+++ /dev/null
-package tim.prune.jpeg.drew;
-
-import java.io.BufferedInputStream;
-import java.io.File;
-import java.io.FileInputStream;
-import java.io.IOException;
-
-import tim.prune.jpeg.JpegData;
-
-
-/**
- * Extracts Exif data from a JPEG header segment
- * Based on Drew Noakes' Metadata extractor at https://drewnoakes.com
- * which in turn is based on code from Jhead http://www.sentex.net/~mwandel/jhead/
- */
-public class ExifReader
-{
- /** Magic numbers to mark the beginning of all Jpegs */
- private static final int MAGIC_JPEG_BYTE_1 = 0xFF;
- private static final int MAGIC_JPEG_BYTE_2 = 0xD8;
-
- /** 6-byte preamble before starting the TIFF data. */
- private static final String JPEG_EXIF_SEGMENT_PREAMBLE = "Exif\0\0";
-
- /** Start of segment marker */
- private static final byte SEGMENT_SOS = (byte) 0xDA;
-
- /** End of segment marker */
- private static final byte MARKER_EOI = (byte) 0xD9;
-
- /**
- * Processes the provided JPEG data, and extracts the specified JPEG segments into a JpegData object.
- * @param inFile a {@link File} from which the JPEG data will be read.
- */
- public static JpegData readMetadata(File inFile) throws ExifException
- {
- JpegData jpegData = new JpegData();
- BufferedInputStream bStream = null;
-
- try
- {
- bStream = new BufferedInputStream(new FileInputStream(inFile));
- byte[] segmentBytes = readSegments(bStream);
- if (segmentBytes != null)
- {
- // Got the bytes for the required segment, now extract the data
- extract(segmentBytes, jpegData);
- }
- }
- catch (IOException ioe) {
- throw new ExifException("IO Exception: " + ioe.getMessage());
- }
- finally
- {
- if (bStream != null) {
- try {
- bStream.close();
- } catch (IOException ioe) {}
- }
- }
- return jpegData;
- }
-
- /**
- * Reads the relevant segment and returns the bytes.
- */
- private static byte[] readSegments(final BufferedInputStream bStream)
- throws ExifException, IOException
- {
- // first two bytes should be JPEG magic number
- final int magic1 = bStream.read() & 0xFF;
- final int magic2 = bStream.read() & 0xFF;
- if (magic1 != MAGIC_JPEG_BYTE_1 || magic2 != MAGIC_JPEG_BYTE_2) {
- throw new ExifException("Jpeg file failed Magic check");
- }
-
- final Byte segmentTypeByte = (byte)0xE1; // JpegSegmentType.APP1.byteValue;
-
- do {
- // Find the segment marker. Markers are zero or more 0xFF bytes, followed
- // by a 0xFF and then a byte not equal to 0x00 or 0xFF.
-
- final short segmentIdentifier = (short) bStream.read();
-
- // We must have at least one 0xFF byte
- if (segmentIdentifier != 0xFF)
- throw new ExifException("Expected JPEG segment start identifier 0xFF, not 0x" + Integer.toHexString(segmentIdentifier).toUpperCase());
-
- // Read until we have a non-0xFF byte. This identifies the segment type.
- byte currSegmentType = (byte) bStream.read();
- while (currSegmentType == (byte)0xFF) {
- currSegmentType = (byte) bStream.read();
- }
-
- if (currSegmentType == 0)
- throw new ExifException("Expected non-zero byte as part of JPEG marker identifier");
-
- if (currSegmentType == SEGMENT_SOS) {
- // The 'Start-Of-Scan' segment's length doesn't include the image data, instead would
- // have to search for the two bytes: 0xFF 0xD9 (EOI).
- // It comes last so simply return at this point
- return null;
- }
-
- if (currSegmentType == MARKER_EOI) {
- // the 'End-Of-Image' segment -- this should never be found in this fashion
- return null;
- }
-
- // next 2-bytes are <segment-size>: [high-byte] [low-byte]
- int segmentLength = (bStream.read() << 8) + bStream.read();
- // segment length includes size bytes, so subtract two
- segmentLength -= 2;
-
- if (segmentLength < 0)
- throw new ExifException("JPEG segment size would be less than zero");
-
- byte[] segmentBytes = new byte[segmentLength];
- int bytesRead = bStream.read(segmentBytes, 0, segmentLength);
- // Bail if not all bytes read in one go - otherwise following sections will be out of step
- if (bytesRead != segmentLength) {
- throw new ExifException("Tried to read " + segmentLength + " bytes but only got " + bytesRead);
- }
- // Check whether we are interested in this segment
- if (segmentTypeByte == currSegmentType)
- {
- // Pass the appropriate byte arrays to reader.
- if (canProcess(segmentBytes)) {
- return segmentBytes;
- }
- }
-
- } while (true);
- }
-
- private static boolean canProcess(final byte[] segmentBytes)
- {
- return segmentBytes.length >= JPEG_EXIF_SEGMENT_PREAMBLE.length() && new String(segmentBytes, 0, JPEG_EXIF_SEGMENT_PREAMBLE.length()).equalsIgnoreCase(JPEG_EXIF_SEGMENT_PREAMBLE);
- }
-
- /**
- * Given the bytes, parse them recursively to fill the JpegData
- * @param segmentBytes bytes out of the file
- * @param jdata jpeg data to be populated
- */
- private static void extract(final byte[] segmentBytes, final JpegData jdata)
- {
- if (segmentBytes == null)
- throw new NullPointerException("segmentBytes cannot be null");
-
- try
- {
- ByteArrayReader reader = new ByteArrayReader(segmentBytes);
-
- // Check for the header preamble
- try {
- if (!reader.getString(0, JPEG_EXIF_SEGMENT_PREAMBLE.length()).equals(JPEG_EXIF_SEGMENT_PREAMBLE)) {
- // TODO what to do with this error state?
- System.err.println("Invalid JPEG Exif segment preamble");
- return;
- }
- } catch (ExifException e) {
- // TODO what to do with this error state?
- e.printStackTrace(System.err);
- return;
- }
-
- // Read the TIFF-formatted Exif data
- TiffProcessor.processTiff(
- reader,
- jdata,
- JPEG_EXIF_SEGMENT_PREAMBLE.length()
- );
-
- } catch (ExifException e) {
- // TODO what to do with this error state?
- e.printStackTrace(System.err);
- } catch (IOException e) {
- // TODO what to do with this error state?
- e.printStackTrace(System.err);
- }
- }
-}
projects / GpsPrune.git / blobdiff