import com.google.zxing.ResultPoint;
/**
+ * <p>Encapsulates an alignment pattern, which are the smaller square patterns found in
+ * all but the simplest QR Codes.</p>
+ *
* @author srowen@google.com (Sean Owen)
*/
public final class AlignmentPattern implements ResultPoint {
return estimatedModuleSize;
}
+ /**
+ * <p>Determines if this alignment pattern "about equals" an alignment pattern at the stated
+ * position and size -- meaning, it is at nearly the same center with nearly the same size.</p>
+ */
boolean aboutEquals(float moduleSize, float i, float j) {
return
Math.abs(i - posY) <= moduleSize &&
import java.util.Vector;\r
\r
/**\r
+ * <p>This class attempts to find alignment patterns in a QR Code. Alignment patterns look like finder\r
+ * patterns but are smaller and appear at regular intervals throughout the image.</p>\r
+ *\r
* <p>At the moment this only looks for the bottom-right alignment pattern.</p>\r
*\r
+ * <p>This is mostly a simplified copy of {@link FinderPatternFinder}. It is copied,\r
+ * pasted and stripped down here for maximum performance but does unfortunately duplicate\r
+ * some code.</p>\r
+ *\r
* <p>This class is not thread-safe.</p>\r
*\r
* @author srowen@google.com (Sean Owen)\r
private final int height;\r
private final float moduleSize;\r
\r
+ /**\r
+ * <p>Creates a finder that will look in a portion of the whole image.</p>\r
+ *\r
+ * @param image image to search\r
+ * @param startX left column from which to start searching\r
+ * @param startY top row from which to start searching\r
+ * @param width width of region to search\r
+ * @param height height of region to search\r
+ * @param moduleSize estimated module size so far\r
+ */\r
AlignmentPatternFinder(MonochromeBitmapSource image,\r
int startX,\r
int startY,\r
this.moduleSize = moduleSize;\r
}\r
\r
+ /**\r
+ * <p>This method attempts to find the bottom-right alignment pattern in the image. It is a bit messy since\r
+ * it's pretty performance-critical and so is written to be fast foremost.</p>\r
+ *\r
+ * @return {@link AlignmentPattern} if found\r
+ * @throws ReaderException if not found\r
+ */\r
AlignmentPattern find() throws ReaderException {\r
int startX = this.startX;\r
int height = this.height;\r
int maxJ = startX + width;\r
int middleI = startY + (height >> 1);\r
BitArray luminanceRow = new BitArray(width);\r
- int[] stateCount = new int[3]; // looking for 1 1 1\r
+ // We are looking for black/white/black modules in 1:1:1 ratio;\r
+ // this tracks the number of black/white/black modules seen so far\r
+ int[] stateCount = new int[3];\r
for (int iGen = 0; iGen < height; iGen++) {\r
// Search from middle outwards\r
- int i = middleI +\r
- ((iGen & 0x01) == 0 ? ((iGen + 1) >> 1) : -((iGen + 1) >> 1));\r
+ int i = middleI + ((iGen & 0x01) == 0 ? ((iGen + 1) >> 1) : -((iGen + 1) >> 1));\r
image.getBlackRow(i, luminanceRow, startX, width);\r
stateCount[0] = 0;\r
stateCount[1] = 0;\r
} else { // Counting white pixels\r
if (currentState == 2) { // A winner?\r
if (foundPatternCross(stateCount)) { // Yes\r
- AlignmentPattern confirmed =\r
- handlePossibleCenter(stateCount, i, j);\r
+ AlignmentPattern confirmed = handlePossibleCenter(stateCount, i, j);\r
if (confirmed != null) {\r
return confirmed;\r
}\r
throw new ReaderException("Could not find alignment pattern");\r
}\r
\r
+ /**\r
+ * Given a count of black/white/black pixels just seen and an end position,\r
+ * figures the location of the center of this black/white/black run.\r
+ */\r
private static float centerFromEnd(int[] stateCount, int end) {\r
