Open Source QR Code Library

I rewrite the findLineAcross(), checkPattern(), findLineCross() like the following:

/*
* 位置要素検出パターンを検出するために、(暗:明:暗:明:暗)=(1:1:3:1:1)の
* パターンに一致する区間を線分として抽出する。
* 注意：位置要素パターンを横切らない部分が抽出されることもある
*/
static Line[] findLineAcross(boolean[][] image) {
final boolean[] nextSectionElement = {false,
QRCodeImageReader.POINT_LIGHT,
QRCodeImageReader.POINT_DARK,
QRCodeImageReader.POINT_LIGHT,
QRCodeImageReader.POINT_DARK,
QRCodeImageReader.POINT_LIGHT};

int imageWidth = image.length;
int imageHeight = image[0].length;
int currentX, currentY;

Vector lineAcross = new Vector();

// 直近の、同じ色で連続した要素の長さ
int[] lengthBuffer = new int[5];
int bufferPointer;
int nsection;
boolean currentElement, lastElement;

// Read horizontal
for (currentY = 0; currentY < imageHeight; currentY++) {

lengthBuffer[bufferPointer = 0] = 0;
nsection = 1;
lastElement = QRCodeImageReader.POINT_LIGHT;

for (currentX = 0; currentX < imageWidth; currentX++) {
currentElement = image[currentX][currentY];
if (currentElement == lastElement) { //前回の要素と同じ
lengthBuffer[bufferPointer]++;
} else { //前回の要素と違う
if (currentElement == nextSectionElement[nsection]) {
while (nsection > 2) {
// Check with current secsions.
if (checkPattern(lengthBuffer, bufferPointer, nsection)) {
// The rate of the secsions' length is OK.
if (nsection == 5) {
// Add this pattern into lineAcross.
int x1, y1, x2, y2;
// パターン候補の両端のx座標を求める
// 左端は現在の要素のx座標とバッファの長さの和から算出
x1 = currentX;
for (int j = 0; j < 5; j++) {
x1 -= lengthBuffer[j];
}
x2 = currentX - 1; // 右端は直前の要素のx座標
y1 = y2 = currentY;
lineAcross.addElement(new Line(x1, y1, x2, y2));

// Continue checking, so that we may reduce the nsection.
nsection -= 2;
} else {
// The rate is OK, but the number of the sections is not 5,
// so read in the next section.
break;
}
} else {
// The rate is not OK, so continue checking to cut
// out the unnecessary sections.
nsection -= 2;
}
} // of while
} else {
// The nsection == 1, but its color is white, so it can be the section no.1 in the 5 sections.
nsection--;
}
nsection++;
bufferPointer = (bufferPointer + 1) % 5;
lengthBuffer[bufferPointer] = 1;
lastElement = !lastElement;
}
}
}

// Read vertical
for (currentX = 0; currentX < imageWidth; currentX++) {

lengthBuffer[bufferPointer = 0] = 0;
nsection = 1;
lastElement = QRCodeImageReader.POINT_LIGHT;

for (currentY = 0; currentY < imageHeight; currentY++) {
currentElement = image[currentX][currentY];
if (currentElement == lastElement) { //前回の要素と同じ
lengthBuffer[bufferPointer]++;
} else { //前回の要素と違う
if (currentElement == nextSectionElement[nsection]) {
while (nsection > 2) {
// Check with current secsions.
if (checkPattern(lengthBuffer, bufferPointer, nsection)) {
// The rate of the secsions' length is OK.
if (nsection == 5) {
// Add this pattern into lineAcross.
int x1, y1, x2, y2;
x1 = x2 = currentX;
// パターン候補の両端のy座標を求める
// 左端は現在の要素のy座標とバッファの長さの和から算出
y1 = currentY;
for (int j = 0; j < 5; j++) {
y1 -= lengthBuffer[j];
}
y2 = currentY - 1; // 右端は直前の要素のy座標
lineAcross.addElement(new Line(x1, y1, x2, y2));

// Continue checking, so that we may reduce the nsection.
nsection -= 2;
} else {
// The rate is OK, but the number of the sections is not 5,
// so read in the next section.
break;
}
} else {
// The rate is not OK, so continue checking to cut
// out the unnecessary sections.
nsection -= 2;
}
} // of while
} else {
// The nsection == 1, but its color is white, so it can be the section no.1 in the 5 sections.
nsection--;
}
nsection++;
bufferPointer = (bufferPointer + 1) % 5;
lengthBuffer[bufferPointer] = 1;
lastElement = !lastElement;
}
}
}

