Android图片压缩——Luban鲁班压缩

implementation 'top.zibin:Luban:1.1.3'

Luban.with(this)
        .load(photos)                                   // 传人要压缩的图片列表
        .ignoreBy(100)                                  // 忽略不压缩图片的大小
        .setTargetDir(getPath())                        // 设置压缩后文件存储位置
        .setCompressListener(new OnCompressListener() { //设置回调
          @Override
          public void onStart() {
            // TODO 压缩开始前调用，可以在方法内启动 loading UI
          }

          @Override
          public void onSuccess(File file) {
            // TODO 压缩成功后调用，返回压缩后的图片文件
          }

          @Override
          public void onError(Throwable e) {
            // TODO 当压缩过程出现问题时调用
          }
        }).launch();    //启动压缩

Flowable.just(photos)
    .observeOn(Schedulers.io())
    .map(new Function<List<String>, List<File>>() {
      @Override public List<File> apply(@NonNull List<String> list) throws Exception {
        // 同步方法直接返回压缩后的文件
        return Luban.with(MainActivity.this).load(list).get();
      }
    })
    .observeOn(AndroidSchedulers.mainThread())
    .subscribe();

public static Builder with(Context context) {
    return new Builder(context);
  }

public static class Builder {
    private Context context;//上下文对象
    private String mTargetDir;//压缩后图片存放位置
    private List<String> mPaths;//多个文件的list
    private int mLeastCompressSize = 100;//忽略100kb以下的图片，不压缩
    private OnCompressListener mCompressListener;//回调方法

    Builder(Context context) {
      this.context = context;
      this.mPaths = new ArrayList<>();
    }
    
    private Luban build() {
      return new Luban(this);
    }
}

private Luban(Builder builder) {
    this.mPaths = builder.mPaths;
    this.mTargetDir = builder.mTargetDir;
    this.mCompressListener = builder.mCompressListener;
    this.mLeastCompressSize = builder.mLeastCompressSize;
    mHandler = new Handler(Looper.getMainLooper(), this);
  }

public Builder load(File file) {
      this.mPaths.add(file.getAbsolutePath());
      return this;
    }

    public Builder load(String string) {
      this.mPaths.add(string);
      return this;
    }

    public Builder load(List<String> list) {
      this.mPaths.addAll(list);
      return this;
    }

/**
 * do not compress when the origin image file size less than one value
 *
 * @param size
 *     the value of file size, unit KB, default 100K
 */
public Builder ignoreBy(int size) {
  this.mLeastCompressSize = size;
  return this;
}

public Builder setTargetDir(String targetDir) {
  this.mTargetDir = targetDir;
  return this;
}

public Builder setCompressListener(OnCompressListener listener) {
      this.mCompressListener = listener;
      return this;
    }

/**
 * begin compress image with asynchronous
 */
public void launch() {
  build().launch(context);
}

/**
   * start asynchronous compress thread
   */
  @UiThread private void launch(final Context context) {
    if (mPaths == null || mPaths.size() == 0 && mCompressListener != null) {
      mCompressListener.onError(new NullPointerException("image file cannot be null"));
    }

    Iterator<String> iterator = mPaths.iterator();
    while (iterator.hasNext()) {
      final String path = iterator.next();
      if (Checker.isImage(path)) {
        AsyncTask.SERIAL_EXECUTOR.execute(new Runnable() {
          @Override public void run() {
            try {
              mHandler.sendMessage(mHandler.obtainMessage(MSG_COMPRESS_START));

              File result = Checker.isNeedCompress(mLeastCompressSize, path) ?
                  new Engine(path, getImageCacheFile(context, Checker.checkSuffix(path))).compress() :
                  new File(path);

              mHandler.sendMessage(mHandler.obtainMessage(MSG_COMPRESS_SUCCESS, result));
            } catch (IOException e) {
              mHandler.sendMessage(mHandler.obtainMessage(MSG_COMPRESS_ERROR, e));
            }
          }
        });
      } else {
        Log.e(TAG, "can not read the path : " + path);
      }
      iterator.remove();
    }
  }

