dependencies {
...
    compile 'rpalcolea.gravatar:gravatar:1.0.0'
...
}

 /**
     * @attr email    REQUIRED	the startDate for styling
     * @attr size          the disired dimensions in pixels for the gravatar image (from 1 up to 512)
     * @attr alt          alt-attribute for the resulting img-element
     * @attr cssClass        class-attribute for the resulting img-element
     * @attr title          title-attribute for the resulting img-element
     * @attr id            id-attribute for the resulting img-element
     * @attr name          name-attribute for the resulting img-element
     * @attr defaultGravatarUrl    the default image to display if no gravatar is found; may be a URL or one of the following (defaults to the official Gravatar logo):
     * 								<li>404: do not load any image if none is associated with the email hash, instead return an HTTP 404 (File Not Found) response
     * 								<li>mm: (mystery-man) a simple, cartoon-style silhouetted outline of a person (does not vary by email hash)
     * 								<li>identicon: a geometric pattern based on an email hash
     * 								<li>monsterid: a generated 'monster' with different colors, faces, etc
     * 								<li>wavatar: generated faces with differing features and backgrounds
     * 								<li>retro: awesome generated, 8-bit arcade-style pixelated faces
     * @attr gravatarRating      desired image rating censor-level; may be one of the following:
     * 								<li>g (default): suitable for display on all websites with any audience type.
     * 								<li>pg: may contain rude gestures, provocatively dressed individuals, the lesser swear words, or mild violence.
     * 								<li>r: may contain such things as harsh profanity, intense violence, nudity, or hard drug use.
     * 								<li>x: may contain hardcore sexual imagery or extremely disturbing violence.
     */

GravatarUrlGenerator.generateUrl('[email protected]')

  GravatarRating rating
  Integer size
  String defaultImage