/*
- * Copyright 2007 Google Inc.
+ * Copyright 2007 ZXing authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
package com.google.zxing.qrcode.detector;
-import com.google.zxing.MonochromeBitmapSource;
import com.google.zxing.ReaderException;
import com.google.zxing.ResultPoint;
import com.google.zxing.common.BitMatrix;
+import com.google.zxing.common.DetectorResult;
+import com.google.zxing.common.GridSampler;
import com.google.zxing.qrcode.decoder.Version;
+import java.util.Hashtable;
+
/**
- * @author srowen@google.com (Sean Owen)
+ * <p>Encapsulates logic that can detect a QR Code in an image, even if the QR Code
+ * is rotated or skewed, or partially obscured.</p>
+ *
+ * @author Sean Owen
*/
-public final class Detector {
+public class Detector {
- private final MonochromeBitmapSource image;
+ private final BitMatrix image;
- public Detector(MonochromeBitmapSource image) {
+ public Detector(BitMatrix image) {
this.image = image;
}
+ protected BitMatrix getImage() {
+ return image;
+ }
+
+ /**
+ * <p>Detects a QR Code in an image, simply.</p>
+ *
+ * @return {@link DetectorResult} encapsulating results of detecting a QR Code
+ * @throws ReaderException if no QR Code can be found
+ */
public DetectorResult detect() throws ReaderException {
+ return detect(null);
+ }
- MonochromeBitmapSource image = this.image;
+ /**
+ * <p>Detects a QR Code in an image, simply.</p>
+ *
+ * @param hints optional hints to detector
+ * @return {@link DetectorResult} encapsulating results of detecting a QR Code
+ * @throws ReaderException if no QR Code can be found
+ */
+ public DetectorResult detect(Hashtable hints) throws ReaderException {
FinderPatternFinder finder = new FinderPatternFinder(image);
- FinderPatternInfo info = finder.find();
+ FinderPatternInfo info = finder.find(hints);
+
+ return processFinderPatternInfo(info);
+ }
+
+ protected DetectorResult processFinderPatternInfo(FinderPatternInfo info) throws ReaderException {
FinderPattern topLeft = info.getTopLeft();
FinderPattern topRight = info.getTopRight();
FinderPattern bottomLeft = info.getBottomLeft();
float moduleSize = calculateModuleSize(topLeft, topRight, bottomLeft);
+ if (moduleSize < 1.0f) {
+ throw ReaderException.getInstance();
+ }
int dimension = computeDimension(topLeft, topRight, bottomLeft, moduleSize);
Version provisionalVersion = Version.getProvisionalVersionForDimension(dimension);
int modulesBetweenFPCenters = provisionalVersion.getDimensionForVersion() - 7;
- // Guess where a "bottom right" finder pattern would have been
- float bottomRightX = topRight.getX() - topLeft.getX() + bottomLeft.getX();
- float bottomRightY = topRight.getY() - topLeft.getY() + bottomLeft.getY();
-
AlignmentPattern alignmentPattern = null;
// Anything above version 1 has an alignment pattern
if (provisionalVersion.getAlignmentPatternCenters().length > 0) {
+ // Guess where a "bottom right" finder pattern would have been
+ float bottomRightX = topRight.getX() - topLeft.getX() + bottomLeft.getX();
+ float bottomRightY = topRight.getY() - topLeft.getY() + bottomLeft.getY();
+
// Estimate that alignment pattern is closer by 3 modules
// from "bottom right" to known top left location
float correctionToTopLeft = 1.0f - 3.0f / (float) modulesBetweenFPCenters;
estAlignmentY,
(float) i);
break;
- } catch (ReaderException de) {
+ } catch (ReaderException re) {
// try next round
}
}
- if (alignmentPattern == null) {
- throw new ReaderException("Could not find alignment pattern");
- }
-
+ // If we didn't find alignment pattern... well try anyway without it
}
- GridSampler sampler = GridSampler.getInstance();
- BitMatrix bits = sampler.sampleGrid(image,
- topLeft,
- topRight,
- bottomLeft,
- alignmentPattern,
- dimension);
-
- /*
- try {
- BufferedImage outImage =
- new BufferedImage(dimension,
- dimension,
- BufferedImage.TYPE_BYTE_BINARY);
- for (int i = 0; i < dimension; i++) {
- for (int j = 0; j < dimension; j++) {
- if (bits.get(i, j)) {
- outImage.setRGB(j, i, 0xFF000000);
- } else {
- outImage.setRGB(j, i, 0xFFFFFFFF);
- }
- }
- }
- ImageIO.write(outImage, "PNG",
- new File("/home/srowen/out.png"));
- } catch (IOException ioe) {
