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Image and in-app icons manipulations

What is covered

In this tutorial we will show you how to work with images using Compose for Desktop.

Loading images from resources

Using images from application resources is very simple. Suppose we have a PNG image that is placed in the resources directory in our project. For this tutorial we will use the image sample:

import androidx.compose.foundation.Image
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.ui.ExperimentalComposeUiApi
import androidx.compose.ui.Modifier
import androidx.compose.ui.res.painterResource
import androidx.compose.ui.window.singleWindowApplication

@OptIn(ExperimentalComposeUiApi::class)
fun main() = singleWindowApplication {
    Image(
        painter = painterResource("sample.png"), // ImageBitmap
        contentDescription = "Sample",
        modifier = Modifier.fillMaxSize()
    )
}

painterResource supports raster (BMP, GIF, HEIF, ICO, JPEG, PNG, WBMP, WebP) and vector formats (SVG, XML vector drawable).

Loading images from device storage asynchronously

To load an image stored in the device memory you can use loadImageBitmap, loadSvgPainter or loadXmlImageVector. The example below shows how to use them to load an image asynchronously.

import androidx.compose.foundation.Image
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.width
import androidx.compose.runtime.Composable
import androidx.compose.runtime.getValue
import androidx.compose.runtime.produceState
import androidx.compose.runtime.remember
import androidx.compose.ui.ExperimentalComposeUiApi
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.ImageBitmap
import androidx.compose.ui.graphics.painter.BitmapPainter
import androidx.compose.ui.graphics.painter.Painter
import androidx.compose.ui.graphics.vector.ImageVector
import androidx.compose.ui.graphics.vector.rememberVectorPainter
import androidx.compose.ui.layout.ContentScale
import androidx.compose.ui.platform.LocalDensity
import androidx.compose.ui.res.loadImageBitmap
import androidx.compose.ui.res.loadSvgPainter
import androidx.compose.ui.res.loadXmlImageVector
import androidx.compose.ui.unit.Density
import androidx.compose.ui.unit.dp
import androidx.compose.ui.window.singleWindowApplication
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.withContext
import org.xml.sax.InputSource
import java.io.File
import java.io.IOException

@OptIn(ExperimentalComposeUiApi::class)
fun main() = singleWindowApplication {
    val density = LocalDensity.current
    Column {
        AsyncImage(
            load = { loadImageBitmap(File("sample.png")) },
            painterFor = { remember { BitmapPainter(it) } },
            contentDescription = "Sample",
            modifier = Modifier.width(200.dp)
        )
        AsyncImage(
            load = { loadSvgPainter(File("idea-logo.svg"), density) },
            painterFor = { it },
            contentDescription = "Idea logo",
            contentScale = ContentScale.FillWidth,
            modifier = Modifier.width(200.dp)
        )
        AsyncImage(
            load = { loadXmlImageVector(File("compose-logo.xml"), density) },
            painterFor = { rememberVectorPainter(it) },
            contentDescription = "Compose logo",
            contentScale = ContentScale.FillWidth,
            modifier = Modifier.width(200.dp)
        )
    }
}

@Composable
fun <T> AsyncImage(
    load: suspend () -> T,
    painterFor: @Composable (T) -> Painter,
    contentDescription: String,
    modifier: Modifier = Modifier,
    contentScale: ContentScale = ContentScale.Fit,
) {
    val image: T? by produceState<T?>(null) {
        value = withContext(Dispatchers.IO) {
            try {
                load()
            } catch (e: IOException) {
                e.printStackTrace()
                null
            }
        }
    }

    if (image != null) {
        Image(
            painter = painterFor(image!!),
            contentDescription = contentDescription,
            contentScale = contentScale,
            modifier = modifier
        )
    }
}

fun loadImageBitmap(file: File): ImageBitmap =
    file.inputStream().buffered().use(::loadImageBitmap)

fun loadSvgPainter(file: File, density: Density): Painter =
    file.inputStream().buffered().use { loadSvgPainter(it, density) }

fun loadXmlImageVector(file: File, density: Density): ImageVector =
    file.inputStream().buffered().use { loadXmlImageVector(InputSource(it), density) }

