src/core/qrcode/detector/FinderPatternFinder.ts
/*
* Copyright 2007 ZXing authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*namespace com.google.zxing.qrcode.detector {*/
import DecodeHintType from '../../DecodeHintType';
import ResultPoint from '../../ResultPoint';
import ResultPointCallback from '../../ResultPointCallback';
import BitMatrix from '../../common/BitMatrix';
import FinderPattern from './FinderPattern';
import FinderPatternInfo from './FinderPatternInfo';
import NotFoundException from '../../NotFoundException';
import { float } from '../../../customTypings';
/*import java.io.Serializable;*/
/*import java.util.ArrayList;*/
/*import java.util.Collections;*/
/*import java.util.Comparator;*/
/*import java.util.List;*/
/*import java.util.Map;*/
/**
* <p>This class attempts to find finder patterns in a QR Code. Finder patterns are the square
* markers at three corners of a QR Code.</p>
*
* <p>This class is thread-safe but not reentrant. Each thread must allocate its own object.
*
* @author Sean Owen
*/
export default class FinderPatternFinder {
private static CENTER_QUORUM = 2;
protected static MIN_SKIP = 3; // 1 pixel/module times 3 modules/center
protected static MAX_MODULES = 57; // support up to version 10 for mobile clients
private possibleCenters: FinderPattern[];
private hasSkipped: boolean;
private crossCheckStateCount: Int32Array;
/**
* <p>Creates a finder that will search the image for three finder patterns.</p>
*
* @param image image to search
*/
// public constructor(image: BitMatrix) {
// this(image, null)
// }
public constructor(private image: BitMatrix, private resultPointCallback: ResultPointCallback) {
this.possibleCenters = [];
this.crossCheckStateCount = new Int32Array(5);
this.resultPointCallback = resultPointCallback;
}
protected getImage(): BitMatrix {
return this.image;
}
protected getPossibleCenters(): FinderPattern[] {
return this.possibleCenters;
}
public find(hints: Map<DecodeHintType, any>): FinderPatternInfo /*throws NotFoundException */ {
const tryHarder: boolean = (hints !== null && hints !== undefined) && undefined !== hints.get(DecodeHintType.TRY_HARDER);
const pureBarcode: boolean = (hints !== null && hints !== undefined) && undefined !== hints.get(DecodeHintType.PURE_BARCODE);
const image = this.image;
const maxI = image.getHeight();
const maxJ = image.getWidth();
// 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
// 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
// number of pixels the center could be, so skip this often. When trying harder, look for all
// QR versions regardless of how dense they are.
let iSkip = Math.floor((3 * maxI) / (4 * FinderPatternFinder.MAX_MODULES));
if (iSkip < FinderPatternFinder.MIN_SKIP || tryHarder) {
iSkip = FinderPatternFinder.MIN_SKIP;
}
let done: boolean = false;
const stateCount = new Int32Array(5);
for (let i = iSkip - 1; i < maxI && !done; i += iSkip) {
// Get a row of black/white values
stateCount[0] = 0;
stateCount[1] = 0;
stateCount[2] = 0;
stateCount[3] = 0;
stateCount[4] = 0;
let currentState = 0;
for (let j = 0; j < maxJ; j++) {
if (image.get(j, i)) {
// Black pixel
if ((currentState & 1) === 1) { // Counting white pixels
currentState++;
}
stateCount[currentState]++;
} else { // White pixel
if ((currentState & 1) === 0) { // Counting black pixels
if (currentState === 4) { // A winner?
if (FinderPatternFinder.foundPatternCross(stateCount)) { // Yes
const confirmed: boolean = this.handlePossibleCenter(stateCount, i, j, pureBarcode);
if (confirmed === true) {
// Start examining every other line. Checking each line turned out to be too
// expensive and didn't improve performance.
