new demo: block-by-block visualization as GIF

Project.toml

@@ -59,7 +59,7 @@ ImageMorphology = "0.2"
 ImageSegmentation = "1"
 ImageShow = "0"
 ImageTransformations = "0"
-Images = "0.23"
+Images = "0.24"
 IndirectArrays = "0"
 MappedArrays = "0"
 MosaicViews = "0"

docs/examples/visualization/block_visualization.jl

@@ -0,0 +1,64 @@
+# ---
+# title: Block-by-Block Visualization
+# description: This demo shows you how to create a block-by-block image visualization.
+# cover: assets/block_visualization.gif
+# author: Johnny Chen
+# date: 2021-05-05
+# ---
+
+using Images
+using PaddedViews, OffsetArrays
+using TestImages
+using ImageBinarization
+
+# !!! tip
+#     It is recommended to read the demo [Layer Compositing](@ref Layer-Compositing) first to get an idea
+#     of how [OffsetArrays.jl](https://github.com/JuliaArrays/OffsetArrays.jl) and
+#     [PaddedViews.jl](https://github.com/JuliaArrays/PaddedViews.jl) can be used to simplify the
+#     canvas/axes organization.
+
+img = imresize(testimage("lighthouse"), ratio=0.5)
+img₀₁ = binarize(img, AdaptiveThreshold())
+
+# As you may have seen in other demos, the simplest way to compare multiple images is to use `mosaic`:
+
+mosaic(img, img₀₁; nrow=1)
+
+# In this demo, we will use `Images.gif` to create something different by adding a "time" axis. As
+# an example, we use `TiledIteration` to move our focus on a block/patch/tile level.
+
+using TiledIteration
+tile_indices = TileIterator(axes(img), (32, 32))[:]
+tiles = [img[R...] for R in tile_indices]
+## visualize the tiles at fps rate 5, i.e., 5 frames per second.
+Images.gif(tiles; fps=5)
+
+# This is not very meaningful as it simply stacks all tiles together, so next we'll add
+# back the axes information for each block. We also use the original image as the
+# background.
+
+function create_frames(img, background, tile_indices; rf=0.8, rb=1-rf)
+    map(tile_indices) do R
+        ## add back axes information to given blcok
+        block = OffsetArray(img[R...], OffsetArrays.Origin(first.(R)))
+        canvas, block = paddedviews(zero(eltype(background)), background, block)
+        frame = clamp01!(@. rb*canvas .+ rf*block)
+    end
+end
+
+frames = create_frames(img, img, tile_indices)
+Images.gif(frames; fps=5)
+
+# Now, instead of using `mosaic`, we use this to compare our images.
+
+frames = create_frames(img₀₁, img, tile_indices; rb=0.4)
+Images.gif(frames; fps=5)
+
+# This may not be the best way to visually compare these two images, but you get the
+# idea of how to add back axes information to each block, and visualize it as an animated
+# GIF.
+
+# make cover image #src
+tile_indices = TileIterator(axes(img), (48, 48))[:] #src
+frames = create_frames(img₀₁, img, tile_indices; rb=0.4) #src
+save("assets/block_visualization.gif", Images.gif(frames); fps=2) #src