specialize imrotate for 0, 90, 180, 270 degrees

[johnnychen94]

img = testimage("cameraman") # (512, 512)

# Before: (514, 514)
# After: (512, 512)
size(imrotate(img, pi/2))

# Before: sizes are not equal
# After: true
imrotate(imrotate(imrotate(imrotate(img, pi/2), pi/2), pi/2), pi/2) == img

# Before: sizes are not equal
# After: true
imrotate(imrotate(img, pi), pi) == img

[codecov[bot]]

Codecov Report

Merging #79 into master will increase coverage by 0.56%. The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #79      +/-   ##
==========================================
+ Coverage   88.56%   89.12%   +0.56%     
==========================================
  Files           7        7              
  Lines         271      285      +14     
==========================================
+ Hits          240      254      +14     
  Misses         31       31

Impacted Files	Coverage Δ
src/warp.jl	100% <100%> (ø)	:arrow_up:

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[johnnychen94]

I believe this PR is ready for review and merge

[Evizero]

is it type stable? was it before this PR?

[johnnychen94]

Thanks for the comment, I'm already aware of the type stability issue, I'll come back and try to fix that later when I finished the upgrading of Augmentor.jl made by @Evizero (for my own research interest)

[kimikage]

BTW, 360 ° seems to be missing.

[kimikage]

BTW, I think it is better to round the rotation matrix instead of quantizing the angle.

[johnnychen94]

That sounds promising to me!

[mkitti]

It seems a bit dangerous to specialize on an approximation for an irrational number. Maybe it would be better to have a degree based version of imrotate and specialize on multiples of 90 like the title suggests? The discretized imrotate could then map to that.

Otherwise, I would really appreciate something like this. It's absence was duly noted when attempting something AoC2020 Day 20: https://adventofcode.com/2020/day/20

[mkitti]

sinpi and cospi could also have some relevance here. https://docs.julialang.org/en/v1/base/math/#Base.Math.sinpi

[timholy]

I'll let @johnnychen94 decide what to do here, but I put all the tests from this PR into #149 and they pass.