iSkip = 2;
if (this.hasSkipped === true) {
done = this.haveMultiplyConfirmedCenters();
} else {
const rowSkip = this.findRowSkip();
if (rowSkip > stateCount[2]) {
// Skip rows between row of lower confirmed center
// and top of presumed third confirmed center
// but back up a bit to get a full chance of detecting
// it, entire width of center of finder pattern
// Skip by rowSkip, but back off by stateCount[2] (size of last center
// of pattern we saw) to be conservative, and also back off by iSkip which
// is about to be re-added
i += rowSkip - stateCount[2] - iSkip;
j = maxJ - 1;
}
}
} else {
stateCount[0] = stateCount[2];
stateCount[1] = stateCount[3];
stateCount[2] = stateCount[4];
stateCount[3] = 1;
stateCount[4] = 0;
currentState = 3;
continue;
}
// Clear state to start looking again
currentState = 0;
stateCount[0] = 0;
stateCount[1] = 0;
stateCount[2] = 0;
stateCount[3] = 0;
stateCount[4] = 0;
} else { // No, shift counts back by two
stateCount[0] = stateCount[2];
stateCount[1] = stateCount[3];
stateCount[2] = stateCount[4];
stateCount[3] = 1;
stateCount[4] = 0;
currentState = 3;
}
} else {
stateCount[++currentState]++;
}
} else { // Counting white pixels
stateCount[currentState]++;
}
}
}
if (FinderPatternFinder.foundPatternCross(stateCount)) {
const confirmed: boolean = this.handlePossibleCenter(stateCount, i, maxJ, pureBarcode);
if (confirmed === true) {
iSkip = stateCount[0];
if (this.hasSkipped) {
// Found a third one
done = this.haveMultiplyConfirmedCenters();
}
}
}
}
const patternInfo: FinderPattern[] = this.selectBestPatterns();
ResultPoint.orderBestPatterns(patternInfo);
return new FinderPatternInfo(patternInfo);
}
/**
* Given a count of black/white/black/white/black pixels just seen and an end position,
* figures the location of the center of this run.
*/
private static centerFromEnd(stateCount: Int32Array, end: number /*int*/): number/*float*/ {
return (end - stateCount[4] - stateCount[3]) - stateCount[2] / 2.0;
}
/**
* @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 1/1/3/1/1 ratios
* used by finder patterns to be considered a match
*/
protected static foundPatternCross(stateCount: Int32Array): boolean {
let totalModuleSize = 0;
for (let i = 0; i < 5; i++) {
const count = stateCount[i];
if (count === 0) {
return false;
}
totalModuleSize += count;
}
if (totalModuleSize < 7) {
return false;
}
const moduleSize: number /*float*/ = totalModuleSize / 7.0;
const maxVariance: number /*float*/ = moduleSize / 2.0;
// Allow less than 50% variance from 1-1-3-1-1 proportions
return Math.abs(moduleSize - stateCount[0]) < maxVariance &&
Math.abs(moduleSize - stateCount[1]) < maxVariance &&
Math.abs(3.0 * moduleSize - stateCount[2]) < 3 * maxVariance &&
Math.abs(moduleSize - stateCount[3]) < maxVariance &&
Math.abs(moduleSize - stateCount[4]) < maxVariance;
}
private getCrossCheckStateCount(): Int32Array {
const crossCheckStateCount = this.crossCheckStateCount;
crossCheckStateCount[0] = 0;
crossCheckStateCount[1] = 0;
crossCheckStateCount[2] = 0;
crossCheckStateCount[3] = 0;
crossCheckStateCount[4] = 0;
return crossCheckStateCount;
}
/**
* After a vertical and horizontal scan finds a potential finder pattern, this method
* "cross-cross-cross-checks" by scanning down diagonally through the center of the possible
* finder pattern to see if the same proportion is detected.
*
* @param startI row where a finder pattern was detected
* @param centerJ center of the section that appears to cross a finder pattern
* @param maxCount maximum reasonable number of modules that should be
* observed in any reading state, based on the results of the horizontal scan
* @param originalStateCountTotal The original state count total.
* @return true if proportions are withing expected limits
*/
private crossCheckDiagonal(startI: number /*int*/, centerJ: number /*int*/, maxCount: number /*int*/, originalStateCountTotal: number /*int*/): boolean {
const stateCount: Int32Array = this.getCrossCheckStateCount();
// Start counting up, left from center finding black center mass
let i = 0;
const image = this.image;
while (startI >= i && centerJ >= i && image.get(centerJ - i, startI - i)) {
stateCount[2]++;
i++;
}
if (startI < i || centerJ < i) {
return false;
}
// Continue up, left finding white space
while (startI >= i && centerJ >= i && !image.get(centerJ - i, startI - i) &&
stateCount[1] <= maxCount) {
stateCount[1]++;
i++;
}
// If already too many modules in this state or ran off the edge:
if (startI < i || centerJ < i || stateCount[1] > maxCount) {
return false;
}
// Continue up, left finding black border
while (startI >= i && centerJ >= i && image.get(centerJ - i, startI - i) &&
stateCount[0] <= maxCount) {
stateCount[0]++;
i++;
}
if (stateCount[0] > maxCount) {
return false;
}
const maxI = image.getHeight();
const maxJ = image.getWidth();
// Now also count down, right from center
i = 1;
while (startI + i < maxI && centerJ + i < maxJ && image.get(centerJ + i, startI + i)) {
stateCount[2]++;
i++;
}
// Ran off the edge?
