android/provider/MetadataReader.java

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * 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 android.provider;

import android.annotation.Nullable;
import android.media.ExifInterface;
import android.os.Bundle;

import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Class providing support for extracting metadata from a file as a
 * {@link Bundle} suitable for use with {@link DocumentsContract#getDocumentMetadata}.
 * <p>Currently only EXIF data is supported.
 * <p>TODO: Add support for common video and audio types, as well as PDF files.
 * {@hide}
 */
public final class MetadataReader {

    private MetadataReader() {}

    private static final String[] DEFAULT_EXIF_TAGS = {
            ExifInterface.TAG_APERTURE,
            ExifInterface.TAG_COPYRIGHT,
            ExifInterface.TAG_DATETIME,
            ExifInterface.TAG_EXPOSURE_TIME,
            ExifInterface.TAG_FOCAL_LENGTH,
            ExifInterface.TAG_F_NUMBER,
            ExifInterface.TAG_GPS_LATITUDE,
            ExifInterface.TAG_GPS_LATITUDE_REF,
            ExifInterface.TAG_GPS_LONGITUDE,
            ExifInterface.TAG_GPS_LONGITUDE_REF,
            ExifInterface.TAG_IMAGE_LENGTH,
            ExifInterface.TAG_IMAGE_WIDTH,
            ExifInterface.TAG_ISO_SPEED_RATINGS,
            ExifInterface.TAG_MAKE,
            ExifInterface.TAG_MODEL,
            ExifInterface.TAG_ORIENTATION,
            ExifInterface.TAG_SHUTTER_SPEED_VALUE,
    };

    private static final int TYPE_INT = 0;
    private static final int TYPE_DOUBLE = 1;
    private static final int TYPE_STRING = 2;

    private static final Map<String, Integer> TYPE_MAPPING = new HashMap<>();
    static {
        // TODO: Move this over to ExifInterface.java
        // Since each ExifInterface item has a type, and there's currently no way to get the type
        // from the tag, here we identify the tag to the type so that we can call the correct
        // ExifInterface method
        TYPE_MAPPING.put(ExifInterface.TAG_ARTIST, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_BITS_PER_SAMPLE, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_COMPRESSION, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_COPYRIGHT, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_DATETIME, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_IMAGE_DESCRIPTION, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_IMAGE_LENGTH, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_IMAGE_WIDTH, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_JPEG_INTERCHANGE_FORMAT, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_JPEG_INTERCHANGE_FORMAT_LENGTH, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_MAKE, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_MODEL, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_ORIENTATION, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_PHOTOMETRIC_INTERPRETATION, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_PLANAR_CONFIGURATION, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_PRIMARY_CHROMATICITIES, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_REFERENCE_BLACK_WHITE, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_RESOLUTION_UNIT, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_ROWS_PER_STRIP, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_SAMPLES_PER_PIXEL, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_SOFTWARE, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_STRIP_BYTE_COUNTS, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_STRIP_OFFSETS, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_TRANSFER_FUNCTION, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_WHITE_POINT, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_X_RESOLUTION, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_Y_CB_CR_COEFFICIENTS, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_Y_CB_CR_POSITIONING, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_Y_CB_CR_SUB_SAMPLING, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_Y_RESOLUTION, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_APERTURE_VALUE, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_BRIGHTNESS_VALUE, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_CFA_PATTERN, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_COLOR_SPACE, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_COMPONENTS_CONFIGURATION, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_COMPRESSED_BITS_PER_PIXEL, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_CONTRAST, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_CUSTOM_RENDERED, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_DATETIME_DIGITIZED, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_DATETIME_ORIGINAL, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_DEVICE_SETTING_DESCRIPTION, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_DIGITAL_ZOOM_RATIO, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_EXIF_VERSION, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_EXPOSURE_BIAS_VALUE, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_EXPOSURE_INDEX, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_EXPOSURE_MODE, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_EXPOSURE_PROGRAM, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_EXPOSURE_TIME, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_F_NUMBER, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_FILE_SOURCE, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_FLASH, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_FLASH_ENERGY, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_FLASHPIX_VERSION, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_FOCAL_LENGTH, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_FOCAL_LENGTH_IN_35MM_FILM, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_FOCAL_PLANE_RESOLUTION_UNIT, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_FOCAL_PLANE_X_RESOLUTION, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_FOCAL_PLANE_Y_RESOLUTION, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_GAIN_CONTROL, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_ISO_SPEED_RATINGS, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_IMAGE_UNIQUE_ID, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_LIGHT_SOURCE, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_MAKER_NOTE, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_MAX_APERTURE_VALUE, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_METERING_MODE, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_NEW_SUBFILE_TYPE, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_OECF, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_PIXEL_X_DIMENSION, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_PIXEL_Y_DIMENSION, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_RELATED_SOUND_FILE, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_SATURATION, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_SCENE_CAPTURE_TYPE, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_SCENE_TYPE, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_SENSING_METHOD, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_SHARPNESS, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_SHUTTER_SPEED_VALUE, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_SPATIAL_FREQUENCY_RESPONSE, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_SPECTRAL_SENSITIVITY, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_SUBFILE_TYPE, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_SUBSEC_TIME, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_SUBSEC_TIME_DIGITIZED, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_SUBSEC_TIME_ORIGINAL, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_SUBJECT_AREA, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_SUBJECT_DISTANCE, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_SUBJECT_DISTANCE_RANGE, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_SUBJECT_LOCATION, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_USER_COMMENT, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_WHITE_BALANCE, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_ALTITUDE, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_ALTITUDE_REF, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_AREA_INFORMATION, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_DOP, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_DATESTAMP, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_DEST_BEARING, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_DEST_BEARING_REF, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_DEST_DISTANCE, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_DEST_DISTANCE_REF, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_DEST_LATITUDE, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_DEST_LATITUDE_REF, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_DEST_LONGITUDE, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_DEST_LONGITUDE_REF, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_DIFFERENTIAL, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_IMG_DIRECTION, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_IMG_DIRECTION_REF, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_LATITUDE, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_LATITUDE_REF, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_LONGITUDE, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_LONGITUDE_REF, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_MAP_DATUM, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_MEASURE_MODE, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_PROCESSING_METHOD, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_SATELLITES, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_SPEED, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_SPEED_REF, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_STATUS, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_TIMESTAMP, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_TRACK, TYPE_DOUBLE);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_TRACK_REF, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_GPS_VERSION_ID, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_INTEROPERABILITY_INDEX, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_THUMBNAIL_IMAGE_LENGTH, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_THUMBNAIL_IMAGE_WIDTH, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_DNG_VERSION, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_DEFAULT_CROP_SIZE, TYPE_INT);
        //I don't know how to represent this. Type is unknown
        //TYPE_MAPPING.put(ExifInterface.TAG_ORF_THUMBNAIL_IMAGE, TYPE_STRING);
        TYPE_MAPPING.put(ExifInterface.TAG_ORF_PREVIEW_IMAGE_START, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_ORF_PREVIEW_IMAGE_LENGTH, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_ORF_ASPECT_FRAME, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_RW2_SENSOR_BOTTOM_BORDER, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_RW2_SENSOR_LEFT_BORDER, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_RW2_SENSOR_RIGHT_BORDER, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_RW2_SENSOR_TOP_BORDER, TYPE_INT);
        TYPE_MAPPING.put(ExifInterface.TAG_RW2_ISO, TYPE_INT);
    }
    private static final String JPG_MIME_TYPE = "image/jpg";
    private static final String JPEG_MIME_TYPE = "image/jpeg";


