Overhaul 'extractPureBits' implementations and standardize. Improve by looking for bottom-right black pixel. Fix PDF417 pure barcode mode along the way.

git-svn-id: https://zxing.googlecode.com/svn/trunk@1628 59b500cc-1b3d-0410-9834-0bbf25fbcc57

core/src/com/google/zxing/common/BitMatrix.java

@@ -170,6 +170,28 @@ public final class BitMatrix {
     return new int[] {x, y};
   }
 
+  public int[] getBottomRightOnBit() {
+    int bitsOffset = bits.length - 1;
+    while (bitsOffset >= 0 && bits[bitsOffset] == 0) {
+      bitsOffset--;
+    }
+    if (bitsOffset < 0) {
+      return null;
+    }
+
+    int y = bitsOffset / rowSize;
+    int x = (bitsOffset % rowSize) << 5;
+
+    int theBits = bits[bitsOffset];
+    int bit = 31;
+    while ((theBits >>> bit) == 0) {
+      bit--;
+    }
+    x += bit;
+
+    return new int[] {x, y};
+  }
+
   /**
    * @return The width of the matrix
    */

core/src/com/google/zxing/datamatrix/DataMatrixReader.java

@@ -86,76 +86,71 @@ public final class DataMatrixReader implements Reader {
   }
 
   /**
-   * This method detects a Data Matrix code in a "pure" image -- that is, pure monochrome image
-   * which contains only an unrotated, unskewed, image of a Data Matrix code, with some white border
+   * This method detects a code in a "pure" image -- that is, pure monochrome image
+   * which contains only an unrotated, unskewed, image of a code, with some white border
    * around it. This is a specialized method that works exceptionally fast in this special
    * case.
    *
+   * @see com.google.zxing.pdf417.PDF417Reader#extractPureBits(BitMatrix)
    * @see com.google.zxing.qrcode.QRCodeReader#extractPureBits(BitMatrix)
    */
   private static BitMatrix extractPureBits(BitMatrix image) throws NotFoundException {
 
-    int height = image.getHeight();
-    int width = image.getWidth();
-    int minDimension = Math.min(height, width);
-
-    // And then keep tracking across the top-left black module to determine module size
-    //int moduleEnd = borderWidth;
     int[] leftTopBlack = image.getTopLeftOnBit();
-    if (leftTopBlack == null) {
-      throw NotFoundException.getNotFoundInstance();
-    }
-    int x = leftTopBlack[0];
-    int y = leftTopBlack[1];
-    while (x < minDimension && y < minDimension && image.get(x, y)) {
-      x++;
-    }
-    if (x == minDimension) {
+    int[] rightBottomBlack = image.getBottomRightOnBit();
+    if (leftTopBlack == null || rightBottomBlack == null) {
       throw NotFoundException.getNotFoundInstance();
     }
 
-    int moduleSize = x - leftTopBlack[0];
+    int moduleSize = moduleSize(leftTopBlack, image);
 
-    // And now find where the rightmost black module on the first row ends
-    int rowEndOfSymbol = width - 1;
-    while (rowEndOfSymbol >= 0 && !image.get(rowEndOfSymbol, y)) {
-      rowEndOfSymbol--;
-    }
-    if (rowEndOfSymbol < 0) {
+    int top = leftTopBlack[1];
+    int bottom = rightBottomBlack[1];
+    int left = leftTopBlack[0];
+    int right = rightBottomBlack[0];
+
+    int matrixWidth = (right - left + 1) / moduleSize;
+    int matrixHeight = (bottom - top + 1) / moduleSize;
+    if (matrixWidth == 0 || matrixHeight == 0) {
       throw NotFoundException.getNotFoundInstance();
     }
-    rowEndOfSymbol++;
-
-    // Make sure width of barcode is a multiple of module size
-    if ((rowEndOfSymbol - x) % moduleSize != 0) {
-      throw NotFoundException.getNotFoundInstance();
-    }
-    int dimension = 2 + ((rowEndOfSymbol - x) / moduleSize);
-
-    y += moduleSize;
 
