Add --inpaint-alpha to CLI and API changes to derive mask from channels

[khskarl]

Hey, found myself in a Hacktoberfest event this Saturday and it felt like a good opportunity to try my hand on #22 :).

Changes

To derive an inpaint mask from the alpha channel I felt it would be more "idiomatic" according to the lib to do some changes on ImageSource, therefore there are some minor modifications on it.

• Adds boolean --inpaint-alpha argument to CLI
• New Mask enum
• The original ImageSource is now DataSource
• ImageSource is now a struct with a Mask and a DataSource

Usage

texture-synthesis --out=result.png --inpaint-alpha generate silly_example_with_alpha.png

Example

Example:

Result:

(Image source: https://unsplash.com)

Checklist

• Run tests locally
• Run all examples locally
• Run rustfmt
• Run clippy

[Jake-Shadle]

Hey, thanks for the PR! I've left some comments. 🙂

[Jake-Shadle]

I realise #22 specifically mentions the alpha channel, but might want to just name this --inpaint-channel <r, g, b, a> instead (defaulting to alpha) since you already added support for different mask channels.

[khskarl]

Not very experienced with structupt, does it support a way to set the default value only if the flag is present?
E.g.
texture-synthesis --inpaint-channel will be texture-synthesis --inpaint-channel=a
texture-synthesis won't be texture-synthesis --inpaint-channel=a

[Jake-Shadle]

This should just take image by &mut, as now there is an unnecessary copy made that gets immediately discarded at the one call site.

[Jake-Shadle]

ImageSource already has From<AsRef<Path>> that does this.

[Jake-Shadle]

--inpaint and --inpaint-channel should probably be exclusive, structopt doesn't really support that atm, so you can just check manually and error if they are both set.

[khskarl]

Just finished most of the changes, but I ran into lifetime issues when trying to do ImageSource::from as in:

path => example.set_sample_method(SampleMethod::Image(ImageSource::from(
                    &std::path::Path::new(path),
                ))),

---

Error message:

error[E0716]: temporary value dropped while borrowed
   --> cli/src/main.rs:238:22
    |
229 |             if i == examples.len() {
    |                     -------- borrow later used here
...
238 |                     &std::path::Path::new(path),
    |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^ creates a temporary which is freed while still in use
239 |                 ))),
    |                   - temporary value is freed at the end of this statement
    |
    = note: consider using a `let` binding to create a longer lived value

I don't have a good grasp on lifetimes, so I will have to dig into that later as I have to get back to my thesis for now.

[Jake-Shadle]

Thanks for adding this feature!

[Jake-Shadle]

Closing this in favor of #67 which has all the changes and does some minor cleanup, again, thanks so much for this PR, really sorry it took so long!

[khskarl]

No problem, happy to contribute :).