def gamma_adjust(img, gamma=1.0):
    """
    CommandLine:
        python -m vtool_ibeis.blend --test-gamma_adjust:0 --show

    Ignore:
        >>> # DISABLE_DOCTEST
        >>> from vtool_ibeis.blend import *  # NOQA
        >>> import vtool_ibeis as vt
        >>> test_func = gamma_adjust
        >>> img_fpath = ut.grab_test_imgpath('carl.jpg')
        >>> img = vt.rectify_to_float01(vt.imread(img_fpath))
        >>> args = (img,)
        >>> param_info = ut.ParamInfoList('blend_params', [
        ...    ut.ParamInfo('gamma', .8, 'gamma=',
        ...                 varyvals=np.linspace(.1, 2.5, 25).tolist()),
        ... ])
        >>> gridsearch_image_function(param_info, test_func, args)
        >>> ut.show_if_requested()
    """
    assert img.max() <= 1.0
    assert img.min() >= 0.0
    return img ** gamma