android set image as contact icon/wallpaper

From the Google Gallery app source code:

// Called when "Set as" is clicked.
private static boolean onSetAsClicked(MenuInvoker onInvoke,
                                      final Activity activity) {
    onInvoke.run(new MenuCallback() {
        public void run(Uri u, IImage image) {
            if (u == null || image == null) {
                return;
            }

            Intent intent = Util.createSetAsIntent(image);
            activity.startActivity(Intent.createChooser(intent,
                    activity.getText(R.string.setImage)));
        }
    });
    return true;
}

From Utils.java

// Returns an intent which is used for "set as" menu items.
public static Intent createSetAsIntent(IImage image) {
    Uri u = image.fullSizeImageUri();
    Intent intent = new Intent(Intent.ACTION_ATTACH_DATA);
    intent.setDataAndType(u, image.getMimeType());
    intent.putExtra("mimeType", image.getMimeType());
    return intent;
}