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Changed the 2D histogram calculation to sample four rows spread across the image rather than taking a diagonal. We get a net increase of 63 blackbox tests with this change.

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git-svn-id: https://zxing.googlecode.com/svn/trunk@950 59b500cc-1b3d-0410-9834-0bbf25fbcc57
This commit is contained in:
dswitkin 2009-05-22 20:59:15 +00:00
parent 825d99786d
commit ec77a581d2
7 changed files with 36 additions and 32 deletions
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14
core/src/com/google/zxing/common/BaseMonochromeBitmapSource.java
View file

@ -59,15 +59,15 @@ public abstract class BaseMonochromeBitmapSource implements MonochromeBitmapSour
// Reuse the same int array each time
initLuminances();
luminances = getLuminanceRow(y, luminances);
int[] localLuminances = getLuminanceRow(y, luminances);
// If the current decoder calculated the blackPoint based on one row, assume we're trying to
// decode a 1D barcode, and apply some sharpening.
if (lastMethod.equals(BlackPointEstimationMethod.ROW_SAMPLING)) {
int left = luminances[startX];
int center = luminances[startX + 1];
int left = localLuminances[startX];
int center = localLuminances[startX + 1];
for (int x = 1; x < getWidth - 1; x++) {
int right = luminances[startX + x + 1];
int right = localLuminances[startX + x + 1];
// Simple -1 4 -1 box filter with a weight of 2
int luminance = ((center << 2) - left - right) >> 1;
if (luminance < blackPoint) {
@ -78,7 +78,7 @@ public abstract class BaseMonochromeBitmapSource implements MonochromeBitmapSour
}
} else {
for (int x = 0; x < getWidth; x++) {
if (luminances[startX + x] < blackPoint) {
if (localLuminances[startX + x] < blackPoint) {
row.set(x);
}
}
@ -95,11 +95,11 @@ public abstract class BaseMonochromeBitmapSource implements MonochromeBitmapSour
// Reuse the same int array each time
initLuminances();
luminances = getLuminanceColumn(x, luminances);
int[] localLuminances = getLuminanceColumn(x, luminances);
// We don't handle "row sampling" specially here
for (int y = 0; y < getHeight; y++) {
if (luminances[startY + y] < blackPoint) {
if (localLuminances[startY + y] < blackPoint) {
column.set(y);
}
}

24
core/src/com/google/zxing/common/BlackPointEstimator.java
View file

@ -25,8 +25,7 @@ import com.google.zxing.ReaderException;
* which is the best line between "white" and "black" in a grayscale image.</p>
*
* <p>For an interesting discussion of this issue, see
* <a href="http://webdiis.unizar.es/~neira/12082/thresholding.pdf">http://webdiis.unizar.es/~neira/12082/thresholding.pdf</a>.
* </p>
* <a href="http://webdiis.unizar.es/~neira/12082/thresholding.pdf">this paper</a>.</p>
*
* NOTE: This class is not threadsafe.
*
@ -74,21 +73,26 @@ public final class BlackPointEstimator {
initArrays(width);
if (method.equals(BlackPointEstimationMethod.TWO_D_SAMPLING)) {
int minDimension = width < height ? width : height;
int startX = (width - minDimension) >> 1;
int startY = (height - minDimension) >> 1;
for (int n = 0; n < minDimension; n++) {
int luminance = source.getLuminance(startX + n, startY + n);
histogram[luminance >> LUMINANCE_SHIFT]++;
// We used to sample a diagonal in the 2D case, but it missed a lot of pixels, and it required
// n calls to getLuminance(). We had a net improvement of 63 blackbox tests decoded by
// sampling several rows from the middle of the image, using getLuminanceRow(). We read more
// pixels total, but with fewer function calls, and more continguous memory.
for (int y = 1; y < 5; y++) {
int row = height * y / 5;
int[] localLuminances = source.getLuminanceRow(row, luminances);
int right = width * 4 / 5;
for (int x = width / 5; x < right; x++) {
histogram[localLuminances[x] >> LUMINANCE_SHIFT]++;
}
}
} else if (method.equals(BlackPointEstimationMethod.ROW_SAMPLING)) {
if (argument < 0 || argument >= height) {
throw new IllegalArgumentException("Row is not within the image: " + argument);
}
luminances = source.getLuminanceRow(argument, luminances);
int[] localLuminances = source.getLuminanceRow(argument, luminances);
for (int x = 0; x < width; x++) {
histogram[luminances[x] >> LUMINANCE_SHIFT]++;
histogram[localLuminances[x] >> LUMINANCE_SHIFT]++;
}
} else {
throw new IllegalArgumentException("Unknown method");