return (float) (end - stateCount[2]) - stateCount[1] / 2.0f;\r
}\r
\r
+ /**\r
+ * @param stateCount count of black/white/black pixels just read\r
+ * @return true iff the proportions of the counts is close enough to the 1/1/1 ratios\r
+ * used by alignment patterns to be considered a match\r
+ */\r
private boolean foundPatternCross(int[] stateCount) {\r
float moduleSize = this.moduleSize;\r
for (int i = 0; i < 3; i++) {\r
return true;\r
}\r
\r
+ /**\r
+ * <p>After a horizontal scan finds a potential alignment pattern, this method\r
+ * "cross-checks" by scanning down vertically through the center of the possible\r
+ * alignment pattern to see if the same proportion is detected.</p>\r
+ *\r
+ * @param startI row where an alignment pattern was detected\r
+ * @param centerJ center of the section that appears to cross an alignment pattern\r
+ * @param maxCount maximum reasonable number of modules that should be\r
+ * observed in any reading state, based on the results of the horizontal scan\r
+ * @return vertical center of alignment pattern, or {@link Float#NaN} if not found\r
+ */\r
private float crossCheckVertical(int startI, int centerJ, int maxCount) {\r
MonochromeBitmapSource image = this.image;\r
\r
int maxI = image.getHeight();\r
int[] stateCount = new int[3];\r
+\r
+ // Start counting up from center\r
int i = startI;\r
while (i >= 0 && image.isBlack(centerJ, i) && stateCount[1] <= maxCount) {\r
stateCount[1]++;\r
i--;\r
}\r
+ // If already too many modules in this state or ran off the edge:\r
if (i < 0 || stateCount[1] > maxCount) {\r
return Float.NaN;\r
}\r
return Float.NaN;\r
}\r
\r
+ // Now also count down from center\r
i = startI + 1;\r
- while (i < maxI && image.isBlack(centerJ, i) &&\r
- stateCount[1] <= maxCount) {\r
+ while (i < maxI && image.isBlack(centerJ, i) && stateCount[1] <= maxCount) {\r
stateCount[1]++;\r
i++;\r
}\r
if (i == maxI || stateCount[1] > maxCount) {\r
return Float.NaN;\r
}\r
- while (i < maxI && !image.isBlack(centerJ, i) &&\r
- stateCount[2] <= maxCount) {\r
+ while (i < maxI && !image.isBlack(centerJ, i) && stateCount[2] <= maxCount) {\r
stateCount[2]++;\r
i++;\r
}\r
return Float.NaN;\r
}\r
\r
- return\r
- foundPatternCross(stateCount) ?\r
- centerFromEnd(stateCount, i) :\r
- Float.NaN;\r
+ return foundPatternCross(stateCount) ? centerFromEnd(stateCount, i) : Float.NaN;\r
}\r
\r
- private AlignmentPattern handlePossibleCenter(int[] stateCount,\r
- int i,\r
- int j) {\r
+ /**\r
+ * <p>This is called when a horizontal scan finds a possible alignment pattern. It will\r
+ * cross check with a vertical scan, and if successful, will see if this pattern had been\r
+ * found on a previous horizontal scan. If so, we consider it confirmed and conclude we have\r
+ * found the alignment pattern.</p>\r
+ *\r
+ * @param stateCount reading state module counts from horizontal scan\r
+ * @param i row where alignment pattern may be found\r
+ * @param j end of possible alignment pattern in row\r
+ * @return {@link AlignmentPattern} if we have found the same pattern twice, or null if not\r
+ */\r
+ private AlignmentPattern handlePossibleCenter(int[] stateCount, int i, int j) {\r
float centerJ = centerFromEnd(stateCount, j);\r
float centerI = crossCheckVertical(i, (int) centerJ, 2 * stateCount[1]);\r
if (!Float.isNaN(centerI)) {\r
- float estimatedModuleSize = (float) (stateCount[0] +\r
- stateCount[1] +\r
- stateCount[2]) / 3.0f;\r
+ float estimatedModuleSize = (float) (stateCount[0] + stateCount[1] + stateCount[2]) / 3.0f;\r
