add imageplot (support sixel)

[t-bltg]

Fix #153, goes with JuliaPlots/Plots.jl#4011.

with Sixel ¹

using Sixel, UnicodePlots, ImageInTerminal, TestImages, ImageTransformations

main() = begin
  img = imresize(testimage("mandril_color"), ratio=.4)
  display(UnicodePlots.image(img, title="mandril sixel"))
  return
end

main()

without Sixel

using UnicodePlots, ImageInTerminal, TestImages, ImageTransformations

main() = begin
  img = imresize(testimage("mandril_color"), ratio=.4)
  ImageInTerminal.use_24bit()
  display(UnicodePlots.image(img, title="mandril 24 bit"))
  ImageInTerminal.use_256()
  display(UnicodePlots.image(img, title="mandril 256 color"))
  return
end

main()

Discussion:

• naming ?, should we export this ? chose to unexport image
• img is downsized using restrict in ImageInTerminal, is there a solution to get the ratio so that we can add a centered title and/or labels ? solved using terminal control sequences to query the cursor carret size
• is the approach using @require standard, for optional dependency ImageInTerminal, or should we instead add ImageInTerminal as a hard dependency ?
• the sixel implementation was tricky, had to use some ansi escape codes for printing the right border, maybe we can do something better (see the following mwe for writing after a sixel sequence)

$ printf '\ePq
#0;2;0;0;0#1;2;100;100;0#2;2;0;100;0
#1~~@@vv@@~~@@~~$
#2??}}GG}}??}}??-
#1!14@\e\\\e[A\e[2Cworld
'

Footnotes

1. for sixel support, code snippet must be ran under a compatible terminal. ↩

[codecov-commenter]

Codecov Report

Base: 99.94% // Head: 99.14% // Decreases project coverage by -0.79% ⚠️

Coverage data is based on head (db0a707) compared to base (cf9be69).
Patch coverage: 75.86% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #196      +/-   ##
==========================================
- Coverage   99.94%   99.14%   -0.80%     
==========================================
  Files          29       31       +2     
  Lines        1716     1755      +39     
==========================================
+ Hits         1715     1740      +25     
- Misses          1       15      +14     

Impacted Files	Coverage Δ
src/UnicodePlots.jl	100.00% <ø> (ø)
src/graphics/imagegraphics.jl	65.62% <65.62%> (ø)
src/common.jl	99.09% <66.66%> (-0.45%)	⬇️
src/show.jl	99.20% <88.88%> (-0.80%)	⬇️
src/canvas/densitycanvas.jl	100.00% <100.00%> (ø)
src/graphics.jl	100.00% <100.00%> (ø)
src/graphics/bargraphics.jl	100.00% <100.00%> (ø)

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[johnnychen94]

I hope we can pend this PR for a while until we address JuliaImages/ImageInTerminal.jl#48. The current ImageInTerminal has one unwanted side effect; that any package loads ImageInTerminal would change how colorant arrays are rendered in terminal even if you don't call it with UnicodePlots.image because it overrides Base.show.

[t-bltg]

I hope we can pend this PR for a while until we address JuliaImages/ImageInTerminal.jl#48.

Thanks, for pointing that. Maybe I can help on that matter ?

The current ImageInTerminal has one unwanted side effect; that any package loads ImageInTerminal would change how colorant arrays are rendered in terminal even if you don't call it with UnicodePlots.image because it overrides Base.show.

Is this something we want to change for ImageInTerminal 1.0 ?

[johnnychen94]

Is this something we want to change for ImageInTerminal 1.0 ?

Yes, I'd like to separate ImageInTerminal into two packages: backends and frontends. The backend might be as simple as ascii_encode(img) and the frontend would provide a Display type and override Base.display and Base.show method. For instance, Sixel.jl can be seen as an ImageInTerminal backend.

To do this, we need to rework and deprecate the current imshow implementation: 1) introduces a pure encoding backend ascii_encode([io], img, method; kwargs...) as I did in Sixel.jl, make it a standalone package (say AsciiImageEncoding, a bad package name, but you can get the point), and 2) introduce a TerminalGraphicDisplay type in the frontend package ImageInTerminal.

By doing this, this PR can directly use the ascii_encode methods in the new backend package just like using sixel_encode in Sixel. We could also move some core encoding functionality of the UnicodePlots to the new backend package. I believe this provides better flexibility in reusing the codes.

[johnnychen94]

Thanks, for pointing that. Maybe I can help on that matter ?

Yeah, given that I have too many items on my todo-list it would be great if you can help implement this! I just sent you an invitation to ImageInTerminal, you can choose to implement the backend package in it as a sub-package like SnoopCompileCore, or you can create a new package and refactor the encoding part of ImageInTerminal to the new package.

[t-bltg]

Thanks, I'll continue the discussion in JuliaImages/ImageInTerminal.jl#52 about details.

[t-bltg]

I will probably merge this in the next few days, unless objection(s).
The usage is a bit marginal with Sixels, but my usage of it atm is fine.