Minimal example of using screen/multiply wanted

[ProgrammingLife]

Could you please provide me with a little example of using screen/multiply blend modes to get new modified pixel?
My attempt is:

use palette::{ Hsl, IntoColor, Srgb };
let mut img1 = image::open( "data/img1.png" ).unwrap();
let mut img2 = image::open( "data/img2.png" ).unwrap();
let c1 = img1.get_pixel( 10, 10 );
let c2 = img2.get_pixel( 10, 10 );
let new_pixel: Hsl = Srgb::from( c2.0 ).into_format().into_color(); // <-- Here is the problem
// img1.put_pixel( 10, 10, new_pixel.into_format().into() );

I get following error message near "Srgb::from":

[rustc E0277] [E] the trait bound `palette::rgb::Rgb<palette::encoding::Srgb, _>: std::convert::From<[u8; 4]>` is not satisfied
the trait `std::convert::From<[u8; 4]>` is not implemented for `palette::rgb::Rgb<palette::encoding::Srgb, _>`
help: the following implementations were found:
        <palette::rgb::Rgb<S, T> as std::convert::From<(T, T, T)>>
        <palette::rgb::Rgb<S, u8> as std::convert::From<palette::Packed<C>>>
        <palette::rgb::Rgb<S, u8> as std::convert::From<u32>>
        <palette::rgb::Rgb<palette::encoding::Linear<palette::encoding::Srgb>, U> as std::convert::From<palette::rgb::Rgb<palette::encoding::Srgb, T>>>
        <palette::rgb::Rgb<palette::encoding::Srgb, U> as std::convert::From<palette::rgb::Rgb<palette::encoding::Linear<palette::encoding::Srgb>, T>>>

What do I do wrong? How to fix this issue?

Env:

rust: rustc 1.57.0 (f1edd0429 2021-11-29)
os: Linux Mint 19.1
Cargo.toml:

[dependencies]
image = "0.23.14"
palette = "0.6"

[Ogeon]

Hello! Similar to your question about the hue related trait, if you are using the examples in the repo at the moment, they will be written for a future version of the library. The recommended way to convert from an array in 0.6.0 is to use the Pixel trait. After you have your Srgba color, you can follow the examples in the blend module: https://docs.rs/palette/0.6.0/palette/blend/index.html.

[ProgrammingLife]

Thanks for the reply! I don't understand how to convert it back to image::Pixel after having c-variable here:

	let a = LinSrgba::new( 0.2, 0.5, 0.1, 0.8 );
	let b = LinSrgba::new( 0.6, 0.3, 0.5, 0.1 );
	let c = a.overlay( b );

	let new_pixel: Hsl = Srgba::from( &c ).into_format().into_color();
	let new_pixel: Hsl = Srgba::from_raw( &c ).into_format().into_color();

	img1.put_pixel( 10, 10, new_pixel );
	img1.put_pixel( 10, 10, image::Rgba( Srgba::from_color( c.into_format().into_color() ) ) ); // mistmatched types

#[derive(PartialEq, Debug, palette::Pixel)]
#[repr(C)]
struct MyRGBA {
    red: u8,
    green: u8,
    blue: u8,
    alpha: u8,
}
// ...
	let a = LinSrgba::new( 0.2, 0.5, 0.1, 0.8 );
	let b = LinSrgba::new( 0.6, 0.3, 0.5, 0.1 );
	let c = a.overlay( b );

	let new_pixel: Hsl = MyRGBA::from_raw( &c ).into_format().into_color();

I have no clue how should it work...

[Ogeon]

In the lingo of the Pixel trait, "raw" color data is arrays and slices. That's what you have in your image:

use palette::{ Hsl, IntoColor, Srgb, Pixel, Blend };
let mut img1 = image::open( "data/img1.png" ).unwrap();
let mut img2 = image::open( "data/img2.png" ).unwrap();
let c1 = img1.get_pixel( 10, 10 ); // c1.0 is an array
let c2 = img2.get_pixel( 10, 10 ); // c2.0 is an array

So to work with the colors c1 and c2 with Palette color types, you first need to convert from "raw" format:

let a = Srgba::from_raw( c1.0 ).into_format().into_linear();
let b = Srgba::from_raw( c2.0 ).into_format().into_linear();

Then we can overlay them:

let new_pixel = a.overlay( b ); // new_pixel is also LinSrgba

Finally we convert it back to non-linear, then u8 and then "raw":

img1.put_pixel( 10, 10, image::Rgba( Srgba::from_color( new_pixel ).into_format().into_raw() ) );

This is completely untested, but it may give you an idea of how it's meant to work. The whole thing with "raw" and the way the Pixel trait works is a bit funky, hence why I have rewritten it completely in the upcoming version. :)

[ProgrammingLife]

use palette::{ Hsl, IntoColor, Srgb, Pixel, Blend };
let mut img1 = image::open( "data/img1.png" ).unwrap();
let c1 = img1.get_pixel( 10, 10 ); // c1.0 is an array
let a = Srgba::from_raw( c1.0 ).into_format().into_linear();

Thanks for trying me to help but it doesn't work either:

[rustc E0599] [E] no function or associated item named `from_raw` found for struct `palette::Alpha<palette::rgb::Rgb<palette::encoding::Srgb, _>, _>` in the current scope
function or associated item not found in `palette::Alpha<palette::rgb::Rgb<palette::encoding::Srgb, _>, _>`
help: items from traits can only be used if the trait is in scope

When will be the upcoming version released?

[Ogeon]

You have probably not imported the Pixel trait, using use palette::Pixel somewhere, or like in the first part of the example. "help: items from traits can only be used if the trait is in scope" is a hint of that. Traits have to be imported for their methods to be callable.

As for the next version, I don't set release dates. I have a few more traits I want to fix up first. You can always use a git URL in you dependencies if you don't intend to publish your project on crates.io, but that comes with a higher risk of breaking changes whenever you update the Palette dependency. See the cargo documentation if you want to try that: https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#specifying-dependencies-from-git-repositories