@Override
  protected void onDraw(Canvas canvas) {

    super.onDraw(canvas);

    // Draw translucent background for the cropped area.
    drawBackground(canvas);

    if (mCropWindowHandler.showGuidelines()) {
      // Determines whether guidelines should be drawn or not
      if (mGuidelines == CropImageView.Guidelines.ON) {
        drawGuidelines(canvas);
      } else if (mGuidelines == CropImageView.Guidelines.ON_TOUCH && mMoveHandler != null) {
        // Draw only when resizing
        drawGuidelines(canvas);
      }
    }

    drawBorders(canvas);

    drawCorners(canvas);
  }
Draw crop overview by drawing background over image not in the cripping area, then borders and
guidelines.
core/src/main/java/com/theartofdev/edmodo/cropper/CropOverlayView.java