Print files and images with a simple Printer API; capture or record Composable UI into ImageBitmaps using ScreenshotState and ScreenshotArea, with adjustable refresh rate and recording Flow.
Kotlin Multiplatform Print
Multiplatform Print is a Kotlin Multiplatform library for printing files on Android, iOS, and Desktop.
It provides two packages to handle printing:
printer-coreprinter-composeYou can see the library in action by running the :demo module, but ill provide a video of all platforms running demo module, and a quick overview of the library usage below.
https://github.com/user-attachments/assets/9b67fca0-09b5-410d-945d-2a0e5e2634b3
printer-coreMain package to print stuff, the library exposes a common API:
interface Printer {
// send to printer any file, regardless of the extension.
// no error handling, ill just trust you in this one
suspend fun print(filePath: String)
// send to printer an ImageBitmap, in case you want to print a custom image
suspend fun print(imageBitmap: )
}
printer-core Usage
@Composable
fun App() {
val printer = koinInject<Printer>()
Button(
onClick = {
val filePath = "/path/to/random/file"
// print any file extension
printer.print(filePath)
val imageBitmap = ImageBitmap(100, 100)
// or just print an imageBitmap
printer.print(imageBitmap)
}
) {
Text("Send to printer!!!")
}
}
printer-composeLibrary used to take screenshots of @Composables or just record them in a set time interval.
printer-compose Usage// screenshot usage:
@Composable
fun App() {
val screenshotState = rememberScreenshotState()
Column(Modifier.fillMaxWidth(), horizontalAlignment = Alignment.CenterHorizontally) {
Button(
onClick = {
coroutineScope.launch {
// take a screenshot of the current value:
val screenshot: ImageBitmap = screenshotState.takeScreenshot()
}
}
) { Text("Print below content") }
ScreenshotArea(screenshotState) {
Text("Hello World!")
}
}
}
@Composables
interface ScreenshotState {
// time delay between each screenshot, default 20ms
val refreshRate: Duration
// graphicsLayer used to draw the content of the composable to a ImageBitmap
val graphicsLayer: GraphicsLayer
// flow that emits the ImageBitmap of the current composable
fun startRecording(): Flow<ImageBitmap>
// one-shot function that takes a screenshot of the current composable
suspend fun takeScreenshot(): ImageBitmap
}
// Composable that wraps the content to be recorded/taken a screenshot
fun ScreenshotArea(
screenshotState: ScreenshotState,
modifier: Modifier = Modifier,
content: @Composable () -> Unit,
): Unit {}
// recording screen usage:
fun App() {
var count by remember { mutableStateOf(0) }
LaunchedEffect(Unit) {
while (true) {
delay(1000)
count++
}
}
// refreshRate param is optional, if not provided the default value is 20ms
val screenshotState = rememberScreenshotState(1.seconds)
val recordedScreen by screenshotState.startRecording().collectAsState(null)
Column(Modifier.fillMaxWidth(), horizontalAlignment = Alignment.CenterHorizontally) {
recordedScreen?.let {
Image(
bitmap = it,
contentDescription = "recording"
)
}
ScreenshotArea(screenshotState) {
// when the count changes the UI, screenshotState will collect the new value
Text("Hello World. Count: $count")
}
}
}
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