Replaced ImageMagick by Netpbm for load/save of Netpbm files.

[magister-ludi]

Netpbm.jl has been extended to load and save all netpbm formats. The changes in this PR register Netpbm.jl to perform all load/save operations for these formats.

The default (i.e. without explicit format notation) save operations are the binary formats.

[coveralls]

Coverage remained the same at 73.121% when pulling 22ab488 on magister-ludi:m-l/netpbm into a01dbea on JuliaIO:master.

[IanButterworth]

Just a thought. Might it be worth putting this into ImageIO, beside PNGFiles and the other image loaders that will be added?

That way FileIO will be told to use ImageIO for Netpbm files, and ImageIO will direct to Netpbm.jl ?

There shouldn't be any noticeable overhead. It would just make it easier for users to install image readers in one go. There's even talk of adding ImageIO.jl to Images.jl

[magister-ludi]

That's a sensible suggestion. I'll have a closer look at ImageIO and see what I can do.

[magister-ludi]

I have submitted a PR (JuliaIO/ImageIO.jl#13) to ImageIO that handles Netpbm formats (via Netpbm.jl). If that is merged, I can modify this PR so that FileIO registers ImageIO instead of Netpbm. If somebody else does the modification, that's not a problem for me.

[magister-ludi]

I've updated the registry codeso that ImageIO is used to load and save Netpbm formats.

@ianshmean

[codecov]

Codecov Report

Merging #280 (22ab488) into master (a01dbea) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #280   +/-   ##
=======================================
  Coverage   73.12%   73.12%           
=======================================
  Files           8        8           
  Lines         439      439           
=======================================
  Hits          321      321           
  Misses        118      118           

Impacted Files	Coverage Δ
src/registry.jl	92.64% <ø> (ø)

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[johnnychen94]

Let's still keep ImageMagick, otherwise, it's a breaking change. Similar to other entries.

Suggested change

	add_format(format"PBMBinary", b"P4", ".pbm", [:ImageIO])
	add_format(format"PBMBinary", b"P4", ".pbm", [:ImageIO], [:ImageMagick])

[magister-ludi]

The current version on master has the following entries:

• P4 [:ImageMagick]
• P5 [:Netpbm]
• P6 [:Netpbm]
• P1 [:ImageMagick, LOAD]
• P2 [:ImageMagick, LOAD]
• P3 [:ImageMagick, LOAD]

I can change it to

• P4 [:ImageIO], [:Netpbm], [:ImageMagick]
• P5 [:ImageIO], [:Netpbm]
• P6 [:ImageIO], [:Netpbm]
• P1 [:ImageIO], [:Netpbm], [:ImageMagick, LOAD]
• P2 [:ImageIO], [:Netpbm], [:ImageMagick, LOAD]
• P3 [:ImageIO], [:Netpbm], [:ImageMagick, LOAD]

Then the current options are available as fallback, and Netpbm can be used for all formats if ImageIO is not installed.

[magister-ludi]

I've added these changes.

Thanks @ianshmean and @johnnychen94 for your advice on getting this right.

[IanButterworth]

I think we're good to merge now, but can you confirm with approval please @johnnychen94