Loading Assets

Loading and replacing assets dynamically at runtime

If you want to dynamically replace images, use image data binding.

Some Rive files may contain assets that can be embedded within the actual file binary, such as font, image, or audio files. The Rive runtimes may then load these assets when the Rive file is loaded. While this makes for easy usage of the Rive files/runtimes, there may be opportunities to load these assets in or even replace them at runtime instead of embedding them in the file binary.

There are several benefits to this approach:

• Keep the .riv files tiny without potential bloat of larger assets
• Dynamically load an asset for any reason, such as loading an image with a smaller resolution if the .riv is running on a mobile device vs. an image of a larger resolution for desktop devices
• Preload assets to have available immediately when displaying your .riv
• Use assets already bundled with your application, such as font files
• Sharing the same asset between multiple .rivs

Methods for loading assets

There are currently three different ways to load assets for your Rive files.

In the Rive editor select the desired asset from the Assets tab, and in the inspector choose the desired export option:

Embedded assets

In the Rive editor, static assets can be included in the .riv file, by choosing the “Embedded” export type. As stated in the beginning of this page, when the Rive file gets loaded, the runtime will implicitly attempt to load in the assets embedded in the .riv as well, and you don’t need to concern yourself with loading any assets manually.

Caveat: Embedded assets may bulk up the file size, especially when it comes to fonts when using Rive Text (Text Overview).

Embedded is the default option.

Image CDNs

Some image CDNs allow for on-the-fly image transformations, including resizing, cropping, and automatic format conversion based on the browser’s and device’s capabilities. These CDNs can host your Rive image assets. Note that for these CDNs, you may need to specify the accepted formats, for example, as part of the HTTP header request:

... headers: { Accept: 'image/png,image/webp,image/jpeg,*/*', } ...

Please see your CDN provider’s documentation for additional information.

Rive supports the following image formats: jpeg, png, and webp

Referenced assets

In the Rive editor, you can mark an imported asset as a “Referenced” export type, which means that when you export the .riv file, the asset will not be embedded in the file binary, and the responsibility of loading the asset will be handled by your application at runtime.

This option enables you to dynamically load in assets via a handler API when the runtime begins loading in the .riv file. This option is preferable if you have a need to dynamically load in a specific asset based on any kind of app/game logic, and especially if you want to keep the .riv file size small.

All referenced assets, including the .riv, will be bundled as a zip file when you export your animation.

Caveat: You will need to provide an asset handler API when loading in Rive which should do the work of loading in an asset yourself. See Handling Assets.

SVG assets can’t currently be loaded at runtime as referenced assets.

This is because SVGs are converted to Rive vector objects, which are always embedded into the .riv.

Handling assets

New Runtime

This section assumes that you have read through the Apple overview.

Discovering and Loading File Assets

Use File.getAssets() to discover a file’s assets, then decode and register replacements on its Worker. This replaces the legacy customLoader callback for out-of-band assets.

A global asset applies to matching assets in that file and other files loaded by the same worker, including files loaded later. Register it using asset.uniqueName. You can register assets after creating the file, and register a new asset under the same unique name to replace it.

Each File.Asset provides the following metadata:

Property	Description
name	The authored asset name stored in the file.
uniqueName	The exact name to pass to the worker’s global asset APIs.
assetID	The asset identifier stored in the file.
type	.image, .font, .audio, or .unknown(UInt16).
fileExtension	The file extension without a leading period.
cdn	Optional hosted asset metadata with baseURL and uuid.

getAssets() includes embedded and referenced assets. Use the metadata to choose which assets your app supplies.

1. Create a Worker and File

   Load the file before querying its asset metadata. Call these APIs from a main-actor async context.

   let worker = try await Worker()
   let file = try await File(
       source: .local("my_rive_file", .main),
       worker: worker
   )
   
2. Choose and Load Assets

   Iterate the file’s assets and use their metadata to locate their bytes. This example matches bundled resources using each asset’s uniqueName and fileExtension, skipping unknown asset types and resources that are not bundled.

   for asset in try await file.getAssets() {
       if case .unknown = asset.type { continue }
       guard let url = Bundle.main.url(
           forResource: asset.uniqueName,
           withExtension: asset.fileExtension
       ) else { continue }
   
       let data = try await Task.detached {
           try Data(contentsOf: url)
       }.value
   
       // Decode and register the asset here, as shown below.
   }
   
3. Register Global Assets

   Inside the loop, decode each asset with the worker and register it using asset.uniqueName. The worker applies it to files using that unique name.

   switch asset.type {
   case .image:
       let image = try await worker.decodeImage(from: data)
       worker.addGlobalImageAsset(image, name: asset.uniqueName)
   case .font:
       let font = try await worker.decodeFont(from: data)
       worker.addGlobalFontAsset(font, name: asset.uniqueName)
   case .audio:
       let audio = try await worker.decodeAudio(from: data)
       worker.addGlobalAudioAsset(audio, name: asset.uniqueName)
   case .unknown:
       break
   }
   

Complete Example

This example loads bundled resources whose filenames match each asset’s uniqueName plus its fileExtension (for example, picture-47982.jpeg). It skips assets without a matching bundled resource and leaves them unchanged.

