---
title: "Custom Filter with Secondary Texture Input"
description: "This example demonstrates how to create a multi-pass custom filter that uses a secondary image as a strength map to selectively control blur intensity across a Game Object."
phaser: "4.1.0"
size: "1280x720"
files: 1
url: https://phaser.io/oss/examples/v4.1.0/filters/view/custom-filter-with-image-input
site: Phaser - https://phaser.io
---

> This page is about the open-source Phaser framework, for writing a game's code by hand. To make a game with AI, use Phaser AE (https://phaser.io/): the desk's tools work with Web MCP, and the CLI works with your own coding agent. See "For AI agents: Phaser AE" at the end of this page.

# Custom Filter with Secondary Texture Input

This example demonstrates how to create a multi-pass custom filter that uses a secondary image as a strength map to selectively control blur intensity across a Game Object.

A Phaser 4.1.0 example in [Filters](https://phaser.io/oss/examples/v4.1.0/filters.md). It runs at 1280 × 720, and loads its assets from https://cdn.phaserfiles.com/v410. See it running, with its code, at https://phaser.io/oss/examples/v4.1.0/filters/view/custom-filter-with-image-input.

To run it, load Phaser 4.1.0 (`https://cdn.jsdelivr.net/npm/phaser@4.1.0/dist/phaser.min.js`), then the file, on a page with a `<div id="game-container">`.

