More small changes from code inspection

[zxing.git] / core / src / com / google / zxing / oned / AbstractUPCEANReader.java

diff --git a/core/src/com/google/zxing/oned/AbstractUPCEANReader.java b/core/src/com/google/zxing/oned/AbstractUPCEANReader.java
index e900668..5336e0d 100644 (file)
--- a/core/src/com/google/zxing/oned/AbstractUPCEANReader.java
+++ b/core/src/com/google/zxing/oned/AbstractUPCEANReader.java
@@ -30,12 +30,12 @@ import java.util.Hashtable;
  * of one-dimensional barcodes.</p>
  *
  * @author dswitkin@google.com (Daniel Switkin)
- * @author srowen@google.com (Sean Owen)
+ * @author Sean Owen
  * @author alasdair@google.com (Alasdair Mackintosh)
  */
 public abstract class AbstractUPCEANReader extends AbstractOneDReader implements UPCEANReader {
 
-  private static final int MAX_AVG_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.40625f);
+  private static final int MAX_AVG_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.42f);
   private static final int MAX_INDIVIDUAL_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.7f);
 
   /**
@@ -84,6 +84,12 @@ public abstract class AbstractUPCEANReader extends AbstractOneDReader implements
     }
   }
 
+  private final StringBuffer decodeRowStringBuffer;
+
+  protected AbstractUPCEANReader() {
+    decodeRowStringBuffer = new StringBuffer(20);
+  }
+
   static int[] findStartGuardPattern(BitArray row) throws ReaderException {
     boolean foundStart = false;
     int[] startRange = null;
@@ -92,9 +98,13 @@ public abstract class AbstractUPCEANReader extends AbstractOneDReader implements
       startRange = findGuardPattern(row, nextStart, false, START_END_PATTERN);
       int start = startRange[0];
       nextStart = startRange[1];
-      // As a check, we want to see some white in front of this "start pattern",
-      // maybe as wide as the start pattern itself?
-      foundStart = row.isRange(Math.max(0, start - (3 * (startRange[1] - start)) / 2), start, false);
+      // 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;
   }
@@ -104,19 +114,22 @@ public abstract class AbstractUPCEANReader extends AbstractOneDReader implements
   }
 
   public final Result decodeRow(int rowNumber, BitArray row, int[] startGuardRange) throws ReaderException {
-    StringBuffer result = new StringBuffer(20);
+    StringBuffer result = decodeRowStringBuffer;
+    result.setLength(0);
     int endStart = decodeMiddle(row, startGuardRange, result);
     int[] endRange = decodeEnd(row, endStart);
 
-    // Check for whitespace after the pattern
+    // 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];
-    if (!row.isRange(end, Math.min(row.getSize(), end + (3 * (end - endRange[0])) / 2), false)) {
-      throw new ReaderException("Pattern not followed by whitespace");
+    int quietEnd = end + (end - endRange[0]);
+    if (quietEnd >= row.getSize() || !row.isRange(end, quietEnd, false)) {
+      throw ReaderException.getInstance();
     }
 
     String resultString = result.toString();
     if (!checkChecksum(resultString)) {
-      throw new ReaderException("Checksum failed");
+      throw ReaderException.getInstance();
     }
 
     float left = (float) (startGuardRange[1] + startGuardRange[0]) / 2.0f;
@@ -131,6 +144,13 @@ public abstract class AbstractUPCEANReader extends AbstractOneDReader implements
 
   abstract BarcodeFormat getBarcodeFormat();
 
+  /**
+   * @return {@link #checkStandardUPCEANChecksum(String)} 
+   */
+  boolean checkChecksum(String s) throws ReaderException {
+    return checkStandardUPCEANChecksum(s);
+  }
+
   /**
    * Computes the UPC/EAN checksum on a string of digits, and reports
    * whether the checksum is correct or not.
@@ -139,7 +159,7 @@ public abstract class AbstractUPCEANReader extends AbstractOneDReader implements
    * @return true iff string of digits passes the UPC/EAN checksum algorithm
    * @throws ReaderException if the string does not contain only digits
    */
-  boolean checkChecksum(String s) throws ReaderException {
+  public static boolean checkStandardUPCEANChecksum(String s) throws ReaderException {
     int length = s.length();
     if (length == 0) {
       return false;
@@ -149,7 +169,7 @@ public abstract class AbstractUPCEANReader extends AbstractOneDReader implements
     for (int i = length - 2; i >= 0; i -= 2) {
       int digit = (int) s.charAt(i) - (int) '0';
       if (digit < 0 || digit > 9) {
-        throw new ReaderException("Illegal character during checksum");
+        throw ReaderException.getInstance();
       }
       sum += digit;
     }
@@ -157,7 +177,7 @@ public abstract class AbstractUPCEANReader extends AbstractOneDReader implements
     for (int i = length - 1; i >= 0; i -= 2) {
       int digit = (int) s.charAt(i) - (int) '0';
       if (digit < 0 || digit > 9) {
-        throw new ReaderException("Illegal character during checksum");
+        throw ReaderException.getInstance();
       }
       sum += digit;
     }
@@ -229,7 +249,7 @@ public abstract class AbstractUPCEANReader extends AbstractOneDReader implements
         isWhite = !isWhite;
       }
     }
-    throw new ReaderException("Can't find pattern");
+    throw ReaderException.getInstance();
   }
 
   /**
@@ -261,7 +281,7 @@ public abstract class AbstractUPCEANReader extends AbstractOneDReader implements
     if (bestMatch >= 0) {
       return bestMatch;
     } else {
-      throw new ReaderException("Could not match any digit in pattern");
+      throw ReaderException.getInstance();
     }
   }