     // Push in the "border" by half the module width so that we start
     // sampling in the middle of the module. Just in case the image is a
     // little off, this will help recover.
-    x -= moduleSize >> 1;
-    y -= moduleSize >> 1;
-
-    if ((x + (dimension - 1) * moduleSize) >= width ||
-        (y + (dimension - 1) * moduleSize) >= height) {
-      throw NotFoundException.getNotFoundInstance();
-    }
+    int nudge = moduleSize >> 1;
+    top += nudge;
+    left += nudge;
 
     // Now just read off the bits
-    BitMatrix bits = new BitMatrix(dimension);
-    for (int i = 0; i < dimension; i++) {
-      int iOffset = y + i * moduleSize;
-      for (int j = 0; j < dimension; j++) {
-        if (image.get(x + j * moduleSize, iOffset)) {
-          bits.set(j, i);
+    BitMatrix bits = new BitMatrix(matrixWidth, matrixHeight);
+    for (int y = 0; y < matrixHeight; y++) {
+      int iOffset = top + y * moduleSize;
+      for (int x = 0; x < matrixWidth; x++) {
+        if (image.get(left + x * moduleSize, iOffset)) {
+          bits.set(x, y);
         }
       }
     }
     return bits;
   }
 
+  private static int moduleSize(int[] leftTopBlack, BitMatrix image) throws NotFoundException {
+    int width = image.getWidth();
+    int x = leftTopBlack[0];
+    int y = leftTopBlack[1];
+    while (x < width && image.get(x, y)) {
+      x++;
+    }
+    if (x == width) {
+      throw NotFoundException.getNotFoundInstance();
+    }
+
+    int moduleSize = x - leftTopBlack[0];
+    if (moduleSize == 0) {
+      throw NotFoundException.getNotFoundInstance();
+    }
+    return moduleSize;
+  }
+
 }

core/src/com/google/zxing/pdf417/PDF417Reader.java

@@ -29,7 +29,6 @@ import com.google.zxing.common.DecoderResult;
 import com.google.zxing.common.DetectorResult;
 import com.google.zxing.pdf417.decoder.Decoder;
 import com.google.zxing.pdf417.detector.Detector;
-import com.google.zxing.qrcode.QRCodeReader;
 
 import java.util.Hashtable;
 
@@ -55,12 +54,11 @@ public final class PDF417Reader implements Reader {
     return decode(image, null);
   }
 
-  public Result decode(BinaryBitmap image, Hashtable hints)
-      throws NotFoundException, FormatException {
+  public Result decode(BinaryBitmap image, Hashtable hints) throws NotFoundException, FormatException {
     DecoderResult decoderResult;
     ResultPoint[] points;
     if (hints != null && hints.containsKey(DecodeHintType.PURE_BARCODE)) {
-      BitMatrix bits = QRCodeReader.extractPureBits(image.getBlackMatrix());
+      BitMatrix bits = extractPureBits(image.getBlackMatrix());
       decoderResult = decoder.decode(bits);
       points = NO_POINTS;
     } else {
@@ -76,4 +74,116 @@ public final class PDF417Reader implements Reader {
     // do nothing
   }
 