    /**
     * Returns true if caller can generally expect to get metadata results
     * for the supplied mimetype.
     */
    public static boolean isSupportedMimeType(String mimeType) {
        return JPG_MIME_TYPE.equals(mimeType) || JPEG_MIME_TYPE.equals(mimeType);
    }

    /**
     * Generic metadata retrieval method that can retrieve any available metadata from a given doc
     * Currently only functions for exifdata
     *
     * @param metadata the bundle to which we add any relevant metadata
     * @param stream InputStream containing a file
     * @param mimeType type of the given file
     * @param tags a variable amount of keys to differentiate which tags the user wants
     *             if null, returns a default set of data. See {@link DEFAULT_EXIF_TAGS}.
     * @throws IOException when the file doesn't exist
     */
    public static void getMetadata(Bundle metadata, InputStream stream, String mimeType,
            @Nullable String[] tags) throws IOException {
        List<String> metadataTypes = new ArrayList<>();
        if (isSupportedMimeType(mimeType)) {
            Bundle exifData = getExifData(stream, tags);
            if (exifData.size() > 0) {
                metadata.putBundle(DocumentsContract.METADATA_EXIF, exifData);
                metadataTypes.add(DocumentsContract.METADATA_EXIF);
            }
        }
        metadata.putStringArray(DocumentsContract.METADATA_TYPES,
                metadataTypes.toArray(new String[metadataTypes.size()]));
        // TODO: Add support for PDF and Video metadata
        // TODO: Broaden image support to all images
    }

    /**
     * Helper method that is called if getMetadata is called for an image mimeType.
     *
     * @param stream the input stream from which to extra data.
     * @param tags a list of ExifInterface tags that are used to retrieve data.
     *             if null, returns a default set of data. See {@link DEFAULT_EXIF_TAGS}.
     */
    private static Bundle getExifData(InputStream stream, @Nullable String[] tags)
            throws IOException {
        if (tags == null) {
            tags = DEFAULT_EXIF_TAGS;
        }

        ExifInterface exifInterface = new ExifInterface(stream);
        Bundle exif = new Bundle();
        for (String tag : tags) {
            if (TYPE_MAPPING.get(tag).equals(TYPE_INT)) {
                int data = exifInterface.getAttributeInt(tag, Integer.MIN_VALUE);
                if (data != Integer.MIN_VALUE) {
                    exif.putInt(tag, data);
                }
            } else if (TYPE_MAPPING.get(tag).equals(TYPE_DOUBLE)) {
                double data = exifInterface.getAttributeDouble(tag, Double.MIN_VALUE);
                if (data != Double.MIN_VALUE) {
                    exif.putDouble(tag, data);
                }
            } else if (TYPE_MAPPING.get(tag).equals(TYPE_STRING)) {
                String data = exifInterface.getAttribute(tag);
                if (data != null) {
                    exif.putString(tag, data);
                }
            }
        }
        return exif;
    }
}