# Design: Heavy Blur Background via Coil BlurTransformation

**Date:** 2026-03-18  
**Status:** Approved

## Problem

The player screen's blurred album art background uses the Cloudy library at its maximum radius of 25. This is insufficient — album art with text remains legible and fine details are still visible, breaking the intended "washed out background" aesthetic.

## Solution

Replace Cloudy with a self-contained Stackblur `BlurTransformation` applied via Coil's image loading pipeline. Blur is baked into the decoded bitmap on a background thread, producing a heavily smeared result with no legible text or sharp edges.

## Changes

### 1. Add `BlurTransformation.kt`

Create `app/src/main/java/xyz/cottongin/radio247/ui/util/BlurTransformation.kt`.

A ~130-line pure Kotlin + Android bitmap Stackblur implementation (no new library dependency). Accepts:
- `radius: Int` — blur radius (25 is already very aggressive at low scale)
- `scale: Float` — downsample factor applied before blurring (0.1f = 10% of original size)

### 2. Update `BlurredBackground` in `NowPlayingScreen.kt`

- Remove `.cloudy(radius = 25)` modifier
- Remove `size(10, 10)` from the `ImageRequest` (scale parameter in the transformation handles downsampling)
- Add `transformations(BlurTransformation(radius = 25, scale = 0.1f))` to the `ImageRequest`
- Remove Cloudy import

### 3. Remove Cloudy dependency

- Remove `implementation(libs.cloudy)` from `app/build.gradle.kts`
- Remove `cloudy` version and library entries from `gradle/libs.versions.toml`

## Parameters

| Parameter | Value | Rationale |
|-----------|-------|-----------|
| `radius`  | 25    | Maximum effective Stackblur radius before diminishing returns |
| `scale`   | 0.1f  | Downsamples to 10% before blurring, destroying fine detail and text |

## Trade-offs

- **No new dependency** — implementation is inlined as a project file
- **All API levels** — pure bitmap manipulation, no RenderEffect/RenderScript
- **Background thread** — blur computed by Coil pipeline, zero per-frame GPU cost
- **Not animatable** — blur is baked at load time; cannot be animated at runtime (acceptable for this use case)