- ioe.printStackTrace();
- }
- */
+ BitMatrix bits = sampleGrid(image, topLeft, topRight, bottomLeft, alignmentPattern, dimension);
ResultPoint[] points;
if (alignmentPattern == null) {
- points = new ResultPoint[] { bottomLeft, topLeft, topRight };
+ points = new ResultPoint[]{bottomLeft, topLeft, topRight};
} else {
- points = new ResultPoint[] { bottomLeft, topLeft, topRight, alignmentPattern };
+ points = new ResultPoint[]{bottomLeft, topLeft, topRight, alignmentPattern};
}
return new DetectorResult(bits, points);
}
+ private static BitMatrix sampleGrid(BitMatrix image,
+ ResultPoint topLeft,
+ ResultPoint topRight,
+ ResultPoint bottomLeft,
+ ResultPoint alignmentPattern,
+ int dimension) throws ReaderException {
+ float dimMinusThree = (float) dimension - 3.5f;
+ float bottomRightX;
+ float bottomRightY;
+ float sourceBottomRightX;
+ float sourceBottomRightY;
+ if (alignmentPattern != null) {
+ bottomRightX = alignmentPattern.getX();
+ bottomRightY = alignmentPattern.getY();
+ sourceBottomRightX = sourceBottomRightY = dimMinusThree - 3.0f;
+ } else {
+ // Don't have an alignment pattern, just make up the bottom-right point
+ bottomRightX = (topRight.getX() - topLeft.getX()) + bottomLeft.getX();
+ bottomRightY = (topRight.getY() - topLeft.getY()) + bottomLeft.getY();
+ sourceBottomRightX = sourceBottomRightY = dimMinusThree;
+ }
+
+ GridSampler sampler = GridSampler.getInstance();
+ return sampler.sampleGrid(
+ image,
+ dimension,
+ 3.5f,
+ 3.5f,
+ dimMinusThree,
+ 3.5f,
+ sourceBottomRightX,
+ sourceBottomRightY,
+ 3.5f,
+ dimMinusThree,
+ topLeft.getX(),
+ topLeft.getY(),
+ topRight.getX(),
+ topRight.getY(),
+ bottomRightX,
+ bottomRightY,
+ bottomLeft.getX(),
+ bottomLeft.getY());
+ }
+
+ /**
+ * <p>Computes the dimension (number of modules on a size) of the QR Code based on the position
+ * of the finder patterns and estimated module size.</p>
+ */
private static int computeDimension(ResultPoint topLeft,
ResultPoint topRight,
ResultPoint bottomLeft,
- float moduleSize)
- throws ReaderException {
- int tltrCentersDimension =
- round(FinderPatternFinder.distance(topLeft, topRight) / moduleSize);
- int tlblCentersDimension =
- round(FinderPatternFinder.distance(topLeft, bottomLeft) / moduleSize);
+ float moduleSize) throws ReaderException {
+ int tltrCentersDimension = round(ResultPoint.distance(topLeft, topRight) / moduleSize);
+ int tlblCentersDimension = round(ResultPoint.distance(topLeft, bottomLeft) / moduleSize);
int dimension = ((tltrCentersDimension + tlblCentersDimension) >> 1) + 7;
switch (dimension & 0x03) { // mod 4
case 0:
dimension--;
break;
case 3:
- throw new ReaderException("Bad dimension: " + dimension);
+ throw ReaderException.getInstance();
}
return dimension;
}
- private float calculateModuleSize(ResultPoint topLeft,
- ResultPoint topRight,
- ResultPoint bottomLeft) {
+ /**
+ * <p>Computes an average estimated module size based on estimated derived from the positions
+ * of the three finder patterns.</p>
+ */
+ private float calculateModuleSize(ResultPoint topLeft, ResultPoint topRight,
+ ResultPoint bottomLeft) {
// Take the average
return (calculateModuleSizeOneWay(topLeft, topRight) +
- calculateModuleSizeOneWay(topLeft, bottomLeft)) / 2.0f;
+ calculateModuleSizeOneWay(topLeft, bottomLeft)) / 2.0f;
}
- private float calculateModuleSizeOneWay(ResultPoint pattern,
- ResultPoint otherPattern) {
+ /**
+ * <p>Estimates module size based on two finder patterns -- it uses
+ * {@link #sizeOfBlackWhiteBlackRunBothWays(int, int, int, int)} to figure the
+ * width of each, measuring along the axis between their centers.</p>
+ */
+ private float calculateModuleSizeOneWay(ResultPoint pattern, ResultPoint otherPattern) {
float moduleSizeEst1 = sizeOfBlackWhiteBlackRunBothWays((int) pattern.getX(),
- (int) pattern.getY(),
- (int) otherPattern.getX(),
- (int) otherPattern.getY());
+ (int) pattern.getY(),
+ (int) otherPattern.getX(),
+ (int) otherPattern.getY());
float moduleSizeEst2 = sizeOfBlackWhiteBlackRunBothWays((int) otherPattern.getX(),
- (int) otherPattern.getY(),
- (int) pattern.getX(),
- (int) pattern.getY());
+ (int) otherPattern.getY(),
+ (int) pattern.getX(),
