Revery: Opacity doesn't work on images

[JulesGuesnon]

Hello ! I cloned the last version of the revery-quickstart and the opacity on images seems broken. All of this codes doesn't work:

<Image ... opacity=0.1 />

```reason

```reason
<Opacity opacity=0.1>
    <View>
        <Image ... opacity=0.1 />
    <View>
</Opacity>

[lessp]

As you mentioned in Discord:

I checked github and Image is made with the ppx nativeComponent and under the hood it's an ImageNode object which use Revery_Draw.CanvasContext so I guess it's backed by Skia
But it seems like the opacity is never passed to the context, probably explain why it doesn't work

Here's a basic skia-example with alpha: https://fiddle.skia.org/c/fb3358907fe866eff8f89e0ea13fb056

It seems as our drawImage-method does not take paint as an argument:

https://github.com/revery-ui/revery/blob/395ed2ed531ddc9c8632cb299067e6ce8b87cf43/src/UI/ImageNode.re#L31-L37

My guess would be that we'd have to extend that to perhaps take an option(Paint.t), similar to drawPath:
https://github.com/revery-ui/revery/blob/ced2dde461c316178d4ce320b862a1c9d46a96a6/src/Draw/CanvasContext.re#L141-L143

https://github.com/revery-ui/revery/blob/ced2dde461c316178d4ce320b862a1c9d46a96a6/src/Draw/CanvasContext.re#L165-L178

It also seems as the reason-skia doesn't have bindings for setAlpha/setAlphaf yet.

https://github.com/revery-ui/reason-skia/blob/master/src/Skia.rei#L101-L122

[JulesGuesnon]

I was looking on how to make a binding on reason-skia to setAlpha/setAlphaf and then make a PR, but the fact is that this 2 functions aren't is the Skia c api. Sadly no sk_paint_set_alpha/sk_paint_set_alphaf here.
So I'm exploring how to do it with the color instead

[JulesGuesnon]

I achieved to make a setAlpha for reason-skia 😄 (see the PR above)
So I'm waiting for validations, and if it's merged I can work on a PR to fix this on Revery

[lessp]

I achieved to make a setAlpha for reason-skia 😄 (see the PR above)
So I'm waiting for validations, and if it's merged I can work on a PR to fix this on Revery

Cool, thank you @JulesGuesnon!

EDIT: You can always point Revery to use your PR of reason-skia. I imagine that whether or not there'll be some comments of the PR, the API will be the same. So that might be an idea while you wait. 🙂

[bryphe]

Wow, thanks for diving in and fixing this @JulesGuesnon - just saw your PR 👍 And nice catch on the bug.

You can always point Revery to use your PR of reason-skia.

Definitely! You should be able to add a resolution in the package.json like: "reason-skia": "link:../reason-skia", which will pick up your local version. Good way to test the new API on images.