diff --git a/dmriprep/utils/register.py b/dmriprep/utils/register.py
new file mode 100644
index 00000000..7e6ecd3b
--- /dev/null
+++ b/dmriprep/utils/register.py
@@ -0,0 +1,189 @@
+"""
+Linear affine registration tools for motion correction.
+"""
+import attr
+
+import numpy as np
+import nibabel as nb
+from dipy.align.metrics import CCMetric, EMMetric, SSDMetric
+
+from dipy.align.imaffine import (
+    transform_centers_of_mass,
+    AffineMap,
+    MutualInformationMetric,
+    AffineRegistration,
+)
+
+from dipy.align.transforms import (
+    TranslationTransform3D,
+    RigidTransform3D,
+    AffineTransform3D,
+)
+from nipype.utils.filemanip import fname_presuffix
+
+syn_metric_dict = {"CC": CCMetric, "EM": EMMetric, "SSD": SSDMetric}
+
+
+__all__ = [
+    "c_of_mass",
+    "translation",
+    "rigid",
+    "affine",
+    "AffineRegistration",
+]
+
+
+def apply_affine(moving, static, transform_affine, invert=False):
+    """Apply an affine to transform an image from one space to another.
+
+    Parameters
+    ----------
+    moving : array
+       The image to be resampled
+
+    static : array
+
+    Returns
+    -------
+    warped_img : the moving array warped into the static array's space.
+
+    """
+    affine_map = AffineMap(
+        transform_affine, static.shape, static.affine, moving.shape, moving.affine
+    )
+    if invert is True:
+        warped_arr = affine_map.transform_inverse(np.asarray(moving.dataobj))
+    else:
+        warped_arr = affine_map.transform(np.asarray(moving.dataobj))
+
+    return nb.Nifti1Image(warped_arr, static.affine)
+
+
+def average_affines(transforms):
+    affine_list = [np.load(aff) for aff in transforms]
+    average_affine_file = fname_presuffix(
+        transforms[0], use_ext=False, suffix="_average.npy"
+    )
+    np.save(average_affine_file, np.mean(affine_list, axis=0))
+    return average_affine_file
+
+
+# Affine registration pipeline:
+affine_metric_dict = {"MI": MutualInformationMetric, "CC": CCMetric}
+
+
+def c_of_mass(
+    moving, static, static_affine, moving_affine, reg, starting_affine, params0=None
+):
+    transform = transform_centers_of_mass(static, static_affine, moving, moving_affine)
+    transformed = transform.transform(moving)
+    return transform
+
+
+def translation(
+    moving, static, static_affine, moving_affine, reg, starting_affine, params0=None
+):
+    transform = TranslationTransform3D()
+    translation = reg.optimize(
+        static,
+        moving,
+        transform,
+        params0,
+        static_affine,
+        moving_affine,
+        starting_affine=starting_affine,
+    )
+
+    return translation
+
+
+def rigid(
+    moving, static, static_affine, moving_affine, reg, starting_affine, params0=None
+):
+    transform = RigidTransform3D()
+    rigid = reg.optimize(
+        static,
+        moving,
+        transform,
+        params0,
+        static_affine,
+        moving_affine,
+        starting_affine=starting_affine,
+    )
+    return rigid
+
+
+def affine(moving, static, static_affine, moving_affine, reg, starting_affine,
+           params0=None):
+    """
+    """
+    transform = AffineTransform3D()
+    affine = reg.optimize(
+        static,
+        moving,
+        transform,
+        params0,
+        static_affine,
+        moving_affine,
+        starting_affine=starting_affine,
+    )
+
+    return affine
+
+
+@attr.s(slots=True, frozen=True)
+class AffineRegistration():
+    def __init__(self):
+        nbins = attr.ib(default=32)
+        sampling_prop = attr.ib(default=1.0)
+        metric = attr.ib(default="MI")
+        level_iters = attr.ib(default=[10000, 1000, 100])
+        sigmas = attr.ib(defaults=[3, 1, 0.0])
+        factors = attr.ib(defaults=[4, 2, 1])
+        pipeline = attr.ib(defaults=[c_of_mass, translation, rigid, affine])
+
+    def fit(self, static, moving, params0=None):
+        """
+        static, moving : nib.Nifti1Image class images
+        """
+        if params0 is None:
+            starting_affine = np.eye(4)
+        else:
+            starting_affine = params0
+
+        use_metric = affine_metric_dict[self.metric](self.nbins,
+                                                     self.sampling_prop)
+        affreg = AffineRegistration(
+            metric=use_metric,
+            level_iters=self.level_iters,
+            sigmas=self.sigmas,
+            factors=self.factors)
+
+        # Go through the selected transformation:
+        for func in self.pipeline:
+            transform = func(
+                np.asarray(moving.dataobj),
+                np.asarray(static.dataobj),
+                static.affine,
+                moving.affine,
+                affreg,
+                starting_affine,
+                params0,
+            )
+            starting_affine = transform.affine
+
+        self.static_affine_ = static.affine
+        self.moving_affine_ = moving.affine
+        self.affine_ = starting_affine
+        self.reg_ = AffineMap(starting_affine,
+                              static.shape, static.affine,
+                              moving.shape, moving.affine)
+
+    def apply(self, moving):
+        """
+
+        """
+        data = moving.get_fdata()
+        assert np.all(moving.affine, self.moving_affine_)
+        return nb.Nifti1Image(np.array(self.reg_.transform(data)),
+                              self.static_affine_)
diff --git a/setup.cfg b/setup.cfg
index 61b04423..a9be9d6f 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -26,6 +26,7 @@ install_requires =
     nibabel ~= 3.0
     nipype ~= 1.4
     niworkflows @ git+https://github.com/nipreps/niworkflows.git@master
+    nitransforms
     numpy
     pybids >=0.10.2
     pyyaml