if (startI + i >= maxI || centerJ + i >= maxJ) {
return false;
}
while (startI + i < maxI && centerJ + i < maxJ && !image.get(centerJ + i, startI + i) &&
stateCount[3] < maxCount) {
stateCount[3]++;
i++;
}
if (startI + i >= maxI || centerJ + i >= maxJ || stateCount[3] >= maxCount) {
return false;
}
while (startI + i < maxI && centerJ + i < maxJ && image.get(centerJ + i, startI + i) &&
stateCount[4] < maxCount) {
stateCount[4]++;
i++;
}
if (stateCount[4] >= maxCount) {
return false;
}
// If we found a finder-pattern-like section, but its size is more than 100% different than
// the original, assume it's a false positive
const stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2] + stateCount[3] + stateCount[4];
return Math.abs(stateCountTotal - originalStateCountTotal) < 2 * originalStateCountTotal &&
FinderPatternFinder.foundPatternCross(stateCount);
}
/**
* <p>After a horizontal scan finds a potential finder pattern, this method
* "cross-checks" by scanning down vertically through the center of the possible
* finder pattern to see if the same proportion is detected.</p>
*
* @param startI row where a finder pattern was detected
* @param centerJ center of the section that appears to cross a finder pattern
* @param maxCount maximum reasonable number of modules that should be
* observed in any reading state, based on the results of the horizontal scan
* @return vertical center of finder pattern, or {@link Float#NaN} if not found
*/
private crossCheckVertical(startI: number /*int*/, centerJ: number /*int*/, maxCount: number /*int*/,
originalStateCountTotal: number /*int*/): number/*float*/ {
const image: BitMatrix = this.image;
const maxI = image.getHeight();
const stateCount: Int32Array = this.getCrossCheckStateCount();
// Start counting up from center
let i = startI;
while (i >= 0 && image.get(centerJ, i)) {
stateCount[2]++;
i--;
}
if (i < 0) {
return NaN;
}
while (i >= 0 && !image.get(centerJ, i) && stateCount[1] <= maxCount) {
stateCount[1]++;
i--;
}
// If already too many modules in this state or ran off the edge:
if (i < 0 || stateCount[1] > maxCount) {
return NaN;
}
while (i >= 0 && image.get(centerJ, i) && stateCount[0] <= maxCount) {
stateCount[0]++;
i--;
}
if (stateCount[0] > maxCount) {
return NaN;
}
// Now also count down from center
i = startI + 1;
while (i < maxI && image.get(centerJ, i)) {
stateCount[2]++;
i++;
}
if (i === maxI) {
return NaN;
}
while (i < maxI && !image.get(centerJ, i) && stateCount[3] < maxCount) {
stateCount[3]++;
i++;
}
if (i === maxI || stateCount[3] >= maxCount) {
return NaN;
}
while (i < maxI && image.get(centerJ, i) && stateCount[4] < maxCount) {
stateCount[4]++;
i++;
}
if (stateCount[4] >= maxCount) {
return NaN;
}
// If we found a finder-pattern-like section, but its size is more than 40% different than
// the original, assume it's a false positive
const stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2] + stateCount[3] +
stateCount[4];
if (5 * Math.abs(stateCountTotal - originalStateCountTotal) >= 2 * originalStateCountTotal) {
return NaN;
}
return FinderPatternFinder.foundPatternCross(stateCount) ? FinderPatternFinder.centerFromEnd(stateCount, i) : NaN;
}
/**
* <p>Like {@link #crossCheckVertical(int, int, int, int)}, and in fact is basically identical,
* except it reads horizontally instead of vertically. This is used to cross-cross
* check a vertical cross check and locate the real center of the alignment pattern.</p>
*/
private crossCheckHorizontal(startJ: number /*int*/, centerI: number /*int*/, maxCount: number /*int*/,
originalStateCountTotal: number /*int*/): number/*float*/ {
const image: BitMatrix = this.image;
const maxJ = image.getWidth();
const stateCount: Int32Array = this.getCrossCheckStateCount();
let j = startJ;
while (j >= 0 && image.get(j, centerI)) {
stateCount[2]++;
j--;
}
if (j < 0) {
return NaN;
}
while (j >= 0 && !image.get(j, centerI) && stateCount[1] <= maxCount) {
stateCount[1]++;
j--;
}
if (j < 0 || stateCount[1] > maxCount) {
return NaN;
}
while (j >= 0 && image.get(j, centerI) && stateCount[0] <= maxCount) {
stateCount[0]++;
j--;
}
if (stateCount[0] > maxCount) {
return NaN;
}
j = startJ + 1;
while (j < maxJ && image.get(j, centerI)) {
