code: public PageSnapshot monochrome(WebElement element) {
          try {
              image = ImageProcessor.monochromeArea(image, new Coordinates(element,devicePixelRatio));
          } catch (RasterFormatException rfe) {
              throw new ElementOutsideViewportException(ELEMENT_OUT_OF_VIEWPORT_EX_MESSAGE, rfe);
          }
          return this;
      }
docs: Makes an element withing a page 'monochrome' - applies gray-and-white filter.
  Original colors remain on the rest of the page.
  
  @param element WebElement within the page to be made 'monochrome'
  @return instance of type PageSnapshot