Improve section savefig/png in chapter output in file output.md

[t37w]

The documentation of section "savefig/png" should be improved to reflect the information available in the source code, for example as comments and real examples. Good for a better learning curve of newcomers.

• list of supported output formats also with same note from source "not all backends support every format"
• which output formats are supported by every backend
• default output format

In addition, some information about the resolution used in the output format. I created some png files for my package using gr() backend. They all had a resolution of 3600 x 2400 pixels which is ways too large.
Being able to define the wanted resolution would be great and could reduce / simplify the related workflow.

[mkborregaard]

Good ideas.
A little weird with the super high resolution in GR - I think that may be something new.

[mkborregaard]

You can use size to define the size of the plot in pixels.

[t37w]

Thank you for the hint.
I think you mean, one can write (a complete example to be reproducable)

using Plots;gr() # default window size
x=rand(101); y=rand(101)+10; z=rand(101)+100;
foo=plot(x,y,z,size=(450,300))
png(foo,"Try_save_small_png_v003_plot(x,y,z,size=(450,300))")

The problem is, the appropriate function does an upscaling by a factor of 6 for each axis in the png file. This currently means one has to plot into a "stamp" resulting in not nice graphics.
Maybe this was / is correct for the one or the other backend or is an artifact now.
Or do have another syntax in mind?

Cheers,
Thomas

[mkborregaard]

@jheinen is this expected with GR?

[t37w]

As addendum to the high resolution of png files. according to the table
http://docs.juliaplots.org/latest/supported/#keyword-arguments
the backend 'gr' does not support the keyword 'dpi'. Could this be one reason ?

[t37w]

After some more and deeper investigations, the gr-backend reacts on the plot attribute dpi, example:

foo=plot(x,y,z,dpi=300)
png(foo,"Try_save_small_png_v004_plot(x,y,z,dpi=300))")

This results in a png-file which is 3 times larger for each size parameter.
AFAIK, the scaling should make the width and height smaller.

[t37w]

Proposal of an extended section of 'savefig' in file 'outpout.md'

I have no experience with pull requests, ... as I'm new to github and the related workflow.
In a fork of PlotDocs I have extended the section about 'savefig' in file 'output.md'. Please see
https://github.com/t37w/PlotDocs.jl/blob/t37w_output_savefig/docs/src/output.md

Cheers,
Thomas

[mkborregaard]

That looks sensible. It's easier to give feedback if you do a pull request. You can do that here on github by going to JuliaPlots/PlotDocs, clicking "new pull request" then "compare across forks"