int max = possibleCenters.size();\r
for (int index = 0; index < max; index++) {\r
AlignmentPattern center = (AlignmentPattern) possibleCenters.elementAt(index);\r
import com.google.zxing.qrcode.decoder.Version;
/**
+ * <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 srowen@google.com (Sean Owen)
*/
public final class Detector {
this.image = 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 {
MonochromeBitmapSource image = this.image;
estAlignmentY,
(float) i);
break;
- } catch (ReaderException de) {
+ } catch (ReaderException re) {
// try next round
}
}
}
GridSampler sampler = GridSampler.getInstance();
- BitMatrix bits = sampler.sampleGrid(image,
- topLeft,
- topRight,
- bottomLeft,
- alignmentPattern,
- dimension);
+ BitMatrix bits = sampler.sampleGrid(image, topLeft, topRight, bottomLeft, alignmentPattern, dimension);
/*
try {
}
}
}
- ImageIO.write(outImage, "PNG",
- new File("/home/srowen/out.png"));
+ ImageIO.write(outImage, "PNG", new File("/tmp/out.png"));
} catch (IOException ioe) {
ioe.printStackTrace();
}
return new DetectorResult(bits, points);
}
+ /**
+ * <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(FinderPatternFinder.distance(topLeft, topRight) / moduleSize);
+ int tlblCentersDimension = round(FinderPatternFinder.distance(topLeft, bottomLeft) / moduleSize);
int dimension = ((tltrCentersDimension + tlblCentersDimension) >> 1) + 7;
switch (dimension & 0x03) { // mod 4
case 0:
dimension++;
break;
- // 1? do nothing
+ // 1? do nothing
case 2:
dimension--;
break;
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;
}
- 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(),
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));
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
return Float.NaN;
}
+ /**
+ * <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 directons 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);
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);
import com.google.zxing.ResultPoint;
/**
+ * <p>Encapsulates a finder pattern, which are the three square patterns found in
+ * the corners of QR Codes. It also encapsulates a count of similar finder patterns,
+ * as a convenience to {@link FinderPatternFinder}'s bookkeeping.</p>
+ *
* @author srowen@google.com (Sean Owen)
*/
public final class FinderPattern implements ResultPoint {
this.count++;
}
+ /**
+ * <p>Determines if this finder pattern "about equals" a finder pattern at the stated
+ * position and size -- meaning, it is at nearly the same center with nearly the same size.</p>
+ */
boolean aboutEquals(float moduleSize, float i, float j) {
return Math.abs(i - posY) <= moduleSize &&
Math.abs(j - posX) <= moduleSize &&
import java.util.Vector;\r
\r
/**\r
+ * <p>This class attempts to find finder patterns in a QR Code. Finder patterns are the square\r
+ * markers at three corners of a QR Code.</p>\r
+ *\r
* <p>This class is not thread-safe and should not be reused.</p>\r
*\r
* @author srowen@google.com (Sean Owen)\r
private final Vector possibleCenters;\r
private boolean hasSkipped;\r
\r
+ /**\r
+ * <p>Creates a finder that will search the image for three finder patterns.</p>\r
+ *\r
+ * @param image image to search\r
+ */\r
FinderPatternFinder(MonochromeBitmapSource image) {\r
this.image = image;\r
this.possibleCenters = new Vector(5);\r
FinderPatternInfo find() throws ReaderException {\r
int maxI = image.getHeight();\r
int maxJ = image.getWidth();\r
- int[] stateCount = new int[5]; // looking for 1 1 3 1 1\r
+ // We are looking for black/white/black/white/black modules in\r