File result = Checker.isNeedCompress(mLeastCompressSize, path) ?
                  new Engine(path, getImageCacheFile(context, Checker.checkSuffix(path))).compress() :
                  new File(path);

static boolean isNeedCompress(int leastCompressSize, String path) {
    if (leastCompressSize > 0) {
      File source = new File(path);
      if (!source.exists()) {
        return false;
      }

      if (source.length() <= (leastCompressSize << 10)) {
        return false;
      }
    }
    return true;
  }

Engine(String srcImg, File tagImg) throws IOException {
    if (Checker.isJPG(srcImg)) {
      this.srcExif = new ExifInterface(srcImg);
    }
    this.tagImg = tagImg;
    this.srcImg = srcImg;

    BitmapFactory.Options options = new BitmapFactory.Options();
    options.inJustDecodeBounds = true;
    options.inSampleSize = 1;

    BitmapFactory.decodeFile(srcImg, options);
    this.srcWidth = options.outWidth;
    this.srcHeight = options.outHeight;
  }

/**
   * Returns a mFile with a cache audio name in the private cache directory.
   *
   * @param context
   *     A context.
   */
  private File getImageCacheFile(Context context, String suffix) {
    if (TextUtils.isEmpty(mTargetDir)) {
      mTargetDir = getImageCacheDir(context).getAbsolutePath();
    }

    String cacheBuilder = mTargetDir + "/" +
        System.currentTimeMillis() +
        (int) (Math.random() * 1000) +
        (TextUtils.isEmpty(suffix) ? ".jpg" : suffix);

    return new File(cacheBuilder);
  }

File compress() throws IOException {
    BitmapFactory.Options options = new BitmapFactory.Options();
    options.inSampleSize = computeSize();

    Bitmap tagBitmap = BitmapFactory.decodeFile(srcImg, options);
    ByteArrayOutputStream stream = new ByteArrayOutputStream();

    tagBitmap = rotatingImage(tagBitmap);
    tagBitmap.compress(Bitmap.CompressFormat.JPEG, 60, stream);
    tagBitmap.recycle();

    FileOutputStream fos = new FileOutputStream(tagImg);
    fos.write(stream.toByteArray());
    fos.flush();
    fos.close();
    stream.close();

    return tagImg;
  }

private int computeSize() {
    srcWidth = srcWidth % 2 == 1 ? srcWidth + 1 : srcWidth;
    srcHeight = srcHeight % 2 == 1 ? srcHeight + 1 : srcHeight;

    int longSide = Math.max(srcWidth, srcHeight);
    int shortSide = Math.min(srcWidth, srcHeight);

    float scale = ((float) shortSide / longSide);
    if (scale <= 1 && scale > 0.5625) {
      if (longSide < 1664) {
        return 1;
      } else if (longSide >= 1664 && longSide < 4990) {
        return 2;
      } else if (longSide > 4990 && longSide < 10240) {
        return 4;
      } else {
        return longSide / 1280 == 0 ? 1 : longSide / 1280;
      }
    } else if (scale <= 0.5625 && scale > 0.5) {
      return longSide / 1280 == 0 ? 1 : longSide / 1280;
    } else {
      return (int) Math.ceil(longSide / (1280.0 / scale));
    }
  }

private Bitmap rotatingImage(Bitmap bitmap) {
    if (srcExif == null) return bitmap;

    Matrix matrix = new Matrix();
    int angle = 0;
    int orientation = srcExif.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL);
    switch (orientation) {
      case ExifInterface.ORIENTATION_ROTATE_90:
        angle = 90;
        break;
      case ExifInterface.ORIENTATION_ROTATE_180:
        angle = 180;
        break;
      case ExifInterface.ORIENTATION_ROTATE_270:
        angle = 270;
        break;
    }

    matrix.postRotate(angle);

    return Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);
  }