stateCount[2]++;
j++;
}
if (j === maxJ) {
return NaN;
}
while (j < maxJ && !image.get(j, centerI) && stateCount[3] < maxCount) {
stateCount[3]++;
j++;
}
if (j === maxJ || stateCount[3] >= maxCount) {
return NaN;
}
while (j < maxJ && image.get(j, centerI) && stateCount[4] < maxCount) {
stateCount[4]++;
j++;
}
if (stateCount[4] >= maxCount) {
return NaN;
}
// If we found a finder-pattern-like section, but its size is significantly different than
// the original, assume it's a false positive
const stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2] + stateCount[3] +
stateCount[4];
if (5 * Math.abs(stateCountTotal - originalStateCountTotal) >= originalStateCountTotal) {
return NaN;
}
return FinderPatternFinder.foundPatternCross(stateCount) ? FinderPatternFinder.centerFromEnd(stateCount, j) : NaN;
}
/**
* <p>This is called when a horizontal scan finds a possible alignment pattern. It will
* cross check with a vertical scan, and if successful, will, ah, cross-cross-check
* with another horizontal scan. This is needed primarily to locate the real horizontal
* center of the pattern in cases of extreme skew.
* And then we cross-cross-cross check with another diagonal scan.</p>
*
* <p>If that succeeds the finder pattern location is added to a list that tracks
* the number of times each location has been nearly-matched as a finder pattern.
* Each additional find is more evidence that the location is in fact a finder
* pattern center
*
* @param stateCount reading state module counts from horizontal scan
* @param i row where finder pattern may be found
* @param j end of possible finder pattern in row
* @param pureBarcode true if in "pure barcode" mode
* @return true if a finder pattern candidate was found this time
*/
protected handlePossibleCenter(stateCount: Int32Array, i: number /*int*/, j: number /*int*/, pureBarcode: boolean): boolean {
const stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2] + stateCount[3] +
stateCount[4];
let centerJ: number /*float*/ = FinderPatternFinder.centerFromEnd(stateCount, j);
let centerI: number /*float*/ = this.crossCheckVertical(i, /*(int) */Math.floor(centerJ), stateCount[2], stateCountTotal);
if (!isNaN(centerI)) {
// Re-cross check
centerJ = this.crossCheckHorizontal(/*(int) */Math.floor(centerJ), /*(int) */Math.floor(centerI), stateCount[2], stateCountTotal);
if (!isNaN(centerJ) &&
(!pureBarcode || this.crossCheckDiagonal(/*(int) */Math.floor(centerI), /*(int) */Math.floor(centerJ), stateCount[2], stateCountTotal))) {
const estimatedModuleSize: number /*float*/ = stateCountTotal / 7.0;
let found: boolean = false;
const possibleCenters = this.possibleCenters;
for (let index = 0, length = possibleCenters.length; index < length; index++) {
const center: FinderPattern = possibleCenters[index];
// Look for about the same center and module size:
if (center.aboutEquals(estimatedModuleSize, centerI, centerJ)) {
possibleCenters[index] = center.combineEstimate(centerI, centerJ, estimatedModuleSize);
found = true;
break;
}
}
if (!found) {
const point: FinderPattern = new FinderPattern(centerJ, centerI, estimatedModuleSize);
possibleCenters.push(point);
if (this.resultPointCallback !== null && this.resultPointCallback !== undefined) {
this.resultPointCallback.foundPossibleResultPoint(point);
}
}
return true;
}
}
return false;
}
/**
* @return number of rows we could safely skip during scanning, based on the first
* two finder patterns that have been located. In some cases their position will
* allow us to infer that the third pattern must lie below a certain point farther
* down in the image.
*/
private findRowSkip(): number /*int*/ {
const max = this.possibleCenters.length;
if (max <= 1) {
return 0;
}
let firstConfirmedCenter: ResultPoint = null;
for (const center of this.possibleCenters) {
if (center.getCount() >= FinderPatternFinder.CENTER_QUORUM) {
if (firstConfirmedCenter == null) {
firstConfirmedCenter = center;
} else {
// We have two confirmed centers
// How far down can we skip before resuming looking for the next
// pattern? In the worst case, only the difference between the
// difference in the x / y coordinates of the two centers.
