code: private void setParameterValue(CmsObject cms, String key, String value) {
  
          if (m_parameters == null) {
              m_parameters = getParameterMap(getStringValue(cms));
          }
          if (CmsStringUtil.isEmptyOrWhitespaceOnly(value) && m_parameters.containsKey(key)) {
              m_parameters.remove(key);
          } else if (CmsStringUtil.isNotEmptyOrWhitespaceOnly(value)) {
              m_parameters.put(key, new String[] {value});
          }
          String result = CmsRequestUtil.getRequestLink(getStringValue(cms));
          result = CmsRequestUtil.appendParameters(result, m_parameters, false);
          setStringValue(cms, result);
      }
docs: Sets a parameter for the image with the provided key as name and the value.<p>
  
  @param cms the current users context
  @param key the parameter name to set
  @param value the value of the parameter