speice.io/posts/2023/06/flam3/0-utility.tsx

71 lines
1.7 KiB
TypeScript

import React, { useEffect, useRef } from "react";
export type renderFn = (image: ImageData) => void;
export const Canvas: React.FC<{ f: renderFn }> = ({ f }) => {
const canvasRef = useRef<HTMLCanvasElement | null>(null);
let image: ImageData | null = null;
useEffect(() => {
if (canvasRef.current) {
const canvas = canvasRef.current;
const ctx = canvas.getContext("2d");
if (!ctx) {
return;
}
if (
!image ||
image.width !== canvas.width ||
image.height !== canvas.height
) {
image = ctx.createImageData(canvas.width, canvas.height);
}
f(image);
ctx.putImageData(image, 0, 0);
}
});
return <canvas ref={canvasRef} width={400} height={400} />;
};
export function randomBiUnit() {
// Math.random() produces a number in the range [0, 1),
// scale to (-1, 1)
return Math.random() * 2 - 1;
}
export function randomInteger(min: number, max: number) {
return Math.floor(Math.random() * (max - min)) + min;
}
export function weightedChoice<T>(choices: [number, T][]): [number, T] {
const weightSum = choices.reduce(
(current, [weight, _t]) => current + weight,
0
);
var choice = Math.random() * weightSum;
for (var i = 0; i < choices.length; i++) {
const [weight, t] = choices[i];
if (choice < weight) {
return [i, t];
}
choice -= weight;
}
throw "unreachable";
}
export function imageIndex(x: number, y: number, width: number) {
// Taken from: https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API/Tutorial/Pixel_manipulation_with_canvas
return y * (width * 4) + x * 4;
}
export function histIndex(x: number, y: number, width: number) {
return y * width + x;
}