+ // 1:1:3:1:1 ratio; this tracks the number of such modules seen so far\r
+ int[] stateCount = new int[5];\r
boolean done = false;\r
// We can afford to examine every few lines until we've started finding\r
// the patterns\r
int iSkip = BIG_SKIP;\r
for (int i = iSkip - 1; i < maxI && !done; i += iSkip) {\r
- BitArray luminanceRow = image.getBlackRow(i, null, 0, maxJ);\r
+ // Get a row of black/white values\r
+ BitArray blackRow = image.getBlackRow(i, null, 0, maxJ);\r
stateCount[0] = 0;\r
stateCount[1] = 0;\r
stateCount[2] = 0;\r
stateCount[4] = 0;\r
int currentState = 0;\r
for (int j = 0; j < maxJ; j++) {\r
- if (luminanceRow.get(j)) {\r
+ if (blackRow.get(j)) {\r
// Black pixel\r
if ((currentState & 1) == 1) { // Counting white pixels\r
currentState++;\r
if ((currentState & 1) == 0) { // Counting black pixels\r
if (currentState == 4) { // A winner?\r
if (foundPatternCross(stateCount)) { // Yes\r
- boolean confirmed =\r
- handlePossibleCenter(stateCount, i, j);\r
+ boolean confirmed = handlePossibleCenter(stateCount, i, j);\r
if (confirmed) {\r
iSkip = 1; // Go back to examining each line\r
if (hasSkipped) {\r
// Advance to next black pixel\r
do {\r
j++;\r
- } while (j < maxJ && !luminanceRow.get(j));\r
+ } while (j < maxJ && !blackRow.get(j));\r
j--; // back up to that last white pixel\r
}\r
// Clear state to start looking again\r
totalModuleSize += patternInfo[i].getEstimatedModuleSize();\r
}\r
\r
- return new FinderPatternInfo(totalModuleSize / (float) patternInfo.length,\r
- patternInfo);\r
+ return new FinderPatternInfo(totalModuleSize / (float) patternInfo.length, patternInfo);\r
}\r
\r
+ /**\r
+ * Given a count of black/white/black/white/black pixels just seen and an end position,\r
+ * figures the location of the center of this run.\r
+ */\r
private static float centerFromEnd(int[] stateCount, int end) {\r
return (float) (end - stateCount[4] - stateCount[3]) - stateCount[2] / 2.0f;\r
}\r
\r
+ /**\r
+ * @param stateCount count of black/white/black/white/black pixels just read\r
+ * @return true iff the proportions of the counts is close enough to the 1/13/1/1 ratios\r
+ * used by finder patterns to be considered a match\r
+ */\r
private static boolean foundPatternCross(int[] stateCount) {\r
int totalModuleSize = 0;\r
for (int i = 0; i < 5; i++) {\r
}\r
int moduleSize = totalModuleSize / 7;\r
// Allow less than 50% deviance from 1-1-3-1-1 pattern\r
- return\r
- Math.abs(moduleSize - stateCount[0]) << 1 <= moduleSize &&\r
+ return Math.abs(moduleSize - stateCount[0]) << 1 <= moduleSize &&\r
Math.abs(moduleSize - stateCount[1]) << 1 <= moduleSize &&\r
Math.abs(3 * moduleSize - stateCount[2]) << 1 <= 3 * moduleSize &&\r
Math.abs(moduleSize - stateCount[3]) << 1 <= moduleSize &&\r
Math.abs(moduleSize - stateCount[4]) << 1 <= moduleSize;\r
}\r
\r
+ /**\r
+ * <p>After a horizontal scan finds a potential finder pattern, this method\r
+ * "cross-checks" by scanning down vertically through the center of the possible\r
+ * finder pattern to see if the same proportion is detected.</p>\r
+ *\r
+ * @param startI row where a finder pattern was detected\r
+ * @param centerJ center of the section that appears to cross a finder pattern\r
+ * @param maxCount maximum reasonable number of modules that should be\r
+ * observed in any reading state, based on the results of the horizontal scan\r
+ * @return vertical center of finder pattern, or {@link Float#NaN} if not found\r
+ */\r
private float crossCheckVertical(int startI, int centerJ, int maxCount) {\r