## Code

### custom filter with image input.js

```js
// Define custom filter.

// This is a complex example of a custom filter which uses multiple passes
// and samples an image texture to control blur levels.
// This is a simplified version of the Blur filter, with extra texture input.

// The Controller is the main interface for the filter.
class BlurByTexture extends Phaser.Filters.Controller
{
    constructor (camera, x, y, steps, strengthMap)
    {
        // The name 'FilterBlurByTexture' is defined in FilterBlurByTexture.
        super(camera, 'FilterBlurByTexture');

        if (x === undefined) { x = 1; }
        if (y === undefined) { y = 1; }
        if (steps === undefined) { steps = 4; }
        if (strengthMap === undefined) { strengthMap = '__WHITE'; }

        // Properties on the controller are used to pass data to the shader.
        this.x = x;
        this.y = y;
        this.steps = steps;
        this.strengthMap = strengthMap;
    }
}

// This RenderNode is required for rendering the custom filter.
// Note that this doesn't use BaseFilterShader.
// It calls additional RenderNodes instead.
class FilterBlurByTexture extends Phaser.Renderer.WebGL.RenderNodes.BaseFilter
{
    constructor (manager)
    {
        // The name 'FilterBlurByTexture' is used by the Controller.
        // Because this is a BaseFilter, we don't need to pass the fragment shader.
        super('FilterBlurByTexture', manager);
    }
    
    // This method is called when the filter is run.
    // When extending BaseFilter, this method must be implemented.
    run (controller, inputDrawingContext, outputDrawingContext, padding)
    {
        // This method must be called when the filter is run.
        this.onRunBegin(outputDrawingContext);

        // Padding must be defined for the filter to work.
        // The base Controller returns a default padding of 0 on all sides.
        if (!padding)
        {
            padding = controller.getPadding();
        }


        // We define a proxy controller so we can modify it without affecting the original.
        var proxyController = {
            camera: controller.camera,
            x: controller.x,
            y: controller.y,
            steps: controller.steps,
            strengthMap: controller.strengthMap
        };

        var currentContext = inputDrawingContext;
        var filter = this.manager.getNode('FilterBlurByTexturePass');
        var steps = controller.steps;

        for (var i = 0; i < steps; i++)
        {
            /*
            Render alternating horizontal and vertical passes.
            Gaussian blurs are axis-separable,
            so this creates the same effect as a single pass with more samples,
            but is faster.
            We have to break this down into steps at this level
            because GLSL doesn't support a variable number of loop iterations,
            so we can't pass the number of steps as a uniform.
            */

            // Horizontal pass
            proxyController.x = controller.x;
            proxyController.y = 0;
            currentContext = filter.run(proxyController, currentContext, null, padding);

            if (i === 0)
            {
                // Stop adding padding after the first pass.
                padding = new Phaser.Geom.Rectangle();
            }

            // Vertical pass
            var output = (i === steps - 1) ? outputDrawingContext : null;
            proxyController.x = 0;
            proxyController.y = controller.y;
            currentContext = filter.run(proxyController, currentContext, output, padding);
        }

        outputDrawingContext = currentContext;


        // This method must be called when the filter is run.
        this.onRunEnd(outputDrawingContext);

        // The method must return the output drawing context.
        return outputDrawingContext;
    }
}

// The fragment shader for the filter.
const fragmentShaderBlurByTexture =
`
// BLUR_BY_TEXTURE_FS
#pragma phaserTemplate(shaderName)

precision mediump float;

uniform sampler2D uMainSampler;
uniform sampler2D strengthMap;
uniform vec2 resolution;
uniform vec2 offset;

varying vec2 outTexCoord;

void main ()
{
    vec2 uv = outTexCoord;

    vec4 strengthSample = texture2D(strengthMap, uv);
    float strength = (strengthSample.r + strengthSample.g + strengthSample.b) / 3.0;

    vec4 col = vec4(0.0);

    vec2 offset = vec2(1.333) * offset * strength;

    col += texture2D(uMainSampler, uv) * 0.29411764705882354;
    col += texture2D(uMainSampler, uv + (offset / resolution)) * 0.35294117647058826;
    col += texture2D(uMainSampler, uv - (offset / resolution)) * 0.35294117647058826;

    gl_FragColor = col;
}
`;

class FilterBlurByTexturePass extends Phaser.Renderer.WebGL.RenderNodes.BaseFilterShader
{
    constructor (manager)
    {
        // The name 'FilterBlurByTexturePass' is used by the FilterBlurByTexture node to access this node.
        super('FilterBlurByTexturePass', manager, null, fragmentShaderBlurByTexture);
    }

    // This method adds extra textures to the shader.
    // `textures` is an array of WebGLTextureWrapper objects.
    // `textures[0]` is always the framebuffer being filtered.
    setupTextures (controller, textures)
    {
        textures[1] = controller.camera.scene.sys.textures.getFrame(controller.strengthMap).glTexture;
    }

    setupUniforms (controller, drawingContext)
    {
        var programManager = this.programManager;

        // Tell the shader which texture unit to use.
        programManager.setUniform('strengthMap', 1);

        programManager.setUniform('resolution', [ drawingContext.width, drawingContext.height ]);
        programManager.setUniform('offset', [ controller.x, controller.y ]);
    }
}

// End custom filter definition.


class Example extends Phaser.Scene
{
    preload ()
    {
        this.load.setBaseURL('https://cdn.phaserfiles.com/v410');
        this.load.image('skull-and-bones', 'assets/pics/skull-and-bones.jpg');
        this.load.image('distortion5', 'assets/textures/distortion5.png');
    }

    create ()
    {
        if (!this.renderer.renderNodes.hasNode('FilterBlurByTexture'))
        {
            // Load the custom filter.
            // We load during scene creation because the renderer has booted by this point.
            this.renderer.renderNodes.addNodeConstructor('FilterBlurByTexture', FilterBlurByTexture);
            this.renderer.renderNodes.addNodeConstructor('FilterBlurByTexturePass', FilterBlurByTexturePass);
        }

        // Add an image to selectively blur.
        const image = this.add.image(640, 360, 'skull-and-bones')
        image.setScale(this.scale.width / image.width);
        image.enableFilters();
        const blurByTexture = image.filters.internal.add(
            new BlurByTexture(image.filterCamera, 4, 4, 4, 'distortion5')
        );

        // Tween the blur strength.
        this.tweens.add({
            targets: blurByTexture,
            x: 0,
            y: 0,
            duration: 3000,
            yoyo: true,
            repeat: -1
        });
    }
}

const config = {
    scale: { mode: Phaser.Scale.FIT },
    type: Phaser.AUTO,
    width: 1280,
    height: 720,
    backgroundColor: '#000000',
    parent: 'game-container',
    scene: Example
};

let game = new Phaser.Game(config);
```

