add brightness_contrast function

[aquatiko]

A handy function to visualize your fits images by changing brightness and contrast in your Jupyter notebooks. Currently works for GrayScale images.

• [X] Add brightness_contrast function

• [X] Update Docs

• [x] Tweak to accept range from user (brightness and contrast)

Results in IJulia:

[aquatiko]

https://docs.opencv.org/3.4/d3/dc1/tutorial_basic_linear_transform.html Reference for changing brightness and contrast using operation g(x) = a*f(x) + b where a controls contrast and b brightness Also, I have added a threshold parameter to filter out pixels below it.

[aquatiko]

@giordano I have added the required changes but I don't quite understand the feature going to showmime.jl step.

[coveralls]

Pull Request Test Coverage Report for Build 35

• 3 of 4 (75.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+9.5%) to 95.238%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/showmime.jl	3	4	75.0%
<!--	Total:	3	4	75.0%	-->

Totals
Change from base Build 20:	9.5%
Covered Lines:	20
Relevant Lines:	21

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💛 - Coveralls

[codecov-io]

Codecov Report

Merging #7 into master will increase coverage by 0.21%. The diff coverage is 75%.

@@            Coverage Diff             @@
##           master       #7      +/-   ##
==========================================
+ Coverage   97.22%   97.43%   +0.21%     
==========================================
  Files           3        3              
  Lines          36       39       +3     
==========================================
+ Hits           35       38       +3     
  Misses          1        1

Impacted Files	Coverage Δ
src/AstroImages.jl	100% <ø> (ø)	:arrow_up:
src/showmime.jl	75% <75%> (+75%)	:arrow_up:

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[giordano]

Please, also add a test for this function. A @testset on its own is fine.

In general, it is very important to test every feature you introduce, or bug you fix.

[aquatiko]

@giordano the function visualize just shows the slider interface in IJulia. What should one assert for the tests? Also, can you give some pointers on steps for showmime.jl

[giordano]

Don't worry about using it in showmime, it's trickier than I expected, I need to think more about it. I'll also the test.

[aquatiko]

@giordano would this require any more work before getting merged?

[giordano]

would this require any more work before getting merged?

Not from you, thanks!

I'm waiting for an answer to this question: https://discourse.julialang.org/t/base-show-method-for-showing-a-widget-in-jupyter/22099 I initially thought that simply replacing the render function with the new function in https://github.com/JuliaAstro/AstroImages.jl/blob/282b59e70ec522061f5bc39710c89f3df6adbe50/src/showmime.jl#L2-L3 would have been sufficient. It turned out that this isn't the case, we probably need to use another MIME, but I don't know which one.

[giordano]

The trick is to use text/html: https://discourse.julialang.org/t/base-show-method-for-showing-a-widget-in-jupyter/22099/4 Would you like to have the honour to do the change? :slightly_smiling_face:

[aquatiko]

Yeah sure!! It would help me learn about the Jupyter interface we would be doing later

[aquatiko]

@giordano Would this require further work before merging?

[aquatiko]

@giordano I think this needs a CI re-run.