glFilters - v0.6.0

glFilters

GPU-accelerated image filters using WebGL shaders. Every filter runs as a fragment shader — no CPU pixel loops.

Install

npm install webgl-filters

Usage

import { glFilters, brightness, saturate, blur, invert, customShader } from "webgl-filters";

// Build a filter chain and apply it to an image
const result = glFilters()
  .addFilter(brightness({ amount: 0.1 }))
  .addFilter(saturate({ factor: 1.5 }))
  .addFilter(blur())
  .apply(imageData);
// result is { data: Uint8ClampedArray, width, height }

Video filtering

Use .compile() to cache shader programs, then .apply() a <video> element. This renders to a canvas at full frame rate with no CPU readback. Video processing is not supported server-side, but you can manually apply filters to video frames if desired.

import { glFilters, brightness, blur } from "webgl-filters";

const filter = glFilters()
  .addFilter(brightness({ amount: 0.1 }))
  .addFilter(blur())
  .compile();

const video = document.getElementById("my-video") as HTMLVideoElement;
const canvas = filter.apply(video); // returns a <canvas> with a rAF loop
document.body.appendChild(canvas);

// Later: stop the loop and release GPU resources
filter.stop();
filter.dispose();

.compile() also speeds up batch image processing by reusing compiled shaders:

const filter = glFilters()
  .addFilter(brightness({ amount: 0.1 }))
  .compile();

const r1 = filter.apply(image1);
const r2 = filter.apply(image2);
filter.dispose();

Providing your own WebGL context

The gl parameter is optional. If omitted, a canvas and context are created automatically. You can still pass one explicitly:

const gl = canvas.getContext("webgl");
const result = glFilters(gl)
  .addFilter(brightness({ amount: 0.1 }))
  .apply(imageData);

For Node.js (headless), install the gl package:

import createGL from "gl";
const gl = createGL(width, height, { preserveDrawingBuffer: true });

Filters

Filter	Parameters	Description
`alphaUnder({ r, g, b, a? })`	RGBA 0–255 (a defaults to 255)	Composites image over a solid background color
`brightness({ amount })`	`amount`: float (0 = no change)	Adds to RGB channels
`contrast({ factor })`	`factor`: float (1.0 = no change)	Scales around midpoint
`saturate({ factor })`	`factor`: float (1.0 = no change, 0 = grayscale)	Adjusts color saturation
`invert()`	—	Inverts RGB channels
`blur({ radius?, strength? })`	`radius`: px (default 2), `strength`: 0–1 (default 1)	Gaussian blur — radius sets kernel size, strength blends with original
`threshold({ cutoff? })`	`cutoff`: 0–1 (default 0.5)	Binary black/white based on luminance
`dilate({ radius? })`	`radius`: px (default 1)	Morphological dilation — expands bright regions
`erode({ radius? })`	`radius`: px (default 1)	Morphological erosion — shrinks bright regions
`sharpen()`	—	5×5 sharpening
`convolve({ kernel, divisor?, bias? })`	`kernel`: 25-element array	Custom 5×5 convolution
`customShader({ source, uniforms? })`	GLSL source + uniforms	User-defined shader

Custom Shaders

Write GLSL that runs per-pixel. You get these built-in uniforms for free:

u_texture — input image (sampler2D)
v_texCoord — current pixel's texture coordinate (vec2)
u_resolution — image size in pixels (vec2)
u_texelSize — 1.0 / u_resolution (vec2)

const sepia = customShader({
  source: `
    vec4 color = texture2D(u_texture, v_texCoord);
    float grey = dot(color.rgb, vec3(0.299, 0.587, 0.114));
    gl_FragColor = vec4(
      grey + u_tone * 0.2,
      grey + u_tone * 0.05,
      grey - u_tone * 0.15,
      color.a
    );
  `,
  uniforms: { u_tone: 1.0 },
});

License

MIT