <returns> true iff string of digits passes the UPC/EAN checksum algorithm
/// </returns>
/// <throws> ReaderException if the string does not contain only digits </throws>
private static bool checkStandardUPCEANChecksum(System.String s)
{
int length = s.Length;
if (length == 0)
{
return false;
}
int sum = 0;
for (int i = length - 2; i >= 0; i -= 2)
{
int digit = (int) s[i] - (int) '0';
if (digit < 0 || digit > 9)
{
throw ReaderException.Instance;
}
sum += digit;
}
sum *= 3;
for (int i = length - 1; i >= 0; i -= 2)
{
int digit = (int) s[i] - (int) '0';
if (digit < 0 || digit > 9)
{
throw ReaderException.Instance;
}
sum += digit;
}
return sum % 10 == 0;
}
//UPGRADE_NOTE: Access modifiers of method 'decodeEnd' were changed to 'protected'. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1204'"
protected internal virtual int[] decodeEnd(BitArray row, int endStart)
{
return findGuardPattern(row, endStart, false, START_END_PATTERN);
}
/// <param name="row">row of black/white values to search
/// </param>
/// <param name="rowOffset">position to start search
/// </param>
/// <param name="whiteFirst">if true, indicates that the pattern specifies white/black/white/...
/// pixel counts, otherwise, it is interpreted as black/white/black/...
/// </param>
/// <param name="pattern">pattern of counts of number of black and white pixels that are being
/// searched for as a pattern
/// </param>
/// <returns> start/end horizontal offset of guard pattern, as an array of two ints
/// </returns>
/// <throws> ReaderException if pattern is not found </throws>
internal static int[] findGuardPattern(BitArray row, int rowOffset, bool whiteFirst, int[] pattern)
{
int patternLength = pattern.Length;
int[] counters = new int[patternLength];
int width = row.Size;
bool isWhite = false;
while (rowOffset < width)
{
isWhite = !row.get_Renamed(rowOffset);
if (whiteFirst == isWhite)
{
break;
}
rowOffset++;
}
int counterPosition = 0;
int patternStart = rowOffset;
for (int x = rowOffset; x < width; x++)
{
bool pixel = row.get_Renamed(x);
if (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 ReaderException.Instance;
}
/// <summary> Attempts to decode a single UPC/EAN-encoded digit.
///
/// </summary>
/// <param name="row">row of black/white values to decode
/// </param>
/// <param name="counters">the counts of runs of observed black/white/black/... values
/// </param>
/// <param name="rowOffset">horizontal offset to start decoding from
/// </param>
/// <param name="patterns">the set of patterns to use to decode -- sometimes different encodings
/// for the digits 0-9 are used, and this indicates the encodings for 0 to 9 that should
/// be used
/// </param>
/// <returns> horizontal offset of first pixel beyond the decoded digit
/// </returns>
/// <throws> ReaderException if digit cannot be decoded </throws>
internal static int decodeDigit(BitArray row, int[] counters, int rowOffset, int[][] patterns)
{
recordPattern(row, rowOffset, 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 ReaderException.Instance;
}
}
/// <summary> Subclasses override this to decode the portion of a barcode between the start
/// and end guard patterns.
///
/// </summary>
/// <param name="row">row of black/white values to search
/// </param>
/// <param name="startRange">start/end offset of start guard pattern
/// </param>
/// <param name="resultString">{@link StringBuffer} to append decoded chars to
/// </param>
/// <returns> horizontal offset of first pixel after the "middle" that was decoded
/// </returns>
/// <throws> ReaderException if decoding could not complete successfully </throws>
protected internal abstract int decodeMiddle(BitArray row, int[] startRange, System.Text.StringBuilder resultString);
static UPCEANReader()
{
{
L_AND_G_PATTERNS = new int[20][];
for (int i = 0; i < 10; i++)
{
L_AND_G_PATTERNS[i] = L_PATTERNS[i];
}
for (int i = 10; i < 20; i++)
{
int[] widths = L_PATTERNS[i - 10];
int[] reversedWidths = new int[widths.Length];
for (int j = 0; j < widths.Length; j++)
{
reversedWidths[j] = widths[widths.Length - j - 1];
}
L_AND_G_PATTERNS[i] = reversedWidths;
}
}
}
}
}