@MainActor
func loadFileWithAssets() async throws -> File {
    let worker = try await Worker()
    let file = try await File(
        source: .local("my_rive_file", .main),
        worker: worker
    )

    for asset in try await file.getAssets() {
        if case .unknown = asset.type { continue }
        guard let url = Bundle.main.url(
            forResource: asset.uniqueName,
            withExtension: asset.fileExtension
        ) else { continue }

        let data = try await Task.detached {
            try Data(contentsOf: url)
        }.value

        switch asset.type {
        case .image:
            let image = try await worker.decodeImage(from: data)
            worker.addGlobalImageAsset(image, name: asset.uniqueName)
        case .font:
            let font = try await worker.decodeFont(from: data)
            worker.addGlobalFontAsset(font, name: asset.uniqueName)
        case .audio:
            let audio = try await worker.decodeAudio(from: data)
            worker.addGlobalAudioAsset(audio, name: asset.uniqueName)
        case .unknown:
            break
        }
    }

    return file
}

Create your Rive and view from the returned file. You can also register replacements after displaying a file. Using the same unique name updates matching assets across files on that worker; use separate workers when those files need different replacements.

Loading Hosted Assets

The new runtime does not automatically fetch hosted assets. For an asset with cdn metadata, fetch its bytes from baseURL with uuid appended as a path component, then decode and register it using the same global asset APIs.

For example, inside an asset loop, load hosted images with:

guard asset.type == .image,
      let cdn = asset.cdn,
      let baseURL = URL(string: cdn.baseURL)
else { continue }

let url = baseURL.appendingPathComponent(cdn.uuid)
let (data, response) = try await URLSession.shared.data(from: url)
guard let response = response as? HTTPURLResponse,
      (200..<300).contains(response.statusCode)
else { throw URLError(.badServerResponse) }

let image = try await worker.decodeImage(from: data)
worker.addGlobalImageAsset(image, name: asset.uniqueName)

Managing Global Assets

The worker retains registered assets, so you do not need to keep a separate strong reference while they are registered. To remove a registration, use the corresponding API with the same unique name:

worker.removeGlobalImageAsset(name: imageAsset.uniqueName)
worker.removeGlobalFontAsset(fontAsset.uniqueName)
worker.removeGlobalAudioAsset(name: audioAsset.uniqueName)

Legacy Runtime

Examples

• (SwiftUI) Swap out images and fonts
• (UIKit) Swap and cache images and fonts

Using the Asset Handler API

When instantiating a RiveViewModel (or RiveFile directly), add a customLoader callback property to the list of parameters. This callback will be called for every asset the runtime detects from the .riv file on load, and the callback will be responsible for either handling the load of an asset at runtime or passing on the responsibility and giving the runtime a chance to load it otherwise.

An instance where you may want to handle loading an asset is if an asset in the file is marked as Referenced, and you need to provide an actual asset to render for the graphic, as Rive does not embed it in the .riv and thus cannot load it.

An instance where you may want to give the runtime a chance to load the asset is if the asset in the file is marked as Hosted, and want to pass the responsibility of loading it to the runtime (which will call into a Rive CDN to do so).

RiveViewModel(fileName: "simple_assets", loadCdn: false, customLoader: { (asset: RiveFileAsset, data: Data, factory: RiveFactory) -> Bool in
    // A simple check for a Rive file with one asset
    if (asset is RiveImageAsset){
        // picture-47982.jpeg can be exported with the .riv file from the Rive editor.
        // It is then included in the main bundle resources of the project
        guard let url = (.main as Bundle).url(forResource: "picture-47982", withExtension: "jpeg") else {
            fatalError("Failed to locate 'picture-47982' in bundle.")
        }
        guard let data = try? Data(contentsOf: url) else {
            fatalError("Failed to load \(url) from bundle.")
        }
        (asset as! RiveImageAsset).renderImage(
            factory.decodeImage(data)
        )
        return true;
    }
    return false;
}).view()

Your provided callback will be passed an asset, data, and a factory.

