added tests and solved issues in pull request

src/seaborn_image/_grid.py

@@ -367,13 +367,8 @@ def __init__(
                     )
 
             if aspect == "auto":
-                aspect = 1e10
-
-                # Select minimum aspect ratio among all the images
-                for img in data:
-                    aspect_aux = img.shape[1] / img.shape[0]
-                    if aspect_aux < aspect:
-                        aspect = aspect_aux
+                aspect_ratios = [img.shape[1] / img.shape[0] for img in data]
+                aspect = min(aspect_ratios)
 
         elif not isinstance(data, np.ndarray):
             raise ValueError("image data must be a list of images or a 3d or 4d array.")
@@ -433,7 +428,7 @@ def __init__(
 
             if aspect == "auto":
                 # Select axis where width and height are
-                height_idx, width_idx = [i for i in range(data.ndim) if i != axis][:2]
+                height_idx, width_idx = [i for i in range(data.ndim) if i != (axis % data.ndim)][:2]
 
                 aspect = data.shape[width_idx] / data.shape[height_idx]
 
@@ -1192,10 +1187,10 @@ def __init__(
             ncol = col_wrap
             nrow = int(np.ceil(len(kwargs[f"{col}"]) / col_wrap))
 
-        # Calculate the base figure size
         if aspect == "auto":
             aspect = data.shape[1]/data.shape[0]
-
+
+        # Calculate the base figure size
         figsize = (ncol * height * aspect, nrow * height)
 
         fig = plt.figure(figsize=figsize)

tests/test_grid.py

@@ -871,7 +871,28 @@ def test_figure_size(self):
         )
         np.testing.assert_array_equal(g4.fig.get_size_inches(), (3 * 2 * 1.5, 2 * 2))
         plt.close()
+
+    def test_auto_aspect(self):
+        imgsize0 = (10, 10)
+        g0 = isns.ImageGrid([np.zeros(imgsize0) for i in range(10)], aspect='auto')
+        assert np.isclose(imgsize0[1]/imgsize0[0], g0.aspect)
+        plt.close()
 
+        imgsize1 = (10, 5)
+        g1 = isns.ImageGrid([np.zeros(imgsize1) for i in range(10)], aspect='auto')
+        assert np.isclose(imgsize1[1]/imgsize1[0], g1.aspect)
+        plt.close()
+
+        imgsize2 = (5, 10)
+        g2 = isns.ImageGrid([np.zeros(imgsize2) for i in range(10)], aspect='auto')
+        assert np.isclose(imgsize2[1]/imgsize2[0], g2.aspect)
+        plt.close()
+
+        imglist = [np.zeros(imgsize0) for i in range(4)] + [np.zeros(imgsize1) for i in range(4)] + [np.zeros(imgsize2) for i in range(4)]
+        g3 = isns.ImageGrid(imglist, aspect='auto')
+        assert np.isclose(min([imgsize0[1]/imgsize0[0], imgsize1[1]/imgsize1[0], imgsize2[1]/imgsize2[0]]), g3.aspect)
+        plt.close()
+
     def test_vmin_vmax(self):
         g = isns.ImageGrid(cells, vmin=0.5, vmax=0.75)
         for ax in g.axes.ravel():