+  /**
+   * This method detects a code in a "pure" image -- that is, pure monochrome image
+   * which contains only an unrotated, unskewed, image of a code, with some white border
+   * around it. This is a specialized method that works exceptionally fast in this special
+   * case.
+   *
+   * @see com.google.zxing.qrcode.QRCodeReader#extractPureBits(BitMatrix)
+   * @see com.google.zxing.datamatrix.DataMatrixReader#extractPureBits(BitMatrix)
+   */
+  private static BitMatrix extractPureBits(BitMatrix image) throws NotFoundException {
+
+    int[] leftTopBlack = image.getTopLeftOnBit();
+    int[] rightBottomBlack = image.getBottomRightOnBit();
+    if (leftTopBlack == null || rightBottomBlack == null) {
+      throw NotFoundException.getNotFoundInstance();
+    }
+
+    int moduleSize = moduleSize(leftTopBlack, image);
+
+    int top = leftTopBlack[1];
+    int bottom = rightBottomBlack[1];
+    int left = findPatternStart(leftTopBlack[0], top, image);
+    int right = findPatternEnd(leftTopBlack[0], top, image);
+
+    int matrixWidth = (right - left + 1) / moduleSize;
+    int matrixHeight = (bottom - top + 1) / moduleSize;
+    if (matrixWidth == 0 || matrixHeight == 0) {
+      throw NotFoundException.getNotFoundInstance();
+    }
+
+    // Push in the "border" by half the module width so that we start
+    // sampling in the middle of the module. Just in case the image is a
+    // little off, this will help recover.
+    int nudge = moduleSize >> 1;
+    top += nudge;
+    left += nudge;
+
+    // Now just read off the bits
+    BitMatrix bits = new BitMatrix(matrixWidth, matrixHeight);
+    for (int y = 0; y < matrixHeight; y++) {
+      int iOffset = top + y * moduleSize;
+      for (int x = 0; x < matrixWidth; x++) {
+        if (image.get(left + x * moduleSize, iOffset)) {
+          bits.set(x, y);
+        }
+      }
+    }
+    return bits;
+  }
+
+  private static int moduleSize(int[] leftTopBlack, BitMatrix image) throws NotFoundException {
+    int x = leftTopBlack[0];
+    int y = leftTopBlack[1];
+    int width = image.getWidth();
+    while (x < width && image.get(x, y)) {
+      x++;
+    }
+    if (x == width) {
+      throw NotFoundException.getNotFoundInstance();
+    }
+
+    int moduleSize = (x - leftTopBlack[0]) >>> 3; // We've crossed left first bar, which is 8x
+    if (moduleSize == 0) {
+      throw NotFoundException.getNotFoundInstance();
+    }
+
+    return moduleSize;
+  }
+
+  private static int findPatternStart(int x, int y, BitMatrix image) throws NotFoundException {
+    int width = image.getWidth();
+    int start = x;
+    // start should be on black
+    int transitions = 0;
+    boolean black = true;
+    while (start < width - 1 && transitions < 8) {
+      start++;
+      boolean newBlack = image.get(start, y);
+      if (black != newBlack) {
+        transitions++;
+      }
+      black = newBlack;
+    }
+    if (start == width - 1) {
+      throw NotFoundException.getNotFoundInstance();
+    }
+    return start;
+  }
+
+  private static int findPatternEnd(int x, int y, BitMatrix image) throws NotFoundException {
+    int width = image.getWidth();
+    int end = width - 1;
+    // end should be on black
+    while (end > x && !image.get(end, y)) {
+      end--;
+    }
+    int transitions = 0;
+    boolean black = true;
+    while (end > x && transitions < 9) {
+      end--;
+      boolean newBlack = image.get(end, y);
+      if (black != newBlack) {
+        transitions++;
+      }
+      black = newBlack;
+    }
+    if (end == x) {
+      throw NotFoundException.getNotFoundInstance();
+    }
+    return end;
+  }
+
 }

core/src/com/google/zxing/pdf417/decoder/BitMatrixParser.java

@@ -61,8 +61,7 @@ final class BitMatrixParser {
    */
   int[] readCodewords() throws FormatException {
     int width = bitMatrix.getWidth();
-    // TODO should be a rectangular matrix
-    int height = width;
+    int height = bitMatrix.getHeight();
 
     erasures = new int[MAX_CW_CAPACITY];
 

core/src/com/google/zxing/qrcode/QRCodeReader.java

@@ -90,30 +90,65 @@ public class QRCodeReader implements Reader {
   }
 
   /**
-   * This method detects a barcode in a "pure" image -- that is, pure monochrome image
-   * which contains only an unrotated, unskewed, image of a barcode, with some white border
+   * This method detects a code in a "pure" image -- that is, pure monochrome image
+   * which contains only an unrotated, unskewed, image of a code, with some white border
    * around it. This is a specialized method that works exceptionally fast in this special
    * case.
+   *
+   * @see com.google.zxing.pdf417.PDF417Reader#extractPureBits(BitMatrix)
+   * @see com.google.zxing.datamatrix.DataMatrixReader#extractPureBits(BitMatrix)
    */
-  public static BitMatrix extractPureBits(BitMatrix image) throws NotFoundException {
+  private static BitMatrix extractPureBits(BitMatrix image) throws NotFoundException {
 