+ (int) pattern.getY());
if (Float.isNaN(moduleSizeEst1)) {
return moduleSizeEst2;
}
return (moduleSizeEst1 + moduleSizeEst2) / 14.0f;
}
+ /**
+ * See {@link #sizeOfBlackWhiteBlackRun(int, int, int, int)}; computes the total width of
+ * a finder pattern by looking for a black-white-black run from the center in the direction
+ * of another point (another finder pattern center), and in the opposite direction too.</p>
+ */
private float sizeOfBlackWhiteBlackRunBothWays(int fromX, int fromY, int toX, int toY) {
+
float result = sizeOfBlackWhiteBlackRun(fromX, fromY, toX, toY);
- result += sizeOfBlackWhiteBlackRun(fromX, fromY, fromX - (toX - fromX), fromY - (toY - fromY));
+
+ // Now count other way -- don't run off image though of course
+ int otherToX = fromX - (toX - fromX);
+ if (otherToX < 0) {
+ // "to" should the be the first value not included, so, the first value off
+ // the edge is -1
+ otherToX = -1;
+ } else if (otherToX >= image.getWidth()) {
+ otherToX = image.getWidth();
+ }
+ int otherToY = fromY - (toY - fromY);
+ if (otherToY < 0) {
+ otherToY = -1;
+ } else if (otherToY >= image.getHeight()) {
+ otherToY = image.getHeight();
+ }
+ result += sizeOfBlackWhiteBlackRun(fromX, fromY, otherToX, otherToY);
return result - 1.0f; // -1 because we counted the middle pixel twice
}
+ /**
+ * <p>This method traces a line from a point in the image, in the direction towards another point.
+ * It begins in a black region, and keeps going until it finds white, then black, then white again.
+ * It reports the distance from the start to this point.</p>
+ *
+ * <p>This is used when figuring out how wide a finder pattern is, when the finder pattern
+ * may be skewed or rotated.</p>
+ */
private float sizeOfBlackWhiteBlackRun(int fromX, int fromY, int toX, int toY) {
// Mild variant of Bresenham's algorithm;
// see http://en.wikipedia.org/wiki/Bresenham's_line_algorithm
int realX = steep ? y : x;
int realY = steep ? x : y;
if (state == 1) { // In white pixels, looking for black
- if (image.isBlack(realX, realY)) {
+ if (image.get(realX, realY)) {
state++;
}
} else {
- if (!image.isBlack(realX, realY)) {
+ if (!image.get(realX, realY)) {
state++;
}
}
error -= dx;
}
}
- // Hmm, couldn't find all of what we wanted -- don't know
- return Float.NaN;
+ int diffX = toX - fromX;
+ int diffY = toY - fromY;
+ return (float) Math.sqrt((double) (diffX * diffX + diffY * diffY));
}
+ /**
+ * <p>Attempts to locate an alignment pattern in a limited region of the image, which is
+ * guessed to contain it. This method uses {@link AlignmentPattern}.</p>
+ *
+ * @param overallEstModuleSize estimated module size so far
+ * @param estAlignmentX x coordinate of center of area probably containing alignment pattern
+ * @param estAlignmentY y coordinate of above
+ * @param allowanceFactor number of pixels in all directions to search from the center
+ * @return {@link AlignmentPattern} if found, or null otherwise
+ * @throws ReaderException if an unexpected error occurs during detection
+ */
private AlignmentPattern findAlignmentInRegion(float overallEstModuleSize,
int estAlignmentX,
int estAlignmentY,
// should be
int allowance = (int) (allowanceFactor * overallEstModuleSize);
int alignmentAreaLeftX = Math.max(0, estAlignmentX - allowance);
- int alignmentAreaRightX = Math.min(image.getWidth() - 1,
- estAlignmentX + allowance);
+ int alignmentAreaRightX = Math.min(image.getWidth() - 1, estAlignmentX + allowance);
+ if (alignmentAreaRightX - alignmentAreaLeftX < overallEstModuleSize * 3) {
+ throw ReaderException.getInstance();
+ }
+
int alignmentAreaTopY = Math.max(0, estAlignmentY - allowance);
- int alignmentAreaBottomY = Math.min(image.getHeight() - 1,
- estAlignmentY + allowance);
+ int alignmentAreaBottomY = Math.min(image.getHeight() - 1, estAlignmentY + allowance);
AlignmentPatternFinder alignmentFinder =
new AlignmentPatternFinder(
}
/**
- * Ends up being a bit faster than Math.round()
+ * Ends up being a bit faster than Math.round(). This merely rounds its argument to the nearest int,
+ * where x.5 rounds up.
*/
private static int round(float d) {
return (int) (d + 0.5f);
projects / zxing.git / blobdiff