Jetpack Compose: Image Composable and Efficient Loaders

In Jetpack Compose, displaying images is a fundamental part of building user interfaces. Compose provides the Image composable, a powerful tool for rendering images efficiently. However, handling image loading, caching, and transformations efficiently often requires the use of dedicated image loading libraries. This post explores how to use the Image composable along with popular image loaders in Jetpack Compose.

What is the Image Composable?

The Image composable in Jetpack Compose is used to display images. It leverages the power of Compose’s declarative UI approach, allowing you to define images easily and efficiently. The Image composable can render images from various sources, including resources, assets, and network URLs.

Why Use Image Loaders?

Image loading libraries are essential for handling various aspects of image display, such as:

• Asynchronous Loading: Loading images in the background to prevent UI freezes.
• Caching: Storing images for quick retrieval and reduced network usage.
• Transformations: Applying effects like resizing, cropping, and applying filters.
• Resource Management: Optimizing memory usage when dealing with large images.

Popular Image Loading Libraries for Jetpack Compose

• Coil: Kotlin-first, modern image loader backed by Kotlin coroutines.
• Glide: Robust image loader from Google, well-suited for Android.
• Picasso: Developed by Square, known for its simplicity and ease of use.

Using Coil with Jetpack Compose

Coil is a lightweight and modern image loading library built specifically for Kotlin. It’s easy to use and integrates seamlessly with Jetpack Compose.

Step 1: Add the Coil Dependency

Include the Coil Compose dependency in your build.gradle file:

dependencies {
    implementation("io.coil-kt:coil-compose:2.5.0")
}

Step 2: Load an Image Using Coil’s AsyncImage

Use the AsyncImage composable to load images from a URL:

import androidx.compose.foundation.layout.*
import androidx.compose.material3.CircularProgressIndicator
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.dp
import androidx.compose.ui.tooling.preview.Preview
import coil.compose.AsyncImage
import coil.compose.SubcomposeAsyncImage

@Composable
fun CoilImageExample() {
    val imageUrl = "https://via.placeholder.com/600x400"

    Column(
        modifier = Modifier
            .fillMaxSize()
            .padding(16.dp),
        verticalArrangement = Arrangement.Center,
        horizontalAlignment = Alignment.CenterHorizontally
    ) {
        SubcomposeAsyncImage(
            model = imageUrl,
            contentDescription = "Example Image",
            loading = {
                CircularProgressIndicator()
            },
            error = {
                Text("Failed to load image")
            },
            modifier = Modifier.size(300.dp)
        )
    }
}

@Preview(showBackground = true)
@Composable
fun CoilImageExamplePreview() {
    CoilImageExample()
}

Explanation:

• Import Necessary Classes: AsyncImage, CircularProgressIndicator, etc.
• Define AsyncImage: Load an image using Coil, defining a content description for accessibility.
• Customize Loading State: Display a CircularProgressIndicator while loading.
• Handle Errors: Display an error message if the image fails to load.

Using Glide with Jetpack Compose

Glide is another powerful image loading library. To use Glide in Jetpack Compose, you can leverage the rememberGlidePainter.

Step 1: Add the Glide and Glide-Compose Dependencies

Include the necessary dependencies in your build.gradle file:

dependencies {
    implementation("com.github.bumptech.glide:glide:4.16.0")
    implementation("com.github.bumptech.glide:compose:1.0.0-alpha.1")
    annotationProcessor("com.github.bumptech.glide:compiler:4.16.0")
}

Step 2: Load an Image Using Glide’s rememberGlidePainter

Here’s how to load an image using Glide in Jetpack Compose:

import androidx.compose.foundation.Image
import androidx.compose.foundation.layout.*
import androidx.compose.material3.CircularProgressIndicator
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.dp
import androidx.compose.ui.tooling.preview.Preview
import com.bumptech.glide.integration.compose.ExperimentalGlideComposeApi
import com.bumptech.glide.integration.compose.GlideImage
import com.bumptech.glide.integration.compose.placeholder

@OptIn(ExperimentalGlideComposeApi::class)
@Composable
fun GlideImageExample() {
    val imageUrl = "https://via.placeholder.com/600x400"

    Column(
        modifier = Modifier
            .fillMaxSize()
            .padding(16.dp),
        verticalArrangement = Arrangement.Center,
        horizontalAlignment = Alignment.CenterHorizontally
    ) {
        GlideImage(
            model = imageUrl,
            contentDescription = "Example Glide Image",
            loading = placeholder {
                CircularProgressIndicator()
            },
            failure = placeholder {
                Text("Failed to load image with Glide")
            },
            modifier = Modifier.size(300.dp)
        )
    }
}

@Preview(showBackground = true)
@Composable
fun GlideImageExamplePreview() {
    GlideImageExample()
}

Key parts of this code:

• Dependencies: Add Glide and Glide-Compose dependencies in your build.gradle file.
• Import Statements: Import required Glide Compose classes.
• GlideImage Composable: A simple example displaying a remote image, handling the loading and error states using Glide.

Transformations

Image loading libraries also support transformations like resizing and cropping. Here’s how you can apply transformations with Coil:

import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.layout.ContentScale
import androidx.compose.ui.tooling.preview.Preview
import androidx.compose.ui.unit.dp
import androidx.compose.foundation.layout.size
import coil.compose.AsyncImage
import coil.transform.CircleCropTransformation

@Composable
fun CoilWithTransformationsExample() {
    val imageUrl = "https://via.placeholder.com/300"

    AsyncImage(
        model = coil.request.ImageRequest.Builder(LocalContext.current)
            .data(imageUrl)
            .crossfade(true)
            .transformations(CircleCropTransformation())
            .build(),
        contentDescription = "Transformed Image",
        contentScale = ContentScale.Crop,
        modifier = Modifier.size(150.dp)
    )
}

@Preview(showBackground = true)
@Composable
fun CoilWithTransformationsExamplePreview() {
    CoilWithTransformationsExample()
}

Conclusion

Efficient image handling is crucial for creating a polished and performant Android application with Jetpack Compose. The Image composable combined with image loading libraries like Coil and Glide provides a robust and flexible solution. By leveraging these tools, you can manage image loading, caching, and transformations efficiently, ensuring a great user experience.