ImageOrientationHelper.java

package com.flt.bothie2.utility;

import android.graphics.Bitmap;
import android.graphics.Matrix;
import android.media.ExifInterface;
import android.util.Log;
import android.util.Pair;

import com.drew.imaging.ImageMetadataReader;
import com.drew.metadata.Directory;
import com.drew.metadata.Metadata;
import com.drew.metadata.MetadataException;
import com.drew.metadata.exif.ExifIFD0Directory;
import com.drew.metadata.exif.ExifImageDirectory;

import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

/**
 * This class provides helper methods to manage the inspection of images that support the EXIF
 * format, and the rotation of a Bitmap to orient it correctly according to this information.
 * The supporting EXIF library is: https://github.com/drewnoakes/metadata-extractor
 */
public class ImageOrientationHelper {
  private static final String TAG = "IOH";

  public static Bitmap rotateImage(Bitmap bmp, float rotation) {
    Matrix matrix = new Matrix();
    matrix.postRotate(rotation);
    return applyMatrix(bmp, matrix);
  }

  public static Bitmap applyMatrix(Bitmap bmp, Matrix matrix) {
    return Bitmap.createBitmap(bmp, 0, 0, bmp.getWidth(), bmp.getHeight(), matrix, true);
  }

  public static Integer getOrientationFromExifDataIn(InputStream stream) throws Exception {
    Metadata metadata = ImageMetadataReader.readMetadata(stream);

    List<Pair<Directory, Integer>> pairs = new ArrayList<>();
    pairs.add(new Pair<Directory, Integer>(metadata.getFirstDirectoryOfType(ExifIFD0Directory.class), ExifIFD0Directory.TAG_ORIENTATION));
    pairs.add(new Pair<Directory, Integer>(metadata.getFirstDirectoryOfType(ExifImageDirectory.class), ExifImageDirectory.TAG_ORIENTATION));

    Integer orientation = null;
    try {
      for (Pair<Directory,Integer> pair : pairs) {
        Directory directory = pair.first; Integer tag = pair.second;
        if (directory != null && directory.containsTag(tag)) {
          orientation = directory.getInt(tag);
        } else {
          Log.w(TAG, "TAG_ORIENTATION was not found in " + directory.getName());
        }
      }
    } catch (MetadataException me) {
      Log.w(TAG, "Could not extract orientation metadata.");
    }
    return orientation;
  }

  public static Matrix matrixForOrientation(int orientation) {
    Matrix matrix = new Matrix();

    switch (orientation) {
      case ExifInterface.ORIENTATION_NORMAL:
        // NOP
        break;
      case ExifInterface.ORIENTATION_FLIP_HORIZONTAL:
        matrix.setScale(-1, 1);
        break;
      case ExifInterface.ORIENTATION_ROTATE_180:
        matrix.setRotate(180);
        break;
      case ExifInterface.ORIENTATION_FLIP_VERTICAL:
        matrix.setRotate(180);
        matrix.postScale(-1, 1);
        break;
      case ExifInterface.ORIENTATION_TRANSPOSE:
        matrix.setRotate(90);
        matrix.postScale(-1, 1);
        break;
      case ExifInterface.ORIENTATION_ROTATE_90:
        matrix.setRotate(90);
        break;
      case ExifInterface.ORIENTATION_TRANSVERSE:
        matrix.setRotate(-90);
        matrix.postScale(-1, 1);
        break;
      case ExifInterface.ORIENTATION_ROTATE_270:
        matrix.setRotate(-90);
        break;
      default:
        Log.w(TAG, "Unexpected exif orientation value:" + orientation);
        break;
    }

    return matrix;
  }
}