MonochromeBitmapSource image = this.image;\r
\r
int maxI = image.getHeight();\r
int[] stateCount = new int[5];\r
\r
+ // Start counting up from center\r
int i = startI;\r
while (i >= 0 && image.isBlack(centerJ, i)) {\r
stateCount[2]++;\r
return Float.NaN;\r
}\r
\r
+ // Now also count down from center\r
i = startI + 1;\r
while (i < maxI && image.isBlack(centerJ, i)) {\r
stateCount[2]++;\r
return foundPatternCross(stateCount) ? centerFromEnd(stateCount, i) : Float.NaN;\r
}\r
\r
+ /**\r
+ * <p>Like {@link #crossCheckVertical(int, int, int)}, and in fact is basically identical,\r
+ * except it reads horizontally instead of vertically. This is used to cross-cross\r
+ * check a vertical cross check and locate the real center of the alignment pattern.</p>\r
+ */\r
private float crossCheckHorizontal(int startJ, int centerI, int maxCount) {\r
MonochromeBitmapSource image = this.image;\r
\r
stateCount[1]++;\r
j--;\r
}\r
- // If already too many modules in this state or ran off the edge:\r
if (j < 0 || stateCount[1] > maxCount) {\r
return Float.NaN;\r
}\r
return foundPatternCross(stateCount) ? centerFromEnd(stateCount, j) : Float.NaN;\r
}\r
\r
+ /**\r
+ * <p>This is called when a horizontal scan finds a possible alignment pattern. It will\r
+ * cross check with a vertical scan, and if successful, will, ah, cross-cross-check\r
+ * with another horizontal scan. This is needed primarily to locate the real horizontal\r
+ * center of the pattern in cases of extreme skew.</p>\r
+ *\r
+ * <p>If that succeeds the finder pattern location is added to a list that tracks\r
+ * the number of times each location has been nearly-matched as a finder pattern.\r
+ * Each additional find is more evidence that the location is in fact a finder\r
+ * pattern center\r
+ *\r
+ * @param stateCount reading state module counts from horizontal scan\r
+ * @param i row where finder pattern may be found\r
+ * @param j end of possible finder pattern in row\r
+ * @return true if a finder pattern candidate was found this time\r
+ */\r
private boolean handlePossibleCenter(int[] stateCount,\r
int i,\r
int j) {\r
// Re-cross check\r
centerJ = crossCheckHorizontal((int) centerJ, (int) centerI, stateCount[2]);\r
if (!Float.isNaN(centerJ)) {\r
- float estimatedModuleSize = (float) (stateCount[0] +\r
- stateCount[1] +\r
- stateCount[2] +\r
- stateCount[3] +\r
- stateCount[4]) / 7.0f;\r
+ float estimatedModuleSize =\r
+ (float) (stateCount[0] + stateCount[1] + stateCount[2] + stateCount[3] + stateCount[4]) / 7.0f;\r
boolean found = false;\r
int max = possibleCenters.size();\r
for (int index = 0; index < max; index++) {\r
}\r
}\r
if (!found) {\r
- possibleCenters.addElement(\r
- new FinderPattern(centerJ, centerI, estimatedModuleSize));\r
+ possibleCenters.addElement(new FinderPattern(centerJ, centerI, estimatedModuleSize));\r
}\r
return true;\r
}\r
return false;\r
}\r
\r
+ /**\r
+ * @return number of rows we could safely skip during scanning, based on the first\r
+ * two finder patterns that have been located. In some cases their position will\r
+ * allow us to infer that the third pattern must lie below a certain point farther\r
+ * down in the image.\r
+ */\r
private int findRowSkip() {\r
int max = possibleCenters.size();\r
if (max <= 1) {\r
return 0;\r
}\r
\r
+ /**\r
+ * @return true iff we have found at least 3 finder patterns that have been detected\r
+ * at least {@link #CENTER_QUORUM} times each\r
+ */\r
private boolean haveMulitplyConfirmedCenters() {\r
int count = 0;\r
int max = possibleCenters.size();\r
