Standalone KMM Images

Image by Dall-E: “Factory which produces lots of the same products. Dark.”

Context

https://jamiecraane.dev/2021/07/27/resource_images_kmm/ describes how to use the kmm-images plugin to share images between a Kotlin Multiplatform Mobile (short KMM) Android and iOS app. You can also use kmm-images in a standalone Android app. This post describes the advantages of doing this.

Benefits of using kmm-images in an Android app

Kmm-images unifies image handling in a KMM iOS and Android app. Using kmm-images in a standalone Android app has the following advantages:

automatic conversion of SVG to Android vector drawables
automatic conversion of PNG and JPG to all required densities
support for PDF image format
ready for Kotlin Multiplatform

SVG conversion

To use an SVG in Android it must be converted to a vector drawable. To convert an SVG to a vector drawable you can:

Click on New -> Vector Asset and select the SVG to convert.
Use the resource manager to convert multiple SVG files at once.
Use an online tool to convert SVG files to vector drawables.
Use a command line tool to convert SVG files to vector drawables.

kmm-images automates this process. All SVG images present in the images folder managed by kmm-images are converted to vector drawables. After the conversion the images are placed in the drawable resource folder. kmm-images uses the Android Vector Drawable tool to do the conversion.

PNG/JPG conversion

To create multiple versions for different densities of a PNG or JPG you can:

Ask the designer to supply the image in multiple densities.
Export the image in multiple densities from the design tool of choice.
Use a tool to convert the image to multiple densities.

kmm-images supports automatic creation of all required densities for a PNG or JPG. The only requirement is to provide the images in the xxxhdpi density. kmm-images convers the images for both Android and iOS.

Support of PDF image format

To use a PDF image in Android you must convert it to a supported format. kmm-images does this conversion automatically. A PDF images is converted to an SVG. The SVG is then converted to a vector drawable for use in Android.

Ready for Kotlin Multiplatform

When you integrate kmm-images into an Android project means no more refactoring when the Android app is migrated to Kotlin Multiplatform Mobile.

Integrating kmm-images in an Android app

To integrate kmm-images in an Android app, add the following to the Android app build.gradle.kts file:

Add the following to the plugins section:

 id("dev.jamiecraane.plugins.kmmimages") version "1.0.0-alpha11"

Add the following section to configure kmm-images:

kmmImagesConfig {
    imageFolder.set(project.projectDir.resolve("images"))
    sharedModuleFolder.set(project.projectDir)
    androidResFolder.set(project.projectDir.resolve("src/main/generated-res"))
    packageName.set("<YOUR_PACKAGE_NAME>")
    defaultLanguage.set("en")
    usePdf2SvgTool.set(true) // optional parameter
}

Hook the generateImages task to the preBuild task:

var generateImages = tasks["generateImages"]
tasks["preBuild"].dependsOn(generateImages)

Add the generated-res to the sourceSets in the android configuration section:

sourceSets {
    getByName("main") {
        res.srcDirs("src/main/generated-res")
    }
}