2
core/test/src/com/google/zxing/datamatrix/DataMatrixBlackBox2TestCase.java
View file

@ -27,7 +27,7 @@ public final class DataMatrixBlackBox2TestCase extends AbstractBlackBoxTestCase
public DataMatrixBlackBox2TestCase() {
// TODO use MultiFormatReader here once Data Matrix decoder is done
super("test/data/blackbox/datamatrix-2", new DataMatrixReader(), BarcodeFormat.DATAMATRIX);
addTest(3, 3, 0.0f);
addTest(2, 2, 0.0f);
addTest(1, 1, 90.0f);
addTest(4, 4, 180.0f);
addTest(3, 3, 270.0f);

6
core/test/src/com/google/zxing/qrcode/QRCodeBlackBox1TestCase.java
View file

@ -27,9 +27,9 @@ public final class QRCodeBlackBox1TestCase extends AbstractBlackBoxTestCase {
public QRCodeBlackBox1TestCase() {
super("test/data/blackbox/qrcode-1", new MultiFormatReader(), BarcodeFormat.QR_CODE);
addTest(18, 18, 0.0f);
addTest(14, 14, 90.0f);
addTest(18, 18, 180.0f);
addTest(19, 19, 0.0f);
addTest(15, 15, 90.0f);
addTest(16, 16, 180.0f);
addTest(13, 14, 270.0f);
}

6
core/test/src/com/google/zxing/qrcode/QRCodeBlackBox2TestCase.java
View file

@ -27,10 +27,10 @@ public final class QRCodeBlackBox2TestCase extends AbstractBlackBoxTestCase {
public QRCodeBlackBox2TestCase() {
super("test/data/blackbox/qrcode-2", new MultiFormatReader(), BarcodeFormat.QR_CODE);
addTest(22, 22, 0.0f);
addTest(18, 18, 90.0f);
addTest(24, 24, 0.0f);
addTest(21, 21, 90.0f);
addTest(22, 22, 180.0f);
addTest(17, 17, 270.0f);
addTest(17, 18, 270.0f);
}
}

8
core/test/src/com/google/zxing/qrcode/QRCodeBlackBox3TestCase.java
View file

@ -27,10 +27,10 @@ public final class QRCodeBlackBox3TestCase extends AbstractBlackBoxTestCase {
public QRCodeBlackBox3TestCase() {
super("test/data/blackbox/qrcode-3", new MultiFormatReader(), BarcodeFormat.QR_CODE);
addTest(29, 29, 0.0f);
addTest(26, 26, 90.0f);
addTest(30, 30, 180.0f);
addTest(29, 29, 270.0f);
addTest(33, 33, 0.0f);
addTest(33, 33, 90.0f);
addTest(32, 32, 180.0f);
addTest(34, 34, 270.0f);
}
}

8
core/test/src/com/google/zxing/qrcode/QRCodeBlackBox4TestCase.java
View file

@ -29,10 +29,10 @@ public final class QRCodeBlackBox4TestCase extends AbstractBlackBoxTestCase {
public QRCodeBlackBox4TestCase() {
super("test/data/blackbox/qrcode-4", new MultiFormatReader(), BarcodeFormat.QR_CODE);
addTest(33, 33, 0.0f);
addTest(33, 33, 90.0f);
addTest(32, 32, 180.0f);
addTest(32, 32, 270.0f);
addTest(34, 34, 0.0f);
addTest(36, 36, 90.0f);
addTest(35, 35, 180.0f);
addTest(34, 34, 270.0f);
}
}