ENH: Add DWI volume plot method

Add DWI volume plot method.

nireports/reportlets/modality/dwi.py

@@ -21,10 +21,66 @@
 #     https://www.nipreps.org/community/licensing/
 #
 """Visualizations for diffusion MRI data."""
+import nibabel as nb
 import numpy as np
 from matplotlib import pyplot as plt
 from matplotlib.pyplot import cm
 from mpl_toolkits.mplot3d import art3d
+from nilearn.plotting import plot_anat
+
+
+def plot_dwi(dataobj, affine, gradient=None, **kwargs):
+    """
+    Plot orthogonal (axial, coronal, sagittal) slices of a given DWI volume. The
+    slices displayed are determined by a tuple contained in the ``cut_coords``
+    keyword argument.
+
+    Parameters
+    ----------
+    dataobj : :obj:`numpy.ndarray`
+        DWI volume data: a single 3D volume from a given gradient direction.
+    affine : :obj:`numpy.ndarray`
+        Affine transformation matrix.
+    gradient : :obj:`numpy.ndarray`
+        Gradient values in RAS+b format at the chosen gradient direction.
+    kwargs : :obj:`dict`
+        Extra args given to :obj:`nilearn.plotting.plot_anat()`.
+
+    Returns
+    -------
+    :class:`nilearn.plotting.displays.OrthoSlicer` or None
+        An instance of the OrthoSlicer class. If ``output_file`` is defined,
+        None is returned.
+
+    """
+
+    plt.rcParams.update(
+        {
+            "text.usetex": True,
+            "font.family": "sans-serif",
+            "font.sans-serif": ["Helvetica"],
+        }
+    )
+
+    affine = np.diag(nb.affines.voxel_sizes(affine).tolist() + [1])
+    affine[:3, 3] = -1.0 * (affine[:3, :3] @ ((np.array(dataobj.shape) - 1) * 0.5))
+
+    vmax = kwargs.pop("vmax", None) or np.percentile(dataobj, 98)
+    cut_coords = kwargs.pop("cut_coords", None) or (0, 0, 0)
+
+    return plot_anat(
+        nb.Nifti1Image(dataobj, affine, None),
+        vmax=vmax,
+        cut_coords=cut_coords,
+        title=(
+            r"Reference $b$=0"
+            if gradient is None
+            else f"""\
+$b$={gradient[3].astype(int)}, \
+$\\vec{{b}}$ = ({', '.join(str(v) for v in gradient[:3])})"""
+        ),
+        **kwargs,
+    )
 
 
 def plot_heatmap(

nireports/tests/test_dwi.py

@@ -23,11 +23,38 @@
 """Test DWI reportlets."""
 
 import pytest
+from pathlib import Path
 
+import nibabel as nb
 import numpy as np
 from matplotlib import pyplot as plt
 
-from nireports.reportlets.modality.dwi import plot_gradients
+from nireports.reportlets.modality.dwi import plot_dwi, plot_gradients
+
+
+@pytest.mark.parametrize(
+    'dwi', 'dwi_btable',
+    ['ds000114_sub-01_ses-test_dwi.nii.gz', 'ds000114_singleshell'],
+)
+def test_plot_dwi(tmp_path, testdata_path, dwi, dwi_btable, outdir):
+    """Check the plot of DWI data."""
+
+    dwi_img = nb.load(testdata_path / f'{dwi}')
+    affine = dwi_img.affine
+
+    bvecs = np.loadtxt(testdata_path / f'{dwi_btable}.bvec').T
+    bvals = np.loadtxt(testdata_path / f'{dwi_btable}.bval')
+
+    gradients = np.hstack([bvecs, bvals[:, None]])
+
+    # Pick a random volume to show
+    rng = np.random.default_rng(1234)
+    idx = rng.integers(low=0, high=len(bvals), size=1).item()
+
+    _ = plot_dwi(dwi_img.get_fdata()[..., idx], affine, gradient=gradients[idx])
+
+    if outdir is not None:
+        plt.savefig(outdir / f'{Path(dwi).with_suffix("").stem}.svg', bbox_inches='tight')
 
 
 @pytest.mark.parametrize(