Set application icon

[KiraResari]

I am now trying to set an application icon to my iced application. I've tried this as follows:

pub fn main() -> iced::Result {
    let mut settings = Settings::default();
    settings.window.icon =  Icon::from_rgba(
        include_bytes!(
            "../resources/images/Kanji Tree R Icon.ico"
        ).to_vec(),
        512,
        512
    ).ok();
    kanji_tree::KanjiTreeApp::run(settings)
}

However, in that case, from_rgba returns the following error:

DimensionsMismatch
* width: 512
* height: 512
* pixel_count: 34359

I've also tried this with icons of different sizes and file types, and sometimes it returns an error like the following instead (for a 32x32 .ico):

InvalidData
* byte_count: 4286
* [raw]
** variant0:
*** byte_count: 4286
** variant1:
*** width: 385
*** height: 4286
*** pixel_count: 1653562408960

I haven't been able to find a way to get this to work. Can someone please help me with that?

[BlackHoleFox]

You need to decode the image data into raw bytes first.

Here's an example which uses the image crate to do that. Replace the constants with the properties/location/etc of your actual icon.

static ICON: &[u8] = include_bytes!("../icon.png");
const ICON_HEIGHT: u32 = 64;
const ICON_WIDTH: u32 = 64;

fn main() {
    let image = image::load_from_memory(ICON).unwrap();
    let icon = iced::window::Icon::from_rgba(image.as_bytes().to_vec(), ICON_HEIGHT, ICON_WIDTH).unwrap();
    
    let settings = iced::settings::Settings {
        window: iced::window::Settings {
            icon: Some(icon), 
            ..Default::default()
        },
        ..Default::default()
    };

    YourApplication::run(settings)
    ...
}

[BlackHoleFox]

The same thing should work. You just need to enable the ico feature of image.

If you want to make the icon show up as the executable's icon itself though (assuming this is Windows), you'll want to use the winres crate.

[KiraResari]

I already managed to make the icon show up in the compiled exe.

However, using the .ico for the app icon isn't working yet.

So, I did enable the ico feature of image like this:

image = {version = "0.24.1", features = ["ico"] }

...and then I tried calling it like this:

static ICON: &[u8]
     = include_bytes!("../resources/images/Kanji Tree R Icon.ico");
const ICON_HEIGHT: u32 = 512;
const ICON_WIDTH: u32 = 512;

pub fn main() -> iced::Result {
    let settings = build_settings();
    kanji_tree::KanjiTreeApp::run(settings)
}

fn build_settings() -> Settings<()> {
    let image
        = image::load_from_memory(ICON).unwrap();
    let icon = Icon::from_rgba(
        image.as_bytes().to_vec(),
        ICON_HEIGHT,
        ICON_WIDTH
    ).unwrap();
    Settings {
        window: iced::window::Settings {
            icon: Some(icon), 
            ..Default::default()
        },
        ..Default::default()
    }
}

However, then I get this error:

thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Decoding(DecodingError { format: Exact(Ico), underlying: Some(ImageEntryDimensionMismatch { format: Png, entry: (256, 256), image: (512, 512) }) })', src\main.rs:17:41

I checked, and the ico dimensions are 512x512. However, I notice that the format: Png is wrong here, and I tried reading the documentation of image, but wasn't able to figure out what I need to change to make it use .ico instead. Can you maybe elaborate?

Also, if I use the same code and specify a .png instead of an .ico (I have both versions lying side by side in my resources folder) it works just fine.

[BlackHoleFox]

Seems like the image data embedded in the .ico file is too large? Wikipedia says the format supports up to 256x256 and the image source code also seems to agree. Meanwhile, the actual png inside is 512x512 according to that error from here.

[KiraResari]

Ah, looks like that was it! Thanks for pointing that out! It now changed it to 256x256, and it works just fine.

The interesting thing here is, however, that the build.rs was able to handle the 512x512 ico file just fine. I suppose they use different approaches for handling ico files.

[BlackHoleFox]

I'd not be shocked at all if rc.exe (the thing winres invokes) just silently shrunk larger icons for more broad compatibility.

[dassio]

i am using iced 0.4.2 on windows 10 with the accepted answer code, but still get the DimensionsMismatch error, anyone else experiencing this ?