// This is the case where you find top left last.
this.hasSkipped = true;
return /*(int) */Math.floor((Math.abs(firstConfirmedCenter.getX() - center.getX()) -
Math.abs(firstConfirmedCenter.getY() - center.getY())) / 2);
}
}
}
return 0;
}
/**
* @return true iff we have found at least 3 finder patterns that have been detected
* at least {@link #CENTER_QUORUM} times each, and, the estimated module size of the
* candidates is "pretty similar"
*/
private haveMultiplyConfirmedCenters(): boolean {
let confirmedCount = 0;
let totalModuleSize: number /*float*/ = 0.0;
const max = this.possibleCenters.length;
for (const pattern of this.possibleCenters) {
if (pattern.getCount() >= FinderPatternFinder.CENTER_QUORUM) {
confirmedCount++;
totalModuleSize += pattern.getEstimatedModuleSize();
}
}
if (confirmedCount < 3) {
return false;
}
// OK, we have at least 3 confirmed centers, but, it's possible that one is a "false positive"
// and that we need to keep looking. We detect this by asking if the estimated module sizes
// vary too much. We arbitrarily say that when the total deviation from average exceeds
// 5% of the total module size estimates, it's too much.
const average: number /*float*/ = totalModuleSize / max;
let totalDeviation: number /*float*/ = 0.0;
for (const pattern of this.possibleCenters) {
totalDeviation += Math.abs(pattern.getEstimatedModuleSize() - average);
}
return totalDeviation <= 0.05 * totalModuleSize;
}
/**
* @return the 3 best {@link FinderPattern}s from our list of candidates. The "best" are
* those that have been detected at least {@link #CENTER_QUORUM} times, and whose module
* size differs from the average among those patterns the least
* @throws NotFoundException if 3 such finder patterns do not exist
*/
private selectBestPatterns(): FinderPattern[] /*throws NotFoundException */ {
const startSize = this.possibleCenters.length;
if (startSize < 3) {
// Couldn't find enough finder patterns
throw new NotFoundException();
}
const possibleCenters = this.possibleCenters;
let average: float;
// Filter outlier possibilities whose module size is too different
if (startSize > 3) {
// But we can only afford to do so if we have at least 4 possibilities to choose from
let totalModuleSize: float = 0.0;
let square: float = 0.0;
for (const center of this.possibleCenters) {
const size: float = center.getEstimatedModuleSize();
totalModuleSize += size;
square += size * size;
}
average = totalModuleSize / startSize;
let stdDev: float = <float>Math.sqrt(square / startSize - average * average);
possibleCenters.sort(
/**
* <p>Orders by furthest from average</p>
*/
// FurthestFromAverageComparator implements Comparator<FinderPattern>
(center1: FinderPattern, center2: FinderPattern) => {
const dA: float = Math.abs(center2.getEstimatedModuleSize() - average);
const dB: float = Math.abs(center1.getEstimatedModuleSize() - average);
return dA < dB ? -1 : dA > dB ? 1 : 0;
});
const limit: float = Math.max(0.2 * average, stdDev);
for (let i = 0; i < possibleCenters.length && possibleCenters.length > 3; i++) {
const pattern: FinderPattern = possibleCenters[i];
if (Math.abs(pattern.getEstimatedModuleSize() - average) > limit) {
possibleCenters.splice(i, 1);
i--;
}
}
}
if (possibleCenters.length > 3) {
// Throw away all but those first size candidate points we found.
let totalModuleSize: float = 0.0;
for (const possibleCenter of possibleCenters) {
totalModuleSize += possibleCenter.getEstimatedModuleSize();
}
average = totalModuleSize / possibleCenters.length;
possibleCenters.sort(
/**
* <p>Orders by {@link FinderPattern#getCount()}, descending.</p>
*/
// CenterComparator implements Comparator<FinderPattern>
(center1: FinderPattern, center2: FinderPattern) => {
if (center2.getCount() === center1.getCount()) {
const dA: float = Math.abs(center2.getEstimatedModuleSize() - average);
const dB: float = Math.abs(center1.getEstimatedModuleSize() - average);
return dA < dB ? 1 : dA > dB ? -1 : 0;
} else {
return center2.getCount() - center1.getCount();
}
});
possibleCenters.splice(3); // this is not realy necessary as we only return first 3 anyway
}
return [
possibleCenters[0],
possibleCenters[1],
possibleCenters[2]
];
}
}