I noticed that the codeword coordinates in PDF 417 barcodes were a few pixels off if there was skew or rotation in the image. I added a simple method to correct the vertical component of these points, and the units tests went from 8/23 to 11/23.

git-svn-id: https://zxing.googlecode.com/svn/trunk@1015 59b500cc-1b3d-0410-9834-0bbf25fbcc57
This commit is contained in:
dswitkin 2009-07-02 20:07:09 +00:00
parent 0944a2bb18
commit b238cb7828
2 changed files with 52 additions and 3 deletions

View file

@ -30,11 +30,13 @@ import java.util.Hashtable;
* PDF417 Code is rotated or skewed, or partially obscured.</p>
*
* @author SITA Lab (kevin.osullivan@sita.aero)
* @author dswitkin@google.com (Daniel Switkin)
*/
public final class Detector {
public static final int MAX_AVG_VARIANCE = (int) ((1 << 8) * 0.42f);
public static final int MAX_INDIVIDUAL_VARIANCE = (int) ((1 << 8) * 0.8f);
private static final int MAX_AVG_VARIANCE = (int) ((1 << 8) * 0.42f);
private static final int MAX_INDIVIDUAL_VARIANCE = (int) ((1 << 8) * 0.8f);
private static final int SKEW_THRESHOLD = 2;
// B S B S B S B S Bar/Space pattern
// 11111111 0 1 0 1 0 1 000
@ -90,6 +92,7 @@ public final class Detector {
throw ReaderException.getInstance();
}
correctCodeWordVertices(vertices);
int dimension = computeDimension(vertices[4], vertices[6],
vertices[5], vertices[7], moduleWidth);
@ -262,6 +265,52 @@ public final class Detector {
return found ? result : null;
}
/**
* Because we scan horizontally to detect the start and stop patterns, the vertical component of
* the codeword coordinates will be slightly wrong if there is any skew or rotation in the image.
* This method moves those points back onto the edges of the theoretically perfect bounding
* quadrilateral if needed.
*
* FIXME: Make this work for 180 degree rotation.
*
* @param vertices The eight vertices located by findVertices().
*/
private static void correctCodeWordVertices(ResultPoint[] vertices) {
float skew = vertices[4].getY() - vertices[6].getY();
if (skew > SKEW_THRESHOLD) {
// Fix v4
float length = vertices[4].getX() - vertices[0].getX();
float deltax = vertices[6].getX() - vertices[0].getX();
float deltay = vertices[6].getY() - vertices[0].getY();
float correction = length * deltay / deltax;
vertices[4] = new ResultPoint(vertices[4].getX(), vertices[4].getY() + correction);
} else if (-skew > SKEW_THRESHOLD) {
// Fix v6
float length = vertices[2].getX() - vertices[6].getX();
float deltax = vertices[2].getX() - vertices[4].getX();
float deltay = vertices[2].getY() - vertices[4].getY();
float correction = length * deltay / deltax;
vertices[6] = new ResultPoint(vertices[6].getX(), vertices[6].getY() - correction);
}
skew = vertices[7].getY() - vertices[5].getY();
if (skew > SKEW_THRESHOLD) {
// Fix v5
float length = vertices[5].getX() - vertices[1].getX();
float deltax = vertices[7].getX() - vertices[1].getX();
float deltay = vertices[7].getY() - vertices[1].getY();
float correction = length * deltay / deltax;
vertices[5] = new ResultPoint(vertices[5].getX(), vertices[5].getY() + correction);
} else if (-skew > SKEW_THRESHOLD) {
// Fix v7
float length = vertices[3].getX() - vertices[7].getX();
float deltax = vertices[3].getX() - vertices[5].getX();
float deltay = vertices[3].getY() - vertices[5].getY();
float correction = length * deltay / deltax;
vertices[7] = new ResultPoint(vertices[7].getX(), vertices[7].getY() - correction);
}
}
/**
* <p>Estimates module size (pixels in a module) based on the Start and End
* finder patterns.</p>

View file

@ -33,7 +33,7 @@ public final class PDF417BlackBox2TestCase extends AbstractBlackBoxTestCase {
public PDF417BlackBox2TestCase() {
super("test/data/blackbox/pdf417-2", new MultiFormatReader(), BarcodeFormat.PDF417);
addTest(8, 8, 0.0f);
addTest(11, 11, 0.0f);
addTest(9, 9, 180.0f);
}