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CLOUDY KOTLIN MULTIPLATFORM BLUR AND LIQUID GLASS EFFECT LIBRARY FOR COMPOSE.

Cloudy: Kotlin Multiplatform Blur and Liquid Glass Effect Library for Compose

We are dedicated to exploring and providing resources that elevate the development of modern, visually stunning applications. In the realm of Kotlin Multiplatform (KMP) and Jetpack Compose, achieving sophisticated visual effects such as background blurring and the popular “frosted glass” or “liquid glass” aesthetic has historically been a complex challenge, often requiring platform-specific implementations. Today, we delve into a comprehensive analysis of Cloudy, a powerful open-source library designed to bridge this gap. Cloudy allows developers to implement high-performance blur and liquid glass effects seamlessly across Android, iOS, and Desktop platforms using a unified Kotlin codebase.

This article serves as an in-depth technical guide and reference for developers looking to integrate professional-grade visual effects into their Compose Multiplatform projects. We will explore the architecture, implementation details, and optimization strategies necessary to leverage Cloudy effectively.

Understanding the Visual Aesthetic: Blur and Liquid Glass in Modern UI

The modern user interface landscape is heavily defined by depth, hierarchy, and immersion. The “liquid glass” effect—often referred to as glassmorphism—is characterized by transparency, background blurring, and subtle border lighting. This design language provides a sense of physical depth, making UI elements appear to float above the underlying content.

The Challenge of Cross-Platform Rendering

Implementing these effects natively requires deep interaction with the operating system’s rendering pipeline. On Android, this involves RenderEffect and BlurCanvas. On iOS, it utilizes UIVisualEffectView with UIBlurEffect. For Desktop (JVM), it may rely on Java’s AWT or specific hardware acceleration APIs. Without a unified abstraction, maintaining consistency across these platforms is a significant burden for KMP developers.

The Role of Compose Multiplatform

Jetpack Compose Multiplatform has revolutionized UI development by allowing a single declarative UI codebase to target multiple platforms. However, Compose’s built-in effects are currently limited. While basic transparency is trivial, high-fidelity hardware-accelerated blurring is not natively supported in the core Compose library for all targets. This is where a specialized library like Cloudy becomes indispensable. It abstracts the native complexity, providing a pure Kotlin API that integrates directly into the Compose modifier chain.

Deep Dive into the Cloudy Architecture

Cloudy is architected to be lightweight, efficient, and extensible. It operates by intercepting the drawing operations of a Composable, capturing the content behind a specific area, applying the blur algorithm, and rendering the result on top. This process must happen per-frame during animations to maintain the fluidity expected in modern mobile applications.

Core Principles of Cloudy

The library is built around a few central concepts:

  1. Platform Abstraction: Cloudy uses the expect and actual mechanism of Kotlin Multiplatform to define a common interface for blur operations while delegating to optimized native implementations.
  2. Modifier Integration: The primary usage pattern is through a Compose Modifier. This ensures that the blur effect behaves like any other layout attribute, respecting bounds, padding, and composition changes.
  3. Performance First: Blur operations are computationally expensive. Cloudy employs optimization techniques such as downsampling (blurring a lower-resolution version of the image) and limiting redraws to dirty regions to maintain high frame rates.

Platform-Specific Implementation Details

Android Implementation

On Android, Cloudy leverages the RenderEffect API (available on Android 12+) and BlurMaskFilter for older versions. It utilizes the AndroidGraphicsLayer to capture the composable’s content. The library effectively creates a snapshot of the underlying pixels, applies a Gaussian blur, and draws it onto the DrawScope. For devices running Android 13+, it takes advantage of hardware-accelerated shaders to ensure minimal CPU overhead.

iOS Implementation

For iOS, Cloudy bridges with UIKit to utilize UIVisualEffectView. This is the most performant way to achieve blurring on Apple devices, as it is handled directly by the GPU. The library wraps this native view within a Compose UIKitView, ensuring the blur updates reactively as the underlying content changes. This hybrid approach ensures that the effect feels native to iOS users while remaining part of the Kotlin shared logic.

