allow custom processor through init

[drkibitz]

• This allows shared custom processors to be provided rather than depending only on factory methods of image requests

e.g.

let imageRequest = ImageRequest(url: url, processor: MyProccessor.shared)

I also added tests for this and my previous pull request for upscaling.

[kean]

Hey, @drkibitz! Thanks, I think it makes sense to add a convenience initializer like that.

I would suggest making this init generic to hide AnyImageProcessor (it exists because of the Swift limitations):

public init<Processor: ImageProcessing>(urlRequest: URLRequest, processor: Processor) {
        self = ImageRequest(urlRequest: urlRequest)
        self.processor = AnyImageProcessor(processor)
 }

[kean]

// Convenience initializers with custom processer. The reason
// why those are implemented as separate init methods is to take advantage
// of memorized `decompressor` when custom parameters are not needed.

I'm not sure I follow, could you please clarify what you meant by this comment? I don't see how these new initializes allow you to do something that the existing ones don't.

[drkibitz]

@kean That comment was taken from what was already there, changing "Convenience initializers with targetSize and contentMode." to "Convenience initializers with custom processer.". I didn't mean anything by the comment other than just trying to repeat the pattern of the previous comment but for the custom processor parameter.

[drkibitz]

@kean Out of curiosity, what are you gaining by making the image processor objects in this library structs?

[drkibitz]

@kean also, FYI, I've updated the PR hopefully to your liking. I've taken a little liberty on the comment(s), and the init calling pattern.

[kean]

Oh, right, there is an existing comment like that 😄. I will take a look, not sure why I thought it was necessary, seems outdated. It's there just for convenience and to make API for resizing images - which is a common operation - easier to find and use.

Out of curiosity, what are you gaining by making the image processor objects in this library structs?

AFAIR to reduce the number of allocations and deallocations, that's it.