/**
* 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.application.food.zxing.pdf417.PDF417Reader#extractPureBits(com.application.food.zxing.common.BitMatrix)
* @see
* com.application.food.zxing.datamatrix.DataMatrixReader#extractPureBits(com.application.food.zxing.common.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();
}
float moduleSize = moduleSize(leftTopBlack, image);
int top = leftTopBlack[1];
int bottom = rightBottomBlack[1];
int left = leftTopBlack[0];
int right = rightBottomBlack[0];
if (bottom - top != right - left) {
// Special case, where bottom-right module wasn't black so we found something else in the last
// row
// Assume it's a square, so use height as the width
right = left + (bottom - top);
}
int matrixWidth = Math.round((right - left + 1) / moduleSize);
int matrixHeight = Math.round((bottom - top + 1) / moduleSize);
if (matrixWidth <= 0 || matrixHeight <= 0) {
throw NotFoundException.getNotFoundInstance();
}
if (matrixHeight != matrixWidth) {
// Only possibly decode square regions
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 = Math.round(moduleSize / 2.0f);
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 + (int) (y * moduleSize);
for (int x = 0; x < matrixWidth; x++) {
if (image.get(left + (int) (x * moduleSize), iOffset)) {
bits.set(x, y);
}
}
}
return bits;
}
protected static int parseFinderValue(int[] counters, int[][] finderPatterns)
throws NotFoundException {
for (int value = 0; value < finderPatterns.length; value++) {
if (patternMatchVariance(counters, finderPatterns[value], MAX_INDIVIDUAL_VARIANCE)
< MAX_AVG_VARIANCE) {
return value;
}
}
throw NotFoundException.getNotFoundInstance();
}
/**
* @return the 3 best {@link FinderPattern}s from our list of candidates. The "best" are those
* that have been detected at least {@link #CENTER_QUORUM} times, and whose module size
* differs from the average among those patterns the least
* @throws com.application.food.zxing.NotFoundException if 3 such finder patterns do not exist
*/
private FinderPattern[] selectBestPatterns() throws NotFoundException {
int startSize = possibleCenters.size();
if (startSize < 3) {
// Couldn't find enough finder patterns
throw NotFoundException.getNotFoundInstance();
}
// Filter outlier possibilities whose module size is too different
if (startSize > 3) {
// But we can only afford to do so if we have at least 4 possibilities to choose from
float totalModuleSize = 0.0f;
float square = 0.0f;
for (FinderPattern center : possibleCenters) {
float size = center.getEstimatedModuleSize();
totalModuleSize += size;
square += size * size;
}
float average = totalModuleSize / (float) startSize;
float stdDev = (float) Math.sqrt(square / startSize - average * average);
Collections.sort(possibleCenters, new FurthestFromAverageComparator(average));
float limit = Math.max(0.2f * average, stdDev);
for (int i = 0; i < possibleCenters.size() && possibleCenters.size() > 3; i++) {
FinderPattern pattern = possibleCenters.get(i);
if (Math.abs(pattern.getEstimatedModuleSize() - average) > limit) {
possibleCenters.remove(i);
i--;
}
}
}
if (possibleCenters.size() > 3) {
// Throw away all but those first size candidate points we found.
float totalModuleSize = 0.0f;
for (FinderPattern possibleCenter : possibleCenters) {
totalModuleSize += possibleCenter.getEstimatedModuleSize();
}
float average = totalModuleSize / (float) possibleCenters.size();
Collections.sort(possibleCenters, new CenterComparator(average));
possibleCenters.subList(3, possibleCenters.size()).clear();
}
return new FinderPattern[] {
possibleCenters.get(0), possibleCenters.get(1), possibleCenters.get(2)
};
}
private static float moduleSize(int[] leftTopBlack, BitMatrix image) throws NotFoundException {
int height = image.getHeight();
int width = image.getWidth();
int x = leftTopBlack[0];
int y = leftTopBlack[1];
boolean inBlack = true;
int transitions = 0;
while (x < width && y < height) {
if (inBlack != image.get(x, y)) {
if (++transitions == 5) {
break;
}
inBlack = !inBlack;
}
x++;
y++;
}
if (x == width || y == height) {
throw NotFoundException.getNotFoundInstance();
}
return (x - leftTopBlack[0]) / 7.0f;
}
