97 lines
2.2 KiB
TypeScript
97 lines
2.2 KiB
TypeScript
export const DEFAULT_SIZE: number = 400;
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/**
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* Image render manager
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*
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* This class tracks the chaos game state so we can periodically
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* get an image.
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*/
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export abstract class Renderer {
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/**
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* Build a render manager. For simplicity, this class assumes
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* we're working with a square image.
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*
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* @param size Image width and height
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*/
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constructor(public readonly size: number) {}
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/**
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* Run the chaos game
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*
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* @param quality iteration count
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*/
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abstract run(quality: number): void;
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/**
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* Output the current chaos game state to image
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*
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* @param image output pixel buffer
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*/
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abstract render(image: ImageData): void;
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}
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export type RenderParams = {
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quality: number;
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renderer: (size: number) => Renderer;
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};
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/**
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* @returns random number in the bi-unit square (-1, 1)
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*/
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export function randomBiUnit() {
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// Math.random() produces a number in the range [0, 1),
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// scale to (-1, 1)
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return Math.random() * 2 - 1;
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}
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/**
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* @returns random integer (with equal weight) in the range [min, max)
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*/
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export function randomInteger(min: number, max: number) {
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return Math.floor(Math.random() * (max - min)) + min;
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}
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/**
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* @param choices array of [weight, value] pairs
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* @returns pair of [index, value]
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*/
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export function weightedChoice<T>(choices: [number, T][]): [number, T] {
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const weightSum = choices.reduce(
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(current, [weight, _t]) => current + weight,
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0
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);
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var choice = Math.random() * weightSum;
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for (var i = 0; i < choices.length; i++) {
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const [weight, t] = choices[i];
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if (choice < weight) {
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return [i, t];
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}
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choice -= weight;
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}
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throw "unreachable";
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}
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/**
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* @param x pixel coordinate
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* @param y pixel coordinate
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* @param width image width
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* @returns index into ImageData buffer for a specific pixel
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*/
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export function imageIndex(x: number, y: number, width: number) {
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// Taken from: https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API/Tutorial/Pixel_manipulation_with_canvas
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return y * (width * 4) + x * 4;
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}
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/**
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* @param x pixel coordinate
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* @param y pixel coordinate
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* @param width image width
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* @returns index into a histogram for a specific pixel
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*/
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export function histIndex(x: number, y: number, width: number) {
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return y * width + x;
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}
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