wro4j-core/src/main/java/ro/isdc/wro/model/resource/processor/impl/css/AbstractCssUrlRewritingProcessor.java
protected boolean isReplaceNeeded(final String url) {
    return !(UrlUriLocator.isValid(url) || DataUriGenerator.isDataUri(url.trim()));
  }
protected boolean isReplaceNeeded(final String url) {
    return !(UrlUriLocator.isValid(url) || DataUriGenerator.isDataUri(url.trim()));
  }
Check if url must be replaced or not. The replacement is not needed if the url of the image is absolute (can be
resolved by urlResourceLocator) or if the url is a data uri (base64 encoded value).

@param url
to check.
@return true if url needs to be replaced or remain unchanged.