package com.google.zxing.oned;
+import com.google.zxing.BinaryBitmap;
+import com.google.zxing.DecodeHintType;
import com.google.zxing.Reader;
import com.google.zxing.ReaderException;
import com.google.zxing.Result;
+import com.google.zxing.ResultMetadataType;
+import com.google.zxing.ResultPoint;
import com.google.zxing.common.BitArray;
import java.util.Hashtable;
/**
- * <p>{@link Reader}s which also implement this interface read one-dimensional barcode
- * formats, and expose additional functionality that is specific to this type of barcode.</p>
+ * Encapsulates functionality and implementation that is common to all families
+ * of one-dimensional barcodes.
*
+ * @author dswitkin@google.com (Daniel Switkin)
* @author Sean Owen
*/
-public interface OneDReader extends Reader {
+public abstract class OneDReader implements Reader {
+
+ private static final int INTEGER_MATH_SHIFT = 8;
+ static final int PATTERN_MATCH_RESULT_SCALE_FACTOR = 1 << INTEGER_MATH_SHIFT;
+
+ public Result decode(BinaryBitmap image) throws ReaderException {
+ return decode(image, null);
+ }
+
+ // Note that we don't try rotation without the try harder flag, even if rotation was supported.
+ public Result decode(BinaryBitmap image, Hashtable hints) throws ReaderException {
+ try {
+ return doDecode(image, hints);
+ } catch (ReaderException re) {
+ boolean tryHarder = hints != null && hints.containsKey(DecodeHintType.TRY_HARDER);
+ if (tryHarder && image.isRotateSupported()) {
+ BinaryBitmap rotatedImage = image.rotateCounterClockwise();
+ Result result = doDecode(rotatedImage, hints);
+ // Record that we found it rotated 90 degrees CCW / 270 degrees CW
+ Hashtable metadata = result.getResultMetadata();
+ int orientation = 270;
+ if (metadata != null && metadata.containsKey(ResultMetadataType.ORIENTATION)) {
+ // But if we found it reversed in doDecode(), add in that result here:
+ orientation = (orientation +
+ ((Integer) metadata.get(ResultMetadataType.ORIENTATION)).intValue()) % 360;
+ }
+ result.putMetadata(ResultMetadataType.ORIENTATION, new Integer(orientation));
+ return result;
+ } else {
+ throw re;
+ }
+ }
+ }
+
+ /**
+ * We're going to examine rows from the middle outward, searching alternately above and below the
+ * middle, and farther out each time. rowStep is the number of rows between each successive
+ * attempt above and below the middle. So we'd scan row middle, then middle - rowStep, then
+ * middle + rowStep, then middle - (2 * rowStep), etc.
+ * rowStep is bigger as the image is taller, but is always at least 1. We've somewhat arbitrarily
+ * decided that moving up and down by about 1/16 of the image is pretty good; we try more of the
+ * image if "trying harder".
+ *
+ * @param image The image to decode
+ * @param hints Any hints that were requested
+ * @return The contents of the decoded barcode
+ * @throws ReaderException Any spontaneous errors which occur
+ */
+ private Result doDecode(BinaryBitmap image, Hashtable hints) throws ReaderException {
+ int width = image.getWidth();
+ int height = image.getHeight();
+ BitArray row = new BitArray(width);
+
+ int middle = height >> 1;
+ boolean tryHarder = hints != null && hints.containsKey(DecodeHintType.TRY_HARDER);
+ int rowStep = Math.max(1, height >> (tryHarder ? 7 : 4));
+ int maxLines;
+ if (tryHarder) {
+ maxLines = height; // Look at the whole image, not just the center
+ } else {
+ maxLines = 9; // Nine rows spaced 1/16 apart is roughly the middle half of the image
+ }
+
+ for (int x = 0; x < maxLines; x++) {
+
+ // Scanning from the middle out. Determine which row we're looking at next:
+ int rowStepsAboveOrBelow = (x + 1) >> 1;
+ boolean isAbove = (x & 0x01) == 0; // i.e. is x even?
+ int rowNumber = middle + rowStep * (isAbove ? rowStepsAboveOrBelow : -rowStepsAboveOrBelow);
+ if (rowNumber < 0 || rowNumber >= height) {
+ // Oops, if we run off the top or bottom, stop
+ break;
+ }
+
+ // Estimate black point for this row and load it:
+ try {
+ row = image.getBlackRow(rowNumber, row);
+ } catch (ReaderException re) {
+ continue;
+ }
+
+ // While we have the image data in a BitArray, it's fairly cheap to reverse it in place to
+ // handle decoding upside down barcodes.
+ for (int attempt = 0; attempt < 2; attempt++) {
+ if (attempt == 1) { // trying again?
+ row.reverse(); // reverse the row and continue
+ // This means we will only ever draw result points *once* in the life of this method
+ // since we want to avoid drawing the wrong points after flipping the row, and,
+ // don't want to clutter with noise from every single row scan -- just the scans
+ // that start on the center line.