return false;\r
}\r
\r
+ /**\r
+ * @return the 3 best {@link FinderPattern}s from our list of candidates. The "best" are\r
+ * those that have been detected at least {@link #CENTER_QUORUM} times, and whose module\r
+ * size differs from the average among those patterns the least\r
+ * @throws ReaderException if 3 such finder patterns do not exist\r
+ */\r
private FinderPattern[] selectBestPatterns() throws ReaderException {\r
Collections.insertionSort(possibleCenters, new CenterComparator());\r
int size = 0;\r
}\r
averageModuleSize /= (float) size;\r
\r
- Collections.insertionSort(\r
- possibleCenters,\r
- new ClosestToAverageComparator(averageModuleSize));\r
+ // We don't have java.util.Collections in J2ME\r
+ Collections.insertionSort(possibleCenters, new ClosestToAverageComparator(averageModuleSize));\r
\r
- //return confirmedCenters.subList(0, 3).toArray(new FinderPattern[3]);\r
FinderPattern[] result = new FinderPattern[3];\r
for (int i = 0; i < 3; i++) {\r
result[i] = (FinderPattern) possibleCenters.elementAt(i);\r
return result;\r
}\r
\r
+ /**\r
+ * <p>Having found three "best" finder patterns we need to decide which is the top-left, top-right,\r
+ * bottom-left. We assume that the one closest to the other two is the top-left one; this is not\r
+ * strictly true (imagine extreme perspective distortion) but for the moment is a serviceable assumption.\r
+ * Lastly we sort top-right from bottom-left by figuring out orientation from vector cross products.</p>\r
+ *\r
+ * @param patterns three best {@link FinderPattern}s\r
+ * @return same {@link FinderPattern}s ordered bottom-left, top-left, top-right\r
+ */\r
private static FinderPattern[] orderBestPatterns(FinderPattern[] patterns) {\r
\r
// Find distances between pattern centers\r
FinderPattern topLeft;\r
FinderPattern topRight;\r
FinderPattern bottomLeft;\r
- // Assume one closest to other two is top left\r
+ // Assume one closest to other two is top left;\r
+ // topRight and bottomLeft will just be guesses below at first\r
if (bcDistance >= abDistance && bcDistance >= acDistance) {\r
topLeft = patterns[0];\r
- topRight = patterns[1]; // These two are guesses at the moment\r
+ topRight = patterns[1];\r
bottomLeft = patterns[2];\r
} else if (acDistance >= bcDistance && acDistance >= abDistance) {\r
topLeft = patterns[1];\r
return new FinderPattern[]{bottomLeft, topLeft, topRight};\r
}\r
\r
+ /**\r
+ * @return distance between two points\r
+ */\r
static float distance(ResultPoint pattern1, ResultPoint pattern2) {\r
float xDiff = pattern1.getX() - pattern2.getX();\r
float yDiff = pattern1.getY() - pattern2.getY();\r
return (float) Math.sqrt((double) (xDiff * xDiff + yDiff * yDiff));\r
}\r
\r
+ /**\r
+ * <p>Orders by {@link FinderPattern#getCount()}, descending.</p>\r
+ */\r
private static class CenterComparator implements Comparator {\r
public int compare(Object center1, Object center2) {\r
return ((FinderPattern) center2).getCount() - ((FinderPattern) center1).getCount();\r
}\r
}\r
\r
+ /**\r
+ * <p>Orders by variance from average module size, ascending.</p>\r
+ */\r
private static class ClosestToAverageComparator implements Comparator {\r
private float averageModuleSize;\r
\r
package com.google.zxing.qrcode.detector;
/**
+ * <p>Encapsulates information about finder patterns in an image, including the location of
+ * the three finder patterns, and their estimated module size.</p>
+ *
* @author srowen@google.com (Sean Owen)
*/
final class FinderPatternInfo {
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