## More in Filters

- [Additive Blend Highlighting](https://phaser.io/oss/examples/v4.1.0/filters/blend/view/blend-add-highlight-object.md): Demonstrates creating glow and highlight effects by applying additive blend filters to Render Textures, including color channel manipulation and tweening filter intensity.
- [Blocky Pixel Filter](https://phaser.io/oss/examples/v4.1.0/filters/blocky/view/blocky-pixels.md): Demonstrates applying a pixelation effect to the camera using the Blocky filter, including how to toggle the effect active state via user input.
- [Bloom Filter Impact Effect](https://phaser.io/oss/examples/v4.1.0/filters/bloom/view/destroy-planet-bloom-filter.md): Demonstrates how to apply and animate a bloom filter on game objects. When a bullet hits the planet, a tween increases the bloom's blur strength to create a glowing impact visual.
- [Bloom with Parallel Filters](https://phaser.io/oss/examples/v4.1.0/filters/parallel%20filters/view/bloom-with-parallel-filters.md): Demonstrates how to create a custom bloom effect by processing a camera through parallel filter tracks, applying threshold and blur filters to one track, and blending it back using additive blending.
- [Combine Color Matrix Alpha Transfer](https://phaser.io/oss/examples/v4.1.0/filters/combine%20color%20matrix/view/combine-color-matrix.md): Demonstrates how to use the Combine Color Matrix filter to map the brightness data of one texture onto the alpha channel of another, including how to invert the resulting alpha.
- [Container Composite Alpha](https://phaser.io/oss/examples/v4.1.0/filters/view/composite-alpha-demo.md): Demonstrates the difference between standard alpha and composite alpha in containers. Setting 'filtersForceComposite' ensures a container renders as a flattened layer, preventing overlapping child elements from showing through each other.
- [Creating a Custom Shader Filter](https://phaser.io/oss/examples/v4.1.0/filters/view/custom-filter.md): Demonstrates how to create and apply a custom WebGL filter by defining a fragment shader, a Filter Controller, and a RenderNode to convert a bump map into a normal map in real-time.
- [Custom Shine Filter](https://phaser.io/oss/examples/v4.1.0/filters/view/custom-shine-filter.md): Learn how to apply a custom external shine filter effect to a Game Object using a specialized render node controller.
- [Custom Shine Filter with Progress Control](https://phaser.io/oss/examples/v4.1.0/filters/view/custom-shine-filter-with-progress-control.md): Demonstrates applying a custom shine filter to an image and manually controlling its animation progress using a tween.
- [Filter Sampler](https://phaser.io/oss/examples/v4.1.0/filters/sampler/view/sampler.md): Demonstrates how to use the Sampler filter to retrieve color data from a specific pixel coordinate on an image, using the result to update the game background color.
- [Panorama Blur Filter](https://phaser.io/oss/examples/v4.1.0/filters/panorama%20blur/view/panorama-blur.md): Use the Panorama Blur filter to pre-render blurred environment maps and apply them to normal-mapped sprites via the Image Light filter.
- [Sprite Filter Auto-Focus](https://phaser.io/oss/examples/v4.1.0/filters/view/auto-focus-filter-demo.md): Demonstrates how filters automatically adapt to transformed Game Objects. This example applies color shifts and dynamic motion blur to multiple rotating and moving sprites.
- [All 14 examples in Filters](https://phaser.io/oss/examples/v4.1.0/filters.md)

---

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