-    int height = image.getHeight();
-    int width = image.getWidth();
-    int minDimension = Math.min(height, width);
-
-    // And then keep tracking across the top-left black module to determine module size
-    //int moduleEnd = borderWidth;
     int[] leftTopBlack = image.getTopLeftOnBit();
-    if (leftTopBlack == null) {
+    int[] rightBottomBlack = image.getBottomRightOnBit();
+    if (leftTopBlack == null || rightBottomBlack == null) {
       throw NotFoundException.getNotFoundInstance();
     }
+
+    int moduleSize = moduleSize(leftTopBlack, image);
+
+    int top = leftTopBlack[1];
+    int bottom = rightBottomBlack[1];
+    int left = leftTopBlack[0];
+    int right = rightBottomBlack[0];
+
+    int matrixWidth = (right - left + 1) / moduleSize;
+    int matrixHeight = (bottom - top + 1) / moduleSize;
+    if (matrixWidth == 0 || matrixHeight == 0) {
+      throw NotFoundException.getNotFoundInstance();
+    }
+
+    // Push in the "border" by half the module width so that we start
+    // sampling in the middle of the module. Just in case the image is a
+    // little off, this will help recover.
+    int nudge = moduleSize >> 1;
+    top += nudge;
+    left += nudge;
+
+    // Now just read off the bits
+    BitMatrix bits = new BitMatrix(matrixWidth, matrixHeight);
+    for (int y = 0; y < matrixHeight; y++) {
+      int iOffset = top + y * moduleSize;
+      for (int x = 0; x < matrixWidth; x++) {
+        if (image.get(left + x * moduleSize, iOffset)) {
+          bits.set(x, y);
+        }
+      }
+    }
+    return bits;
+  }
+
+  private static int moduleSize(int[] leftTopBlack, BitMatrix image) throws NotFoundException {
+    int height = image.getHeight();
+    int width = image.getWidth();
     int x = leftTopBlack[0];
     int y = leftTopBlack[1];
-    while (x < minDimension && y < minDimension && image.get(x, y)) {
+    while (x < width && y < height && image.get(x, y)) {
       x++;
       y++;
     }
-    if (x == minDimension || y == minDimension) {
+    if (x == width || y == height) {
       throw NotFoundException.getNotFoundInstance();
     }
 
@@ -121,46 +156,7 @@ public class QRCodeReader implements Reader {
     if (moduleSize == 0) {
       throw NotFoundException.getNotFoundInstance();
     }
-
-    // And now find where the rightmost black module on the first row ends
-    int rowEndOfSymbol = width - 1;
-    while (rowEndOfSymbol > x && !image.get(rowEndOfSymbol, y)) {
-      rowEndOfSymbol--;
-    }
-    if (rowEndOfSymbol <= x) {
-      throw NotFoundException.getNotFoundInstance();
-    }
-    rowEndOfSymbol++;
-
-    // Make sure width of barcode is a multiple of module size
-    if ((rowEndOfSymbol - x) % moduleSize != 0) {
-      throw NotFoundException.getNotFoundInstance();
-    }
-    int dimension = 1 + ((rowEndOfSymbol - x) / moduleSize);
-
-    // Push in the "border" by half the module width so that we start
-    // sampling in the middle of the module. Just in case the image is a
-    // little off, this will help recover. Need to back up at least 1.
-    int backOffAmount = moduleSize == 1 ? 1 : moduleSize >> 1;
-    x -= backOffAmount;
-    y -= backOffAmount;
-
-    if ((x + (dimension - 1) * moduleSize) >= width ||
-        (y + (dimension - 1) * moduleSize) >= height) {
-      throw NotFoundException.getNotFoundInstance();
-    }
-
-    // Now just read off the bits
-    BitMatrix bits = new BitMatrix(dimension);
-    for (int i = 0; i < dimension; i++) {
-      int iOffset = y + i * moduleSize;
-      for (int j = 0; j < dimension; j++) {
-        if (image.get(x + j * moduleSize, iOffset)) {
-          bits.set(j, i);
-        }
-      }
-    }
-    return bits;
+    return moduleSize;
   }
 
 }

javase/src/com/google/zxing/client/j2se/CommandLineRunner.java

@@ -250,7 +250,7 @@ public final class CommandLineRunner {
     } catch (NotFoundException nfe) {
       System.out.println(uri.toString() + ": No barcode found");
       return null;
-    } finally {
+    // } finally {
       // Uncomment these lines when turning on exception tracking in ReaderException.
       //System.out.println("Threw " + ReaderException.getExceptionCountAndReset() + " exceptions");
       //System.out.println("Throwers:\n" + ReaderException.getThrowersAndReset());