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Switch to integer math in a critical QR Code detector method for speed and tweak a few things before I start investigating this method and the infamous "270 issue"

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git-svn-id: https://zxing.googlecode.com/svn/trunk@485 59b500cc-1b3d-0410-9834-0bbf25fbcc57
This commit is contained in:
srowen 2008-06-26 22:14:53 +00:00
parent c9018b1bd2
commit 621a9f25e9
1 changed files with 14 additions and 12 deletions
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26
core/src/com/google/zxing/qrcode/detector/FinderPatternFinder.java
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@ -40,6 +40,7 @@ final class FinderPatternFinder {
private static final int CENTER_QUORUM = 2; private static final int CENTER_QUORUM = 2;
private static final int MIN_SKIP = 3; // 1 pixel/module times 3 modules/center private static final int MIN_SKIP = 3; // 1 pixel/module times 3 modules/center
private static final int MAX_MODULES = 57; // support up to version 10 for mobile clients private static final int MAX_MODULES = 57; // support up to version 10 for mobile clients
private static final int INTEGER_MATH_SHIFT = 8;
private final MonochromeBitmapSource image; private final MonochromeBitmapSource image;
private final Vector possibleCenters; private final Vector possibleCenters;
@ -61,8 +62,6 @@ final class FinderPatternFinder {
int maxJ = image.getWidth(); int maxJ = image.getWidth();
// We are looking for black/white/black/white/black modules in // We are looking for black/white/black/white/black modules in
// 1:1:3:1:1 ratio; this tracks the number of such modules seen so far // 1:1:3:1:1 ratio; this tracks the number of such modules seen so far
int[] stateCount = new int[5];
boolean done = false;
// Let's assume that the maximum version QR Code we support takes up 1/4 the height of the // Let's assume that the maximum version QR Code we support takes up 1/4 the height of the
// image, and then account for the center being 3 modules in size. This gives the smallest // image, and then account for the center being 3 modules in size. This gives the smallest
@ -73,6 +72,8 @@ final class FinderPatternFinder {
iSkip = MIN_SKIP; iSkip = MIN_SKIP;
} }
boolean done = false;
int[] stateCount = new int[5];
for (int i = iSkip - 1; i < maxI && !done; i += iSkip) { for (int i = iSkip - 1; i < maxI && !done; i += iSkip) {
// Get a row of black/white values // Get a row of black/white values
BitArray blackRow = image.getBlackRow(i, null, 0, maxJ); BitArray blackRow = image.getBlackRow(i, null, 0, maxJ);
@ -171,28 +172,29 @@ final class FinderPatternFinder {
/** /**
* @param stateCount count of black/white/black/white/black pixels just read * @param stateCount count of black/white/black/white/black pixels just read
* @return true iff the proportions of the counts is close enough to the 1/13/1/1 ratios * @return true iff the proportions of the counts is close enough to the 1/1/3/1/1 ratios
* used by finder patterns to be considered a match * used by finder patterns to be considered a match
*/ */
private static boolean foundPatternCross(int[] stateCount) { private static boolean foundPatternCross(int[] stateCount) {
int totalModuleSize = 0; int totalModuleSize = 0;
for (int i = 0; i < 5; i++) { for (int i = 0; i < 5; i++) {
if (stateCount[i] == 0) { int count = stateCount[i];
if (count == 0) {
return false; return false;
} }
totalModuleSize += stateCount[i]; totalModuleSize += count;
} }
if (totalModuleSize < 7) { if (totalModuleSize < 7) {
return false; return false;
} }
float moduleSize = (float) totalModuleSize / 7.0f; int moduleSize = (totalModuleSize << INTEGER_MATH_SHIFT) / 7;
float maxVariance = moduleSize / 2.0f; int maxVariance = moduleSize / 2;
// Allow less than 50% variance from 1-1-3-1-1 proportions // Allow less than 50% variance from 1-1-3-1-1 proportions
return Math.abs(moduleSize - stateCount[0]) < maxVariance && return Math.abs(moduleSize - (stateCount[0] << INTEGER_MATH_SHIFT)) < maxVariance &&
Math.abs(moduleSize - stateCount[1]) < maxVariance && Math.abs(moduleSize - (stateCount[1] << INTEGER_MATH_SHIFT)) < maxVariance &&
Math.abs(3.0f * moduleSize - stateCount[2]) < 3.0f * maxVariance && Math.abs(3 * moduleSize - (stateCount[2] << INTEGER_MATH_SHIFT)) < 3 * maxVariance &&
Math.abs(moduleSize - stateCount[3]) < maxVariance && Math.abs(moduleSize - (stateCount[3] << INTEGER_MATH_SHIFT)) < maxVariance &&
Math.abs(moduleSize - stateCount[4]) < maxVariance; Math.abs(moduleSize - (stateCount[4] << INTEGER_MATH_SHIFT)) < maxVariance;
} }
/** /**