Desktop Implementation

Targeting Desktop (JVM), Cloudy typically relies on Java’s BufferedImage operations or hardware-accelerated pipelines provided by libraries like Skia (via Skiko). The implementation focuses on balancing quality with CPU usage, often utilizing multi-threading to apply blur filters without blocking the UI thread.

Integrating Cloudy into Your Compose Multiplatform Project

Integrating Cloudy is straightforward, but maximizing its potential requires understanding the nuances of the API. We will guide you through the setup and usage patterns.

Dependency Setup

To begin, you must add the Cloudy dependency to your shared module’s build.gradle.kts file. It is crucial to use the latest stable version to ensure compatibility with the newest Kotlin and Compose Multiplatform releases.

// In your shared module build.gradle.kts
dependencies {
    implementation("com.github.skydoves:cloudy:0.x.x") // Check for the latest version
}

Basic Usage: The blur Modifier

The simplest way to apply a blur effect is using the provided modifier. This modifier takes a radius value, which determines the intensity of the blur.

@Composable
fun BlurryCard() {
    Box(
        modifier = Modifier
            .fillMaxSize()
            .background(Color.Blue)
    ) {
        // This content will be blurred
        Box(
            modifier = Modifier
                .size(200.dp)
                .blur(radius = 10.dp) // Applies the blur effect
                .background(Color.White.copy(alpha = 0.5f))
        ) {
            Text("Blurred Background")
        }
    }
}

In this example, the blur modifier captures the blue background behind the white box and applies a Gaussian blur with a radius of 10 pixels (scaled to density). This creates an immediate frosted glass effect.

Advanced Usage: The cloudy Modifier for Dynamic Effects

For scenarios requiring more control—such as animating the blur radius or applying the effect to a specific child composables—the cloudy modifier is recommended. This modifier returns a state that can be observed and manipulated.

@Composable
fun DynamicGlassEffect() {
    var blurRadius by remember { mutableStateOf(0.dp) }

    // Animate the blur radius
    val animatedRadius by animateDpAsState(
        targetValue = blurRadius,
        animationSpec = tween(durationMillis = 500)
    )

    Column {
        // Content to be blurred
        Image(
            painter = painterResource("background_image.png"),
            contentDescription = null,
            modifier = Modifier.fillMaxWidth()
        )

        // Overlay with blur
        Box(
            modifier = Modifier
                .fillMaxSize()
                .cloudy(radius = animatedRadius)
                .clickable { blurRadius = if (blurRadius == 0.dp) 20.dp else 0.dp }
        ) {
            Text("Tap to toggle blur")
        }
    }
}

This pattern allows for interactive UI elements where the background blurs in response to user actions, such as opening a modal or focusing on a text field.

Optimizing Performance for High-Frame-Rate Animations

Blur effects are notoriously performance-intensive. Without careful optimization, they can cause frame drops, especially on mid-range devices. We recommend the following strategies when using Cloudy in production applications.

Downsampling and Resolution Management

One of the most effective ways to improve blur performance is to reduce the resolution of the input texture before applying the blur algorithm. Cloudy handles this internally to an extent, but developers can assist by constraining the layout size. Avoid applying full-screen blurs to 4K resolution textures if the visual area is small.

Caching Strategies

Static backgrounds do not need to be re-blurred every frame. Cloudy implements caching mechanisms for the underlying bitmap data. However, when using animations, ensure that the animation triggers are optimized. Use remember to cache the blurred bitmap for static content and only invalidate the cache when the underlying content changes.

Limiting Blur Radius

While high blur radii look appealing, they require exponentially more processing power. A radius of 20dp is significantly more expensive than 10dp. We recommend keeping blur radii between 4dp and 16dp for most UI elements to maintain 60fps (or 120fps on high-refresh-rate screens).

