直接上源码↓↓↓

  /**
   * Sets the {@link ImageView} the resource will be loaded into, cancels any existing loads into
   * the view, and frees any resources Glide may have previously loaded into the view so they may be
   * reused.
   *
   * @see RequestManager#clear(Target)
   *
   * @param view The view to cancel previous loads for and load the new resource into.
   * @return The
   * {@link com.bumptech.glide.request.target.Target} used to wrap the given {@link ImageView}.
   */
  @NonNull
  public ViewTarget<ImageView, TranscodeType> into(@NonNull ImageView view) {
    Util.assertMainThread();
    Preconditions.checkNotNull(view);

    RequestOptions requestOptions = this.requestOptions;
    if (!requestOptions.isTransformationSet()
        && requestOptions.isTransformationAllowed()
        && view.getScaleType() != null) {
      // Clone in this method so that if we use this RequestBuilder to load into a View and then
      // into a different target, we don't retain the transformation applied based on the previous
      // View's scale type.
      switch (view.getScaleType()) {
        case CENTER_CROP:
          requestOptions = requestOptions.clone().optionalCenterCrop();
          break;
        case CENTER_INSIDE:
          requestOptions = requestOptions.clone().optionalCenterInside();
          break;
        case FIT_CENTER:
        case FIT_START:
        case FIT_END:
          requestOptions = requestOptions.clone().optionalFitCenter();
          break;
        case FIT_XY:
          requestOptions = requestOptions.clone().optionalCenterInside();
          break;
        case CENTER:
        case MATRIX:
        default:
          // Do nothing.
      }
    }

    return into(
        glideContext.buildImageViewTarget(view, transcodeClass),
        /*targetListener=*/ null,
        requestOptions);
  }

可以发现如果requestOption中没有设置过transformation或dontTransform，最后通过