reexport MosaicViews

[johnnychen94]

Moved from JuliaImages/ImageShow.jl#19 here so that other image view packages (e.g., ImageView, Plots) can also benefit from this.

In short, this introduces mosaicview as an enhanced version of cat to make the image displaying tasks easier.

Here're two main usages:

1. Compare images of different sizes and colorants (not necessarily two images)

using ImageCore, ImageShow, TestImages
using ColorVectorSpace # this is required for `zero(RGB)`

lena = testimage("lena") # 256*256 RGB image
cameraman = testimage("cameraman") # 512*512 Gray image
mosaicview(lena, cameraman; nrow=1)

2. give a nice looking 2d view for higher-dimensional image (or images)

using ImageCore, ImageShow, TestImages
img = testimage("mri") # 226×186×27

mosaicview(img; fillvalue=0.5, npad=2, ncol=7, rowmajor=true)

closes JuliaImages/ImageShow.jl#19

[codecov]

Codecov Report

Merging #127 into master will not change coverage by %.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #127   +/-   ##
=======================================
  Coverage   60.50%   60.50%           
=======================================
  Files           9        9           
  Lines         400      400           
=======================================
  Hits          242      242           
  Misses        158      158           

Impacted Files	Coverage Δ
src/ImageCore.jl	56.00% <ø> (ø)

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