f0924d3c4e
- Create shared PNG encoder module (src/media/png-encode.ts) - Refactor qr-image.ts and live-image-probe.ts to use shared encoder - Add safeParseJson to utils.ts and plugin-sdk exports - Update msteams and pairing-store to use centralized safeParseJson
91 lines
2.5 KiB
TypeScript
91 lines
2.5 KiB
TypeScript
/**
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* Minimal PNG encoder for generating simple RGBA images without native dependencies.
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* Used for QR codes, live probes, and other programmatic image generation.
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*/
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import { deflateSync } from "node:zlib";
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const CRC_TABLE = (() => {
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const table = new Uint32Array(256);
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for (let i = 0; i < 256; i += 1) {
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let c = i;
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for (let k = 0; k < 8; k += 1) {
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c = c & 1 ? 0xedb88320 ^ (c >>> 1) : c >>> 1;
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}
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table[i] = c >>> 0;
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}
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return table;
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})();
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/** Compute CRC32 checksum for a buffer (used in PNG chunk encoding). */
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export function crc32(buf: Buffer): number {
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let crc = 0xffffffff;
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for (let i = 0; i < buf.length; i += 1) {
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crc = CRC_TABLE[(crc ^ buf[i]) & 0xff] ^ (crc >>> 8);
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}
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return (crc ^ 0xffffffff) >>> 0;
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}
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/** Create a PNG chunk with type, data, and CRC. */
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export function pngChunk(type: string, data: Buffer): Buffer {
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const typeBuf = Buffer.from(type, "ascii");
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const len = Buffer.alloc(4);
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len.writeUInt32BE(data.length, 0);
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const crc = crc32(Buffer.concat([typeBuf, data]));
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const crcBuf = Buffer.alloc(4);
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crcBuf.writeUInt32BE(crc, 0);
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return Buffer.concat([len, typeBuf, data, crcBuf]);
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}
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/** Write a pixel to an RGBA buffer. Ignores out-of-bounds writes. */
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export function fillPixel(
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buf: Buffer,
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x: number,
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y: number,
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width: number,
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r: number,
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g: number,
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b: number,
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a = 255,
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): void {
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if (x < 0 || y < 0 || x >= width) {
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return;
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}
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const idx = (y * width + x) * 4;
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if (idx < 0 || idx + 3 >= buf.length) {
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return;
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}
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buf[idx] = r;
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buf[idx + 1] = g;
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buf[idx + 2] = b;
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buf[idx + 3] = a;
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}
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/** Encode an RGBA buffer as a PNG image. */
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export function encodePngRgba(buffer: Buffer, width: number, height: number): Buffer {
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const stride = width * 4;
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const raw = Buffer.alloc((stride + 1) * height);
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for (let row = 0; row < height; row += 1) {
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const rawOffset = row * (stride + 1);
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raw[rawOffset] = 0; // filter: none
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buffer.copy(raw, rawOffset + 1, row * stride, row * stride + stride);
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}
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const compressed = deflateSync(raw);
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const signature = Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]);
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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; // bit depth
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ihdr[9] = 6; // color type RGBA
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ihdr[10] = 0; // compression
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ihdr[11] = 0; // filter
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ihdr[12] = 0; // interlace
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return Buffer.concat([
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signature,
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pngChunk("IHDR", ihdr),
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pngChunk("IDAT", compressed),
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pngChunk("IEND", Buffer.alloc(0)),
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]);
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}
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