121 lines
3.4 KiB
TypeScript
121 lines
3.4 KiB
TypeScript
import { deflateSync } from "node:zlib";
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export interface SourceFile {
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name: string;
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mimeType: string;
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buffer: Buffer;
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}
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const CRC_TABLE = (() => {
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const table = new Uint32Array(256);
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for (let n = 0; n < 256; n++) {
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let c = n;
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for (let k = 0; k < 8; k++) c = c & 1 ? 0xedb88320 ^ (c >>> 1) : c >>> 1;
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table[n] = c >>> 0;
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}
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return table;
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})();
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function crc32(data: Uint8Array): number {
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let c = 0xffffffff;
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for (let i = 0; i < data.length; i++)
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c = CRC_TABLE[(c ^ data[i]) & 0xff] ^ (c >>> 8);
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return (c ^ 0xffffffff) >>> 0;
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}
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function chunk(type: string, data: Buffer): Buffer {
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const out = Buffer.alloc(8 + data.length + 4);
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out.writeUInt32BE(data.length, 0);
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out.write(type, 4, "ascii");
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data.copy(out, 8);
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out.writeUInt32BE(crc32(out.subarray(4, 8 + data.length)), 8 + data.length);
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return out;
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}
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/** Строит валидный RGBA PNG в рантайме (8-bit, фильтр type 0, deflate/zlib). */
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export function makePng(
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width: number,
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height: number,
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pixelAt: (x: number, y: number) => [number, number, number, number],
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): Buffer {
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const sig = Buffer.from([137, 80, 78, 71, 13, 10, 26, 10]);
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const ihdr = Buffer.alloc(13);
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ihdr.writeUInt32BE(width, 0);
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ihdr.writeUInt32BE(height, 4);
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ihdr[8] = 8;
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ihdr[9] = 6;
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const stride = width * 4 + 1;
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const raw = Buffer.alloc(height * stride);
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for (let y = 0; y < height; y++) {
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for (let x = 0; x < width; x++) {
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const [r, g, b, a] = pixelAt(x, y);
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const p = y * stride + 1 + x * 4;
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raw[p] = r;
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raw[p + 1] = g;
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raw[p + 2] = b;
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raw[p + 3] = a;
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}
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}
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return Buffer.concat([
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sig,
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chunk("IHDR", ihdr),
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chunk("IDAT", deflateSync(raw)),
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chunk("IEND", Buffer.alloc(0)),
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]);
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}
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const checker = (x: number, y: number): [number, number, number, number] =>
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x % 2 === y % 2 ? [255, 0, 0, 255] : [255, 255, 255, 255];
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const alphaGrid = (x: number, y: number): [number, number, number, number] =>
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(x + y) % 3 === 0 ? [0, 0, 0, 0] : [0, 128, 255, 255];
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const solidRed = (): [number, number, number, number] => [255, 0, 0, 255];
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export function asSourceFile(buffer: Buffer, name: string): SourceFile {
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return { name, mimeType: "image/png", buffer };
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}
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export const opaquePng: SourceFile = asSourceFile(
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makePng(64, 48, checker),
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"opaque.png",
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);
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export const transparentPng: SourceFile = asSourceFile(
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makePng(64, 64, alphaGrid),
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"transparent.png",
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);
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export const onePixelPng: SourceFile = asSourceFile(
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makePng(1, 1, solidRed),
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"1px.png",
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);
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export const landscapePng: SourceFile = asSourceFile(
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makePng(64, 16, checker),
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"landscape.png",
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);
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export const largePng: SourceFile = asSourceFile(
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makePng(256, 256, checker),
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"large.png",
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);
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export const corruptPng: SourceFile = {
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name: "corrupt.png",
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mimeType: "image/png",
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buffer: Buffer.from("this is definitely not a png file", "utf8"),
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};
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export const tinyBase64 = makePng(8, 8, solidRed).toString("base64");
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export const svgMarkup =
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'<svg xmlns="http://www.w3.org/2000/svg" width="10" height="6">' +
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'<rect width="10" height="6" fill="#ff0000"/></svg>';
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const PIXEL_BYTES = (r: number, g: number, b: number, a: number): string =>
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`${r} ${g} ${b} ${a}`;
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/** Строка для bytes-to-png / rgb-values-to-png, ровно 32 пикселя в ширину по умолчанию. */
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export function pixelRow(
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count: number,
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rgba: [number, number, number, number],
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): string {
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return Array.from({ length: count }, () => PIXEL_BYTES(...rgba)).join(" ");
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}
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