com.google.zxing.qrcode.QRCodeReader Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of core Show documentation
Show all versions of core Show documentation
Core barcode encoding/decoding library
/*
* 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.
*/
package com.google.zxing.qrcode;
import com.google.zxing.BarcodeFormat;
import com.google.zxing.BinaryBitmap;
import com.google.zxing.ChecksumException;
import com.google.zxing.DecodeHintType;
import com.google.zxing.FormatException;
import com.google.zxing.NotFoundException;
import com.google.zxing.Reader;
import com.google.zxing.Result;
import com.google.zxing.ResultMetadataType;
import com.google.zxing.ResultPoint;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.common.DecoderResult;
import com.google.zxing.common.DetectorResult;
import com.google.zxing.qrcode.decoder.Decoder;
import com.google.zxing.qrcode.decoder.QRCodeDecoderMetaData;
import com.google.zxing.qrcode.detector.Detector;
import java.util.List;
import java.util.Map;
/**
* This implementation can detect and decode QR Codes in an image.
*
* @author Sean Owen
*/
public class QRCodeReader implements Reader {
private static final ResultPoint[] NO_POINTS = new ResultPoint[0];
private final Decoder decoder = new Decoder();
protected final Decoder getDecoder() {
return decoder;
}
/**
* Locates and decodes a QR code in an image.
*
* @return a String representing the content encoded by the QR code
* @throws NotFoundException if a QR code cannot be found
* @throws FormatException if a QR code cannot be decoded
* @throws ChecksumException if error correction fails
*/
@Override
public Result decode(BinaryBitmap image) throws NotFoundException, ChecksumException, FormatException {
return decode(image, null);
}
@Override
public final Result decode(BinaryBitmap image, Map hints)
throws NotFoundException, ChecksumException, FormatException {
DecoderResult decoderResult;
ResultPoint[] points;
if (hints != null && hints.containsKey(DecodeHintType.PURE_BARCODE)) {
BitMatrix bits = extractPureBits(image.getBlackMatrix());
decoderResult = decoder.decode(bits, hints);
points = NO_POINTS;
} else {
DetectorResult detectorResult = new Detector(image.getBlackMatrix()).detect(hints);
decoderResult = decoder.decode(detectorResult.getBits(), hints);
points = detectorResult.getPoints();
}
// If the code was mirrored: swap the bottom-left and the top-right points.
if (decoderResult.getOther() instanceof QRCodeDecoderMetaData) {
((QRCodeDecoderMetaData) decoderResult.getOther()).applyMirroredCorrection(points);
}
Result result = new Result(decoderResult.getText(), decoderResult.getRawBytes(), points, BarcodeFormat.QR_CODE);
List byteSegments = decoderResult.getByteSegments();
if (byteSegments != null) {
result.putMetadata(ResultMetadataType.BYTE_SEGMENTS, byteSegments);
}
String ecLevel = decoderResult.getECLevel();
if (ecLevel != null) {
result.putMetadata(ResultMetadataType.ERROR_CORRECTION_LEVEL, ecLevel);
}
if (decoderResult.hasStructuredAppend()) {
result.putMetadata(ResultMetadataType.STRUCTURED_APPEND_SEQUENCE,
decoderResult.getStructuredAppendSequenceNumber());
result.putMetadata(ResultMetadataType.STRUCTURED_APPEND_PARITY,
decoderResult.getStructuredAppendParity());
}
return result;
}
@Override
public void reset() {
// do nothing
}
/**
* This method detects a code in a "pure" image -- that is, pure monochrome image
* which contains only an unrotated, unskewed, image of a code, with some white border
* around it. This is a specialized method that works exceptionally fast in this special
* case.
*/
private static BitMatrix extractPureBits(BitMatrix image) throws NotFoundException {
int[] leftTopBlack = image.getTopLeftOnBit();
int[] rightBottomBlack = image.getBottomRightOnBit();
if (leftTopBlack == null || rightBottomBlack == null) {
throw NotFoundException.getNotFoundInstance();
}
float moduleSize = moduleSize(leftTopBlack, image);
int top = leftTopBlack[1];
int bottom = rightBottomBlack[1];
int left = leftTopBlack[0];
int right = rightBottomBlack[0];
// Sanity check!
if (left >= right || top >= bottom) {
throw NotFoundException.getNotFoundInstance();
}
if (bottom - top != right - left) {
// Special case, where bottom-right module wasn't black so we found something else in the last row
// Assume it's a square, so use height as the width
right = left + (bottom - top);
if (right >= image.getWidth()) {
// Abort if that would not make sense -- off image
throw NotFoundException.getNotFoundInstance();
}
}
int matrixWidth = Math.round((right - left + 1) / moduleSize);
int matrixHeight = Math.round((bottom - top + 1) / moduleSize);
if (matrixWidth <= 0 || matrixHeight <= 0) {
throw NotFoundException.getNotFoundInstance();
}
if (matrixHeight != matrixWidth) {
// Only possibly decode square regions
throw NotFoundException.getNotFoundInstance();
}
// Push in the "border" by half the module width so that we start
// sampling in the middle of the module. Just in case the image is a
// little off, this will help recover.
int nudge = (int) (moduleSize / 2.0f);
top += nudge;
left += nudge;
// But careful that this does not sample off the edge
// "right" is the farthest-right valid pixel location -- right+1 is not necessarily
// This is positive by how much the inner x loop below would be too large
int nudgedTooFarRight = left + (int) ((matrixWidth - 1) * moduleSize) - right;
if (nudgedTooFarRight > 0) {
if (nudgedTooFarRight > nudge) {
// Neither way fits; abort
throw NotFoundException.getNotFoundInstance();
}
left -= nudgedTooFarRight;
}
// See logic above
int nudgedTooFarDown = top + (int) ((matrixHeight - 1) * moduleSize) - bottom;
if (nudgedTooFarDown > 0) {
if (nudgedTooFarDown > nudge) {
// Neither way fits; abort
throw NotFoundException.getNotFoundInstance();
}
top -= nudgedTooFarDown;
}
// Now just read off the bits
BitMatrix bits = new BitMatrix(matrixWidth, matrixHeight);
for (int y = 0; y < matrixHeight; y++) {
int iOffset = top + (int) (y * moduleSize);
for (int x = 0; x < matrixWidth; x++) {
if (image.get(left + (int) (x * moduleSize), iOffset)) {
bits.set(x, y);
}
}
}
return bits;
}
private static float moduleSize(int[] leftTopBlack, BitMatrix image) throws NotFoundException {
int height = image.getHeight();
int width = image.getWidth();
int x = leftTopBlack[0];
int y = leftTopBlack[1];
boolean inBlack = true;
int transitions = 0;
while (x < width && y < height) {
if (inBlack != image.get(x, y)) {
if (++transitions == 5) {
break;
}
inBlack = !inBlack;
}
x++;
y++;
}
if (x == width || y == height) {
throw NotFoundException.getNotFoundInstance();
}
return (x - leftTopBlack[0]) / 7.0f;
}
}