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/*
* Copyright 2009 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.multi;
import com.google.zxing.BinaryBitmap;
import com.google.zxing.ChecksumException;
import com.google.zxing.FormatException;
import com.google.zxing.NotFoundException;
import com.google.zxing.Reader;
import com.google.zxing.Result;
import java.util.Hashtable;
/**
* This class attempts to decode a barcode from an image, not by scanning the whole image,
* but by scanning subsets of the image. This is important when there may be multiple barcodes in
* an image, and detecting a barcode may find parts of multiple barcode and fail to decode
* (e.g. QR Codes). Instead this scans the four quadrants of the image -- and also the center
* 'quadrant' to cover the case where a barcode is found in the center.
*
* @see GenericMultipleBarcodeReader
*/
public final class ByQuadrantReader implements Reader {
private final Reader delegate;
public ByQuadrantReader(Reader delegate) {
this.delegate = delegate;
}
public Result decode(BinaryBitmap image)
throws NotFoundException, ChecksumException, FormatException {
return decode(image, null);
}
public Result decode(BinaryBitmap image, Hashtable hints)
throws NotFoundException, ChecksumException, FormatException {
int width = image.getWidth();
int height = image.getHeight();
int halfWidth = width / 2;
int halfHeight = height / 2;
BinaryBitmap topLeft = image.crop(0, 0, halfWidth, halfHeight);
try {
return delegate.decode(topLeft, hints);
} catch (NotFoundException re) {
// continue
}
BinaryBitmap topRight = image.crop(halfWidth, 0, halfWidth, halfHeight);
try {
return delegate.decode(topRight, hints);
} catch (NotFoundException re) {
// continue
}
BinaryBitmap bottomLeft = image.crop(0, halfHeight, halfWidth, halfHeight);
try {
return delegate.decode(bottomLeft, hints);
} catch (NotFoundException re) {
// continue
}
BinaryBitmap bottomRight = image.crop(halfWidth, halfHeight, halfWidth, halfHeight);
try {
return delegate.decode(bottomRight, hints);
} catch (NotFoundException re) {
// continue
}
int quarterWidth = halfWidth / 2;
int quarterHeight = halfHeight / 2;
BinaryBitmap center = image.crop(quarterWidth, quarterHeight, halfWidth, halfHeight);
return delegate.decode(center, hints);
}
public void reset() {
delegate.reset();
}
}
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