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Improved bounds-checking and point-nudging logic in GridSampler. We should check more than endpoints.

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git-svn-id: https://zxing.googlecode.com/svn/trunk@317 59b500cc-1b3d-0410-9834-0bbf25fbcc57
This commit is contained in:
srowen 2008-03-26 17:01:13 +00:00
parent 4473c00147
commit 683a78256d
3 changed files with 53 additions and 24 deletions
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2
android/src/com/google/zxing/client/android/AndroidGraphicsGridSampler.java
View file

@ -68,7 +68,7 @@ public final class AndroidGraphicsGridSampler extends GridSampler {
transformMatrix.mapPoints(points);
// Quick check to see if points transformed to something inside the image;
// sufficent to check the endpoints
checkEndpoint(image, points);
checkAndNudgePoints(image, points);
for (int j = 0; j < max; j += 2) {
if (image.isBlack((int) points[j], (int) points[j + 1])) {
// Black(-ish) pixel

2
core/src/com/google/zxing/common/DefaultGridSampler.java
View file

@ -51,7 +51,7 @@ public final class DefaultGridSampler extends GridSampler {
transform.transformPoints(points);
// Quick check to see if points transformed to something inside the image;
// sufficent to check the endpoints
checkEndpoint(image, points);
checkAndNudgePoints(image, points);
for (int j = 0; j < max; j += 2) {
if (image.isBlack((int) points[j], (int) points[j + 1])) {
// Black(-ish) pixel

47
core/src/com/google/zxing/common/GridSampler.java
View file

@ -98,40 +98,69 @@ public abstract class GridSampler {
/**
* <p>Checks a set of points that have been transformed to sample points on an image against
* the image's dimensions to see if the endpoints are even within the image.
* This method actually only checks the endpoints since the points are assumed to lie
* on a line.</p>
* the image's dimensions to see if the point are even within the image.</p>
*
* <p>This method will actually "nudge" the endpoints back onto the image if they are found to be barely
* (less than 1 pixel) off the image. This accounts for imperfect detection of finder patterns in an image
* where the QR Code runs all the way to the image border.</p>
*
* <p>For efficiency, the method will check points from either end of the line until one is found
* to be within the image. Because the set of points are assumed to be linear, this is valid.</p>
*
* @param image image into which the points should map
* @param points actual points in x1,y1,...,xn,yn form
* @throws ReaderException if an endpoint is lies outside the image boundaries
*/
protected static void checkEndpoint(MonochromeBitmapSource image, float[] points) throws ReaderException {
protected static void checkAndNudgePoints(MonochromeBitmapSource image, float[] points) throws ReaderException {
int width = image.getWidth();
int height = image.getHeight();
checkOneEndpoint(points, 0, width, height);
checkOneEndpoint(points, points.length - 2, width, height);
}
private static void checkOneEndpoint(float[] points, int offset, int width, int height) throws ReaderException {
// Check and nudge points from start until we see some that are OK:
boolean nudged = true;
for (int offset = 0; offset < points.length && nudged; offset += 2) {
int x = (int) points[offset];
int y = (int) points[offset + 1];
if (x < -1 || x > width || y < -1 || y > height) {
throw new ReaderException("Transformed point out of bounds at " + x + ',' + y);
}
nudged = false;
if (x == -1) {
points[offset] = 0.0f;
nudged = true;
} else if (x == width) {
points[offset] = width - 1;
nudged = true;
}
if (y == -1) {
points[offset + 1] = 0.0f;
nudged = true;
} else if (y == height) {
points[offset + 1] = height - 1;
nudged = true;
}
}
// Check and nudge points from end:
nudged = true;
for (int offset = points.length - 2; offset >= 0 && nudged; offset -= 2) {
int x = (int) points[offset];
int y = (int) points[offset + 1];
if (x < -1 || x > width || y < -1 || y > height) {
throw new ReaderException("Transformed point out of bounds at " + x + ',' + y);
}
nudged = false;
if (x == -1) {
points[offset] = 0.0f;
nudged = true;
} else if (x == width) {
points[offset] = width - 1;
nudged = true;
}
if (y == -1) {
points[offset + 1] = 0.0f;
nudged = true;
} else if (y == height) {
points[offset + 1] = height - 1;
nudged = true;
}
}
}