Handling Nested Blurs

Stacking multiple blurred layers (blurring a blurred background) can lead to severe performance degradation and visual artifacts. It is best practice to avoid nesting Cloudy modifiers. If a design requires depth, apply a single blur layer to the background and keep foreground elements opaque or translucent without blur.

Design Patterns for Glassmorphism with Cloudy

To create professional designs using Cloudy, we must adhere to specific design patterns that ensure readability and aesthetic consistency.

Contrast and Readability

Glassmorphism relies on transparency, which can make text difficult to read if the background is too busy. To mitigate this:

  1. Saturation: Ensure the blurred background has sufficient saturation to distinguish it from the foreground.
  2. Text Color: Use high-contrast text colors. White text on a dark, blurred background usually works well.
  3. Borders: Adding a subtle, 1px white border with low opacity helps separate the glass layer from the background.

Layering and Depth

The liquid glass effect is most convincing when multiple layers are involved.

This z-axis separation creates the illusion of depth. We recommend using Modifier.zIndex in Compose to manage stacking order explicitly.

Comparing Cloudy with Alternative Solutions

Before Cloudy, developers often resorted to writing platform-specific code or using older libraries that did not support KMP. Here is how Cloudy stands out:

Handling Lifecycle and Memory Management

A critical aspect of any graphics library is how it manages memory, particularly on mobile devices where RAM is limited.

Bitmap Recycling

Cloudy actively manages the lifecycle of bitmaps used for capturing screen content. When a Composable leaves the composition or the blur effect is disabled, the underlying resources are released to prevent memory leaks. This is particularly important for lists (LazyColumn/LazyRow) where items are constantly composed and decomposed.

Configuration Changes

On Android, configuration changes (like screen rotation) can destroy and recreate the Activity. Cloudy integrates with the Compose lifecycle to ensure that blur resources are reinitialized correctly without retaining stale references to destroyed contexts.

Customization and Theming

Cloudy is designed to be flexible. While the default Gaussian blur is standard, the library allows for customization of the visual output.

Modifying Blur Shaders

For advanced use cases, developers can inject custom shaders or bitmap processors. This allows for effects like variable blurring (where the blur intensity changes based on the pixel’s position) or combining blur with color filters (e.g., a sepia-tone glass effect).

Integration with Material Design 3

Cloudy fits naturally into Material Design 3 (MD3) workflows. The surface container color in MD3 often utilizes transparency. By applying Cloudy to the background of a Surface composable, you can achieve a “vibrant” surface that dynamically adapts to the wallpaper behind it, a feature prominent in modern Android (Material You).

Troubleshooting Common Issues

While Cloudy is robust, complex UIs can sometimes present challenges.

Flickering During Animation

If you notice flickering while animating the blur radius, it is likely due to the input texture being re-captured faster than it can be processed. To fix this, consider:

Platform Inconsistencies

Blur algorithms differ slightly between platforms (CoreGraphics on iOS vs. Skia on Android/Desktop). This may result in subtle visual differences. We recommend testing designs on all target platforms and adjusting radius values slightly per platform if pixel-perfect consistency is required.

Conclusion: The Future of KMP UI with Cloudy

Cloudy represents a significant step forward in the maturity of the Kotlin Multiplatform ecosystem. By providing a performant, declarative API for complex visual effects, it empowers developers to build beautiful, immersive applications without sacrificing the productivity gains of shared code. Whether you are building a finance app, a media player, or a social network, the liquid glass effect adds a layer of sophistication that users appreciate. By following the implementation strategies outlined in this guide—optimizing for performance, managing memory, and adhering to design principles—you can leverage Cloudy to create stunning, high-performance interfaces that stand out in the market.

As the KMP ecosystem evolves, we anticipate libraries like Cloudy will become foundational components of the standard UI toolkit, making cross-platform visual fidelity not just possible, but effortless.

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