Source: bulge-pinch/src/BulgePinchFilter.ts

import { vertex } from '@tools/fragments';
import fragment from './bulgePinch.frag';
import { Filter } from '@pixi/core';
import type { Point, Rectangle, FilterSystem, RenderTexture, CLEAR_MODES } from '@pixi/core';

type PointLike = Point | number[];

interface BulgePinchFilterOptions
{
    center: PointLike;
    radius: number;
    strength: number;
}

// @author Julien CLEREL @JuloxRox
// original filter https://github.com/evanw/glfx.js/blob/master/src/filters/warp/bulgepinch.js
// by Evan Wallace : http://madebyevan.com/

/**
 * Bulges or pinches the image in a circle.<br>
 * ![original](../tools/screenshots/dist/original.png)![filter](../tools/screenshots/dist/bulge-pinch.gif)
 *
 * @class
 * @extends PIXI.Filter
 * @see @pixi/filter-bulge-pinch
 * @see pixi-filters
 */
class BulgePinchFilter extends Filter
{
    /** Default constructor options. */
    public static readonly defaults: BulgePinchFilterOptions = {
        center: [0.5, 0.5],
        radius: 100,
        strength: 1,
    };

    /**
     * @param {object} [options] - Options to use for filter.
     * @param {PIXI.Point|Array<number>} [options.center=[0,0]] - The x and y coordinates of the center
     *        of the circle of effect.
     * @param {number} [options.radius=100] - The radius of the circle of effect.
     * @param {number} [options.strength=1] - -1 to 1 (-1 is strong pinch, 0 is no effect, 1 is strong bulge)
     */
    constructor(options?: Partial<BulgePinchFilterOptions>)
    {
        super(vertex, fragment);

        this.uniforms.dimensions = new Float32Array(2);

        Object.assign(this, BulgePinchFilter.defaults, options);
    }

    apply(filterManager: FilterSystem, input: RenderTexture, output: RenderTexture, clear: CLEAR_MODES): void
    {
        const { width, height } = input.filterFrame as Rectangle;

        this.uniforms.dimensions[0] = width;
        this.uniforms.dimensions[1] = height;
        filterManager.applyFilter(this, input, output, clear);
    }

    /**
     * The radius of the circle of effect.
     */
    get radius(): number
    {
        return this.uniforms.radius;
    }
    set radius(value: number)
    {
        this.uniforms.radius = value;
    }

    /**
     * The strength of the effect. -1 to 1 (-1 is strong pinch, 0 is no effect, 1 is strong bulge)
     */
    get strength(): number
    {
        return this.uniforms.strength;
    }
    set strength(value: number)
    {
        this.uniforms.strength = value;
    }

    /**
     * The x and y coordinates of the center of the circle of effect.
     *
     * @member {PIXI.Point | Array<number>}
     */
    get center(): PointLike
    {
        return this.uniforms.center;
    }
    set center(value: PointLike)
    {
        this.uniforms.center = value;
    }
}

export { BulgePinchFilter };
export type { BulgePinchFilterOptions };