+ if (hints != null && hints.containsKey(DecodeHintType.NEED_RESULT_POINT_CALLBACK)) {
+ hints = (Hashtable) hints.clone();
+ hints.remove(DecodeHintType.NEED_RESULT_POINT_CALLBACK);
+ }
+ }
+ try {
+ // Look for a barcode
+ Result result = decodeRow(rowNumber, row, hints);
+ // We found our barcode
+ if (attempt == 1) {
+ // But it was upside down, so note that
+ result.putMetadata(ResultMetadataType.ORIENTATION, new Integer(180));
+ // And remember to flip the result points horizontally.
+ ResultPoint[] points = result.getResultPoints();
+ points[0] = new ResultPoint(width - points[0].getX() - 1, points[0].getY());
+ points[1] = new ResultPoint(width - points[1].getX() - 1, points[1].getY());
+ }
+ return result;
+ } catch (ReaderException re) {
+ // continue -- just couldn't decode this row
+ }
+ }
+ }
+
+ throw ReaderException.getInstance();
+ }
+
+ /**
+ * Records the size of successive runs of white and black pixels in a row, starting at a given point.
+ * The values are recorded in the given array, and the number of runs recorded is equal to the size
+ * of the array. If the row starts on a white pixel at the given start point, then the first count
+ * recorded is the run of white pixels starting from that point; likewise it is the count of a run
+ * of black pixels if the row begin on a black pixels at that point.
+ *
+ * @param row row to count from
+ * @param start offset into row to start at
+ * @param counters array into which to record counts
+ * @throws ReaderException if counters cannot be filled entirely from row before running out
+ * of pixels
+ */
+ static void recordPattern(BitArray row, int start, int[] counters) throws ReaderException {
+ int numCounters = counters.length;
+ for (int i = 0; i < numCounters; i++) {
+ counters[i] = 0;
+ }
+ int end = row.getSize();
+ if (start >= end) {
+ throw ReaderException.getInstance();
+ }
+ boolean isWhite = !row.get(start);
+ int counterPosition = 0;
+ int i = start;
+ while (i < end) {
+ boolean pixel = row.get(i);
+ if (pixel ^ isWhite) { // that is, exactly one is true
+ counters[counterPosition]++;
+ } else {
+ counterPosition++;
+ if (counterPosition == numCounters) {
+ break;
+ } else {
+ counters[counterPosition] = 1;
+ isWhite = !isWhite;
+ }
+ }
+ i++;
+ }
+ // If we read fully the last section of pixels and filled up our counters -- or filled
+ // the last counter but ran off the side of the image, OK. Otherwise, a problem.
+ if (!(counterPosition == numCounters || (counterPosition == numCounters - 1 && i == end))) {
+ throw ReaderException.getInstance();
+ }
+ }
+
+ /**
+ * Determines how closely a set of observed counts of runs of black/white values matches a given
+ * target pattern. This is reported as the ratio of the total variance from the expected pattern
+ * proportions across all pattern elements, to the length of the pattern.
+ *
+ * @param counters observed counters
+ * @param pattern expected pattern
+ * @param maxIndividualVariance The most any counter can differ before we give up
+ * @return ratio of total variance between counters and pattern compared to total pattern size,
+ * where the ratio has been multiplied by 256. So, 0 means no variance (perfect match); 256 means
+ * the total variance between counters and patterns equals the pattern length, higher values mean
+ * even more variance
+ */
+ static int patternMatchVariance(int[] counters, int[] pattern, int maxIndividualVariance) {
+ int numCounters = counters.length;
+ int total = 0;
+ int patternLength = 0;
+ for (int i = 0; i < numCounters; i++) {
+ total += counters[i];
+ patternLength += pattern[i];
+ }
+ if (total < patternLength) {
+ // If we don't even have one pixel per unit of bar width, assume this is too small
+ // to reliably match, so fail:
+ return Integer.MAX_VALUE;
+ }
+ // We're going to fake floating-point math in integers. We just need to use more bits.
+ // Scale up patternLength so that intermediate values below like scaledCounter will have
+ // more "significant digits"
+ int unitBarWidth = (total << INTEGER_MATH_SHIFT) / patternLength;
+ maxIndividualVariance = (maxIndividualVariance * unitBarWidth) >> INTEGER_MATH_SHIFT;
+
+ int totalVariance = 0;
+ for (int x = 0; x < numCounters; x++) {
+ int counter = counters[x] << INTEGER_MATH_SHIFT;
+ int scaledPattern = pattern[x] * unitBarWidth;
+ int variance = counter > scaledPattern ? counter - scaledPattern : scaledPattern - counter;
+ if (variance > maxIndividualVariance) {
+ return Integer.MAX_VALUE;
+ }
+ totalVariance += variance;
+ }
+ return totalVariance / total;
+ }
/**
* <p>Attempts to decode a one-dimensional barcode format given a single row of
* @return {@link Result} containing encoded string and start/end of barcode
* @throws ReaderException if an error occurs or barcode cannot be found
*/
- Result decodeRow(int rowNumber, BitArray row, Hashtable hints) throws ReaderException;
+ public abstract Result decodeRow(int rowNumber, BitArray row, Hashtable hints)
+ throws ReaderException;
-}
\ No newline at end of file
+}
projects / zxing.git / blobdiff