docs: introduce MosaicViews as dataset preview utils

Author: johnnychen94

docs/Project.toml

@@ -1,2 +1,5 @@
 [deps]
 Documenter = "e30172f5-a6a5-5a46-863b-614d45cd2de4"
+ImageCore = "a09fc81d-aa75-5fe9-8630-4744c3626534"
+ImageIO = "82e4d734-157c-48bb-816b-45c225c6df19"
+ImageShow = "4e3cecfd-b093-5904-9786-8bbb286a6a31"

docs/src/index.md

@@ -55,3 +55,22 @@ will trigger a download dialog to `~/.julia/datadeps/MNIST`. To
 overwrite this on a case by case basis, it is possible to specify
 a data directory directly in `traindata(dir = <directory>)` and
 `testdata(dir = <directory>)`.
+
+## Preview
+
+For image dataset, [`MosaicViews`](https://github.com/JuliaArrays/MosaicViews.jl) provides a very simple interface to display a list
+of images.
+
+```@example
+using MLDatasets
+# Alternatively, you can also just call `using Images`
+using ImageCore, ImageShow
+
+# The original dataset is stored in row-major order,
+# to display it normally in Julia, we need to permute the
+# first two dimensions.
+test_x = Gray.(PermutedDimsArray(MNIST.testtensor(), (2, 1, 3)));
+test_x_sample = @view test_x[:, :, 1:64];
+
+mosaic(test_x_sample, nrow=8)
+```