• asset - Reference to a RiveFileAsset object. You’ll use this reference to set a new Rive-specific asset for dynamically loaded content. If you wish to dynamically swap a given image/font over the lifetime of your view, you may want to cache this object. You can grab a number of properties from this object, such as:

• name() - Name of the asset without the unique file identifier appended, (i.e. picture.webp instead of picture-47982.webp)

• uniqueFilename() - Name of the asset with the unique file identifier, (i.e. picture-47982.webp instead of picture.webp)

• fileExtension() - Name of the file extension (i.e. "png")

• cdnBaseUrl() - Name of the base URL for the CDN

• cdnUuid() - Identifier for the resource in the Rive CDN. Useful to see if this has length so you can see if the asset is marked for grabbing from a Rive CDN (in which case, you can let the Rive runtime retrieve the asset, rather than your app logic)

• data - Array of bytes for the asset. This is useful to determine if the asset is already embedded in the Rive file (aka, not marked as “referenced” in the editor)

• factory - Utility with methods to transform an asset’s bytes into a RiveRenderImage ,RiveFont, or RiveAudio which the asset object uses to render via .renderImage(your-rive-render-image) , .font(your-rive-font) , or .audio(your-rive-audio) . These assets are created by calling factory.decodeImage(data), factory.decodeFont(data), or factory.decodeAudio(data)

Important: Note that the return value of the callback is a boolean, which is where you need to return:

• true if you intend on handling and loading in an asset yourself, or
• false if you do not want to handle asset loading for that given asset yourself, and attempt to have the runtime try to load the asset.

Example Usage

import SwiftUI
import RiveRuntime

struct SimpleAssetReplacement: View {
    @StateObject private var riveInstance = RiveViewModel(fileName: "simple_assets", autoPlay: false, loadCdn: false, customLoader: { (asset: RiveFileAsset, data: Data, factory: RiveFactory) -> Bool in
        if (asset is RiveImageAsset) {
            guard let url = (.main as Bundle).url(forResource: "picture-47982", withExtension: "jpeg") else {
                fatalError("Failed to locate 'picture-47982' in bundle.")
            }
            guard let data = try? Data(contentsOf: url) else {
                fatalError("Failed to load \(url) from bundle.")
            }
            (asset as! RiveImageAsset).renderImage(
                factory.decodeImage(data)
            )
            return true;
        } else if (asset is RiveFontAsset) {
            guard let url = (.main as Bundle).url(forResource: "Inter-45562", withExtension: "ttf") else {
                fatalError("Failed to locate 'Inter-45562' in bundle.")
            }
            guard let data = try? Data(contentsOf: url) else {
                fatalError("Failed to load \(url) from bundle.")
            }
            (asset as! RiveFontAsset).font(
                factory.decodeFont(data)
            )
            return true;
        }
        return false;
    })

    var body: some View {
        riveInstance.view()
    }
}

Fonts

When using a custom loader, referenced fonts can be loaded one of two ways: with raw data (from a file, as seen above), or with a UIFont / NSFont.
When using UIFont / NSFont, size, weight, and width of the supplied font is ignored. The font will be used as defined in the text run, rather than being overridden by the supplied font’s styling.

import SwiftUI
import RiveRuntime

struct SimpleFontReplacement: View {
    @StateObject private var riveInstance = RiveViewModel(fileName: "simple_assets", autoPlay: false, loadCdn: false, customLoader: { (asset: RiveFileAsset, data: Data, factory: RiveFactory) -> Bool in
        if (asset is RiveFontAsset) {
            (asset as! RiveFontAsset).font(
                factory.decodeFont(UIFont.systemFont(ofSize: 12))
            )
            return true;
        }
        return false;
    })

    var body: some View {
        riveInstance.view()
    }
}

Images

When loading assets for referenced images, you may need to scale local assets to the size of an image asset as defined in your Rive file. When using a custom loader, you can access the size of the referenced image via the size property of a RiveImageAsset.

import SwiftUI
import RiveRuntime

struct SimpleImageSizeReplacement: View {
    @StateObject private var riveInstance = RiveViewModel(fileName: "simple_assets", autoPlay: false, loadCdn: false, customLoader: { (asset: RiveFileAsset, data: Data, factory: RiveFactory) -> Bool in
        guard let imageAsset = asset as? RiveImageAsset else { return false }
            let requestedSize = imageAsset.size
            let image = UIImage(...)
            let resizedImage = resize(image, to: requestedSize)
            guard let pngData = resizedImage.pngData() else { return false }
            imageAsset.renderImage(
                factory.decodeImage(pngData)
            )
            return true
        }
        return false;
    }

    var body: some View {
        riveInstance.view()
    }

Additional resources