Pixijs Filters

Attach visual effects by assigning one filter (or an array for chaining) to `container.filters`. Built-in filters cover blur, color matrix, displacement, alpha, and noise; custom filters wrap a GLSL/WGSL fragment shader via `Filter.from(...)`.

## Quick Start

```ts
const sprite = new Sprite(await Assets.load("hero.png"));
app.stage.addChild(sprite);

const blur = new BlurFilter({ strength: 4, quality: 4 });
const colorMatrix = new ColorMatrixFilter();
colorMatrix.brightness(1.2, false);

sprite.filters = [blur, colorMatrix];

const container = new Container();
container.filters = [new BlurFilter({ strength: 2 })];
container.filterArea = new Rectangle(0, 0, 800, 600);
app.stage.addChild(container);
```

**Related skills:** `pixijs-custom-rendering` (shader internals, uniform types), `pixijs-blend-modes` (composing with filters), `pixijs-performance` (filter tuning, filterArea).

## Core Patterns

### Built-in filters

```ts
import {
  AlphaFilter,
  BlurFilter,
  ColorMatrixFilter,
  DisplacementFilter,
  NoiseFilter,
  Assets,
  Sprite,
} from "pixi.js";

// Alpha (uniform transparency without per-child layering)
const alpha = new AlphaFilter({ alpha: 0.5 });

// Blur — strength/quality are uniform; strengthX/strengthY split axes;
// kernelSize must be odd (5, 7, 9, ... 15); repeatEdgePixels avoids transparent edges
const blur = new BlurFilter({
  strength: 4,
  quality: 4,
  kernelSize: 5,
  repeatEdgePixels: false,
});

// Color matrix — brightness is one of many presets. Others: tint, hue,
// contrast, saturate, desaturate, greyscale/grayscale, blackAndWhite,
// negative, sepia, technicolor, polaroid, kodachrome, browni, vintage,
// colorTone, night, predator, lsd, reset. Direct access via
// `colorMatrix.matrix` (20-element array) and `colorMatrix.alpha` (blend
// between original and transformed).
const colorMatrix = new ColorMatrixFilter();
colorMatrix.brightness(1.5, false);
colorMatrix.contrast(0.5, true); // multiply stacks on top of existing matrix
colorMatrix.alpha = 0.7; // blend at 70% strength

// Displacement — scale is a number or PointData
const displacementTexture = await Assets.load("displacement_map.png");
const displacementSprite = new Sprite(displacementTexture);
const displacement = new DisplacementFilter({
  sprite: displacementSprite,
  scale: { x: 20, y: 10 },
});

// Noise — seed is an arbitrary number that determines the noise pattern; same seed reproduces the same pattern
const noise = new NoiseFilter({ noise: 0.5, seed: Math.random() });

sprite.filters = [blur, colorMatrix];
```

### Custom filter with Filter.from()

The simplest way to create a custom filter. Only a fragment shader is needed; PixiJS provides a default vertex shader.

```ts
import { Filter } from "pixi.js";

const filter = Filter.from({
  gl: {
    fragment: `
            in vec2 vTextureCoord;
            out vec4 finalColor;
            uniform sampler2D uTexture;
            uniform float uTime;

            void main() {
                vec2 uv = vTextureCoord;
                uv.x += sin(uv.y * 10.0 + uTime) * 0.02;
                finalColor = texture(uTexture, uv);
            }
        `,
  },
  resources: {
    timeUniforms: {
      uTime: { value: 0, type: "f32" },
    },
  },
});

sprite.filters = filter;

app.ticker.add((ticker) => {
  filter.resources.timeUniforms.uniforms.uTime += 0.04 * ticker.deltaTime;
});
```

For more control, construct `GlProgram`/`GpuProgram` objects directly