Jpegのタグを読み込む

JpegTagReader.java

package io.github.usbharu.test.image.xmp;

import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;

public class XmpReader {

  private static boolean exif = false;
  private static boolean xmp = false;

  private static final byte[] exifByteArray = "Exif".getBytes();

  private static final byte[] xmpByteArray = "http://ns.adobe.com/xap/1.0/".getBytes();

  public static void main(String[] args) {
    File file = new File("path/to/image folder");
    for (int i = 0; i < 1; i++) { //ベンチマーク用

      long l = System.currentTimeMillis();
      for (File listFile : file.listFiles((dir, name) -> name.endsWith(".jpg"))) {
        try {
          read(listFile);
        } catch (RuntimeException e) {
          new RuntimeException(listFile.toString(), e).printStackTrace();

        }
      }
      long l1 = System.currentTimeMillis();
      System.out.println(l1 - l);
    }
  }

  public static void read(File file) {
    exif = false;
    xmp = false;
    try (FileInputStream fileInputStream = (new FileInputStream(file))) {
      try (ByteArrayInputStream is = new ByteArrayInputStream(fileInputStream.readAllBytes())) {
        int read = 0;
        while ((!exif && !xmp) && (read = is.read()) != -1) {
          if (read == 0xff) {
            int read1 = is.read();
            short size = (short) (is.read() << 8 | is.read());
            if (read1 == 0xe1) {
              byte[] b = new byte[size - 2];
              is.read(b);
              switchApp(b);
            } else {
              is.skip(size);
            }
          }
        }
      } catch (IOException e) {
        throw new RuntimeException(e);
      }
    } catch (IOException e) {
      throw new RuntimeException(e);
    }
  }

  private static void switchApp(byte[] appSegment) {
    if (Arrays.equals(exifByteArray, 0, 4, appSegment, 0, 4)) {
      exif(appSegment);
      exif = true;
    } else if (Arrays.equals(xmpByteArray, 0, 28, appSegment, 0, 28)) {
      xmp(appSegment);
      xmp = true;

    }
  }

  private static void xmp(byte[] appSegment) {
    System.out.println(new String(appSegment));
  }

  private static void exif(byte[] appSegment) {
    ByteBuffer wrap = ByteBuffer.wrap(appSegment);
    wrap.get(6);
    if (appSegment[6] != (byte) 0x4d && appSegment[7] != (byte) 0x4d) {

      wrap = wrap.order(ByteOrder.LITTLE_ENDIAN);
    }
    wrap.position(10);
    int ifdOffset = wrap.getInt();
    wrap.position(ifdOffset + 6);
    short ifdCount = wrap.getShort();
    for (int i = 0; i < ifdCount; i++) {
      readIfdField(wrap);
    }
  }

  private static void readIfdField(ByteBuffer wrap) {
    byte[] tag = new byte[2];
    wrap.get(tag);
    short type = wrap.getShort();
    int count = wrap.getInt();
    int valueOffset = wrap.getInt();
    int nowPosition = wrap.position();
    if (valueOffset > wrap.limit()) {
      return;
    }
    wrap.position(valueOffset + 6);
    if (type == 1) {
      int valueLength = type * count;
      byte[] value = new byte[valueLength];
      wrap.get(value);
      if (tag[0] == (byte) 0x9c && tag[1] == (byte) 0x9e) {
        String s = new String(value, 0, valueLength - 2, StandardCharsets.UTF_16LE);
        System.out.println(s);
      }

    }
    wrap.position(nowPosition);
  }


  private static String hexToString(byte[] bytes) {
    StringBuilder sb = new StringBuilder();
    for (byte aByte : bytes) {
      sb.append(String.format("%02x", aByte));
    }
    return sb.toString();
  }
}