PNG

SVG

XML vector drawable

Drawing raw image data using native canvas

You may want to draw raw image data, in which case you can use Canvas and drawIntoCanvas.

import androidx.compose.foundation.Canvas
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.runtime.remember
import androidx.compose.ui.ExperimentalComposeUiApi
import androidx.compose.ui.Modifier
import androidx.compose.ui.geometry.Offset
import androidx.compose.ui.graphics.ImageBitmap
import androidx.compose.ui.graphics.Paint
import androidx.compose.ui.graphics.asImageBitmap
import androidx.compose.ui.graphics.drawscope.drawIntoCanvas
import androidx.compose.ui.res.loadImageBitmap
import androidx.compose.ui.res.useResource
import androidx.compose.ui.window.singleWindowApplication
import org.jetbrains.skija.Bitmap
import org.jetbrains.skija.ColorAlphaType
import org.jetbrains.skija.ImageInfo

private val sample = useResource("sample.png", ::loadImageBitmap)

@OptIn(ExperimentalComposeUiApi::class)
fun main() = singleWindowApplication {
    val bitmap = remember { bitmapFromByteArray(sample.getBytes(), sample.width, sample.height) }
    Canvas(
        modifier = Modifier.fillMaxSize()
    ) {
        drawIntoCanvas { canvas ->
            canvas.drawImage(bitmap, Offset.Zero, Paint())
        }
    }
}

fun bitmapFromByteArray(pixels: ByteArray, width: Int, height: Int): ImageBitmap {
    val bitmap = Bitmap()
    bitmap.allocPixels(ImageInfo.makeS32(width, height, ColorAlphaType.PREMUL))
    bitmap.installPixels(bitmap.imageInfo, pixels, (width * 4).toLong())
    return bitmap.asImageBitmap()
}

// creating byte array from BufferedImage
private fun ImageBitmap.getBytes(): ByteArray {
    val buffer = IntArray(width * height)
    readPixels(buffer)

    val pixels = ByteArray(width * height * 4)

    var index = 0
    for (y in 0 until height) {
        for (x in 0 until width) {
            val pixel = buffer[y * width + x]
            pixels[index++] = ((pixel and 0xFF)).toByte() // Blue component
            pixels[index++] = (((pixel shr 8) and 0xFF)).toByte() // Green component
            pixels[index++] = (((pixel shr 16) and 0xFF)).toByte() // Red component
            pixels[index++] = (((pixel shr 24) and 0xFF)).toByte() // Alpha component
        }
    }

    return pixels
}

Setting the application window icon

You can set the icon for the window via parameter in the Window function.

Note that to change the icon on the taskbar on some OS (macOs), you should change icon in build.gradle

import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.ui.Modifier
import androidx.compose.ui.draw.paint
import androidx.compose.ui.res.painterResource
import androidx.compose.ui.window.Window
import androidx.compose.ui.window.application

fun main() = application {
    val icon = painterResource("sample.png")
    Window(
        onCloseRequest = ::exitApplication,
        icon = icon
    ) {
        Box(Modifier.paint(icon).fillMaxSize())
    }
}

Setting the application tray icon

You can create a tray icon for your application:

import androidx.compose.foundation.Image
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.ui.Modifier
import androidx.compose.ui.res.painterResource
import androidx.compose.ui.window.Tray
import androidx.compose.ui.window.Window
import androidx.compose.ui.window.application

fun main() = application {
    val icon = painterResource("sample.png")

    Tray(
        icon = icon,
        menu = {
            Item("Quit App", onClick = ::exitApplication)
        }
    )

    Window(onCloseRequest = ::exitApplication, icon = icon) {
        Image(
            painter = icon,
            contentDescription = "Icon",
            modifier = Modifier.fillMaxSize()
        )
    }
}

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