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Core barcode encoding/decoding library
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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.oned;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.FormatException;
import com.google.zxing.common.BitMatrix;

import java.util.Collection;
import java.util.Collections;

/**
 * This object renders an EAN8 code as a {@link BitMatrix}.
 *
 * @author [email protected] (Ari Pollak)
 */
public final class EAN8Writer extends UPCEANWriter {

  private static final int CODE_WIDTH = 3 + // start guard
      (7 * 4) + // left bars
      5 + // middle guard
      (7 * 4) + // right bars
      3; // end guard

  @Override
  protected Collection getSupportedWriteFormats() {
    return Collections.singleton(BarcodeFormat.EAN_8);
  }

  /**
   * @return a byte array of horizontal pixels (false = white, true = black)
   */
  @Override
  public boolean[] encode(String contents) {
    int length = contents.length();
    switch (length) {
      case 7:
        // No check digit present, calculate it and add it
        int check;
        try {
          check = UPCEANReader.getStandardUPCEANChecksum(contents);
        } catch (FormatException fe) {
          throw new IllegalArgumentException(fe);
        }
        contents += check;
        break;
      case 8:
        try {
          if (!UPCEANReader.checkStandardUPCEANChecksum(contents)) {
            throw new IllegalArgumentException("Contents do not pass checksum");
          }
        } catch (FormatException ignored) {
          throw new IllegalArgumentException("Illegal contents");
        }
        break;
      default:
        throw new IllegalArgumentException(
            "Requested contents should be 7 or 8 digits long, but got " + length);
    }

    checkNumeric(contents);

    boolean[] result = new boolean[CODE_WIDTH];
    int pos = 0;

    pos += appendPattern(result, pos, UPCEANReader.START_END_PATTERN, true);

    for (int i = 0; i <= 3; i++) {
      int digit = Character.digit(contents.charAt(i), 10);
      pos += appendPattern(result, pos, UPCEANReader.L_PATTERNS[digit], false);
    }

    pos += appendPattern(result, pos, UPCEANReader.MIDDLE_PATTERN, false);

    for (int i = 4; i <= 7; i++) {
      int digit = Character.digit(contents.charAt(i), 10);
      pos += appendPattern(result, pos, UPCEANReader.L_PATTERNS[digit], true);
    }
    appendPattern(result, pos, UPCEANReader.START_END_PATTERN, true);

    return result;
  }

}