Add EMNIST clarification on image orientation.

PiperOrigin-RevId: 265939107

tensorflow_datasets/image/mnist.py

@@ -317,7 +317,11 @@ def _info(self):
             "The EMNIST dataset is a set of handwritten character digits "
             "derived from the NIST Special Database 19 and converted to "
             "a 28x28 pixel image format and dataset structure that directly "
-            "matches the MNIST dataset."),
+            "matches the MNIST dataset.\n\n"
+            "Note: Like the original EMNIST data, images provided here are "
+            "inverted horizontally and rotated 90 anti-clockwise. You can use "
+            "`tf.transpose` within `ds.map` to convert the images to a "
+            "human-friendlier format."),
         features=tfds.features.FeaturesDict({
             "image":
                 tfds.features.Image(shape=MNIST_IMAGE_SHAPE),