diff --git a/colorhash/__main__.py b/colorhash/__main__.py
index 81b8a82..56dee97 100644
--- a/colorhash/__main__.py
+++ b/colorhash/__main__.py
@@ -154,13 +154,6 @@ def main() -> None:
         case _:
             assert False, f"unknown input type {args.input_type}"
 
-    # Choose the palette
-    palette: list[str]
-    if args.palette == "auto":
-        palette = list(DEFAULT_PALETTES.values())[sum(hashdata) % len(DEFAULT_PALETTES)]
-    else:
-        palette = PALETTES[args.palette]
-
     # Choose the dimensions and the matricizer
     matricizer: Matricizer
     match args.matrix:
@@ -170,10 +163,17 @@ def main() -> None:
         case "randomart":
             # 17x9 is what openssh uses
             # TODO - allow configuring dimensions, maybe
-            matricizer = RandomartMatricizer(17, 9)
+            matricizer = RandomartMatricizer(11, 6)
         case _:
             assert False, f"invalid args.matrix: {args.matrix}"
 
+    # Choose the palette
+    palette: list[str]
+    if args.palette == "auto":
+        palette = matricizer.choose_palette(hashdata, PALETTES)
+    else:
+        palette = PALETTES[args.palette]
+
     # Choose the colorizer
     colorizer = PaletteColorizer(palette)
 
diff --git a/colorhash/matricizer.py b/colorhash/matricizer.py
index 657503c..111e758 100644
--- a/colorhash/matricizer.py
+++ b/colorhash/matricizer.py
@@ -1,6 +1,8 @@
 "All things that turn a hash into a matrix."
 import abc
-from typing import Sequence
+from typing import Mapping, Sequence
+
+from .palettes import Palette, DEFAULT_PALETTES
 
 
 Matrix = Sequence[Sequence[int]]
@@ -33,6 +35,12 @@ class Matricizer(metaclass=abc.ABCMeta):
         :returns: the matrix converted from the hash data.
         """
 
+    @abc.abstractmethod
+    def choose_palette(self, data: bytes, palettes: Mapping[str, Palette]) -> Palette:
+        """
+        Choose a palette based on the give data and palettes.
+        """
+
 
 class NibbleMatricizer(Matricizer):
     """
@@ -81,6 +89,9 @@ class NibbleMatricizer(Matricizer):
 
         return cols
 
+    def choose_palette(self, data: bytes, palettes: Mapping[str, Palette]) -> Palette:
+        return list(palettes.values())[sum(data) % len(palettes)]
+
 
 class RandomartMatricizer(Matricizer):
     """
@@ -127,3 +138,6 @@ class RandomartMatricizer(Matricizer):
                 if rows[r][c] < 0xF:
                     rows[r][c] += 1
         return rows
+
+    def choose_palette(self, _data: bytes, _palettes: Mapping[str, Palette]) -> Palette:
+        return DEFAULT_PALETTES['rainbow']