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Factor out and clarify cross product computation and its use, so it can be reused elsewhere.

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git-svn-id: https://zxing.googlecode.com/svn/trunk@527 59b500cc-1b3d-0410-9834-0bbf25fbcc57
This commit is contained in:
srowen 2008-07-23 18:54:35 +00:00
parent cebac631ac
commit a43e928575
1 changed files with 13 additions and 2 deletions
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15
core/src/com/google/zxing/common/GenericResultPoint.java
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@ -92,8 +92,10 @@ public final class GenericResultPoint implements ResultPoint {
} }
// Use cross product to figure out whether A and C are correct or flipped. // Use cross product to figure out whether A and C are correct or flipped.
if ((pointC.getY() - pointB.getY()) * (pointA.getX() - pointB.getX()) > // This asks whether BC x BA has a positive z component, which is the arrangement
(pointC.getX() - pointB.getX()) * (pointA.getY() - pointB.getY())) { // we want for A, B, C. If it's negative, then we've got it flipped around and
// should swap A and C.
if (crossProductZ(pointA, pointB, pointC) < 0.0f) {
ResultPoint temp = pointA; ResultPoint temp = pointA;
pointA = pointC; pointA = pointC;
pointC = temp; pointC = temp;
@ -114,4 +116,13 @@ public final class GenericResultPoint implements ResultPoint {
return (float) Math.sqrt((double) (xDiff * xDiff + yDiff * yDiff)); return (float) Math.sqrt((double) (xDiff * xDiff + yDiff * yDiff));
} }
/**
* Returns the z component of the cross product between vectors BC and BA.
*/
public static float crossProductZ(ResultPoint pointA, ResultPoint pointB, ResultPoint pointC) {
float bX = pointB.getX();
float bY = pointB.getY();
return ((pointC.getX() - bX) * (pointA.getY() - bY)) - ((pointC.getY() - bY) * (pointA.getX() - bX));
}
} }