Line[] foundLines = new Line[lineAcross.size()];

for (int i = 0; i < foundLines.length; i++)
foundLines[i] = (Line) lineAcross.elementAt(i);

return foundLines;
}

static boolean checkPattern(int[] buffer, int pointer, int nsection) {
final int[] modelRatio = {1, 1, 3, 1, 1};
final int[] modelPart = {1, 2, 5, 6, 7};

int nsection_1 = nsection - 1;
int i;
int baselength = 0;
for (i = 0; i < nsection; i++) {
baselength += buffer[(pointer + 5 - nsection_1 + i) % 5];
}
baselength <<= QRCodeImageReader.DECIMAL_POINT; //丸め誤差を減らすために4098倍する
baselength /= modelPart[nsection_1];

for (i = 0; i < nsection; i++) {
int leastlength = baselength * modelRatio[i] - baselength / 2;
int mostlength = baselength * modelRatio[i] + baselength / 2;

//試験的に条件を甘くする
leastlength -= baselength / 8;
mostlength += baselength / 8;

int targetlength = buffer[(pointer + 5 - nsection_1 + i) % 5] << QRCodeImageReader.DECIMAL_POINT;
if (targetlength < leastlength || targetlength > mostlength) {
return false;
}
}
return true;
}

/**
* Scan lines received from findLIneAcross() and detemine where are center(s) of three Finder Patterns.
* @param lineAcross
* @return The center lines (in normal, be 6 lines).
*/
static Line[] findLineCross(Line[] lineAcross) {
int numLineCandidate = lineAcross.length;
int numLineCandidate_1 = numLineCandidate - 1;
int[] lineNeighborIndex = new int[numLineCandidate];
int numLineNeighborIndex;
int[] crossLineIndex = new int[numLineCandidate];
int numCrossLineIndex = 0;
boolean[] removedOfIndex = new boolean[numLineCandidate];

for (int i = 0; i < numLineCandidate_1; i++) {
if (!removedOfIndex[i]) {
// Start finding pattern from line[i].

// Start the list of neighbor lines.
numLineNeighborIndex = 0;
lineNeighborIndex[numLineNeighborIndex++] = i;
int lastNeighborIndex = i;

// Search for the next lines.
for (int j = i + 1; j < numLineCandidate; j++) {
if (!removedOfIndex[j]) {
if (Line.isNeighbor(lineAcross[lastNeighborIndex], lineAcross[j])) {
// Add line[j] to the list of neighbor lines.
lastNeighborIndex = lineNeighborIndex[numLineNeighborIndex++] = j;

// Check if reach to the last line of lineAcross.
if (j == numLineCandidate_1
&& numLineNeighborIndex * 5 > lineAcross[lastNeighborIndex].getLength()) {
// Get the center line of this neighbor lines.
crossLineIndex[numCrossLineIndex++] = lineNeighborIndex[numLineNeighborIndex / 2];

// Mark all neighbor lines are removed.
for (int k = 0; k < numLineNeighborIndex; k++) {
removedOfIndex[lineNeighborIndex[k]] = true;
}
}
}
// Terminate comparision if there are no possibility for found neighbor lines.
else if (j == numLineCandidate_1
||cantNeighbor(lineAcross[lastNeighborIndex], lineAcross[j])) {
// Determine lines across Finder Patterns when number of neightbor lines are
// bigger than 1/6 length of theirselves.
if (numLineNeighborIndex * 6 > lineAcross[lastNeighborIndex].getLength()) {
// Get the center line of this neighbor lines.
crossLineIndex[numCrossLineIndex++] = lineNeighborIndex[numLineNeighborIndex / 2];

// Mark all neighbor lines are removed.
for (int k = 0; k < numLineNeighborIndex; k++) {
removedOfIndex[lineNeighborIndex[k]] = true;
}
}
break;
}
}
}
}
}

Line[] foundLines = new Line[numCrossLineIndex];
for (int i = 0; i < numCrossLineIndex; i++) {
Line line = lineAcross[crossLineIndex[i]];
foundLines[i] = new Line(line.x1, line.y1, line.x2, line.y2);
}
return foundLines;
}

> This approach is based on "Near place of the finderPattern has many crossLines" hypothesis.

Sorry, I mistyped. and please let me correct.

This approach is based on "Near place of the finderPattern has many across lines" hypothesis.