Refactor image metadata handling for user color embedding

- Updated useUserColor hook to support multiple image formats (PNG, WebP, JPEG, GIF) for color embedding and extraction.
- Introduced unified image metadata utilities in imageMetadata.ts for detecting formats and handling color operations.
- Added GIF metadata utilities in gifMetadata.ts for reading and writing user color.
- Implemented JPEG metadata utilities in jpegMetadata.ts for embedding and extracting user color.
- Created WebP metadata utilities in webpMetadata.ts for handling user color in WebP images.
- Enhanced error handling and logging for unsupported formats and operations.
This commit is contained in:
2026-02-06 15:27:15 +11:00
parent 516000a25f
commit bfbdf98468
5 changed files with 1141 additions and 14 deletions

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/**
* Utilities for reading and writing GIF metadata (Application Extension blocks)
* Used to embed user color in avatar images
*
* GIF structure:
* - Header: GIF87a or GIF89a (6 bytes)
* - Logical Screen Descriptor (7 bytes)
* - Optional Global Color Table
* - Extension blocks and image data
* - Trailer: 0x3B
*
* Application Extension format:
* - 0x21 (Extension Introducer)
* - 0xFF (Application Extension Label)
* - 0x0B (Block size - always 11)
* - 8 bytes: Application Identifier
* - 3 bytes: Application Authentication Code
* - Data sub-blocks (size byte + data, terminated by 0x00)
*/
/* eslint-disable no-bitwise */
/* eslint-disable no-plusplus */
/* eslint-disable no-console */
/* eslint-disable no-restricted-syntax */
/* eslint-disable no-continue */
/** GIF signature bytes */
const GIF87A_SIGNATURE = new Uint8Array([0x47, 0x49, 0x46, 0x38, 0x37, 0x61]); // "GIF87a"
const GIF89A_SIGNATURE = new Uint8Array([0x47, 0x49, 0x46, 0x38, 0x39, 0x61]); // "GIF89a"
/** Our custom application identifier (8 chars) */
const PAARROT_APP_ID = 'PAARROT\0'; // 8 bytes, null-padded
const PAARROT_APP_ID_BYTES = new TextEncoder().encode(PAARROT_APP_ID);
/** Application authentication code (3 bytes) */
const PAARROT_AUTH_CODE = new Uint8Array([0x31, 0x2E, 0x30]); // "1.0"
/**
* Check if data is a valid GIF file
*/
function isGIF(data: Uint8Array): boolean {
if (data.length < 6) return false;
// Check GIF87a
let is87a = true;
for (let i = 0; i < 6; i++) {
if (data[i] !== GIF87A_SIGNATURE[i]) {
is87a = false;
break;
}
}
if (is87a) return true;
// Check GIF89a
let is89a = true;
for (let i = 0; i < 6; i++) {
if (data[i] !== GIF89A_SIGNATURE[i]) {
is89a = false;
break;
}
}
return is89a;
}
/**
* Get the size of the Global Color Table if present
*/
function getGlobalColorTableSize(data: Uint8Array): number {
// Logical Screen Descriptor starts at offset 6
// Packed byte is at offset 10
const packedByte = data[10];
const hasGCT = (packedByte & 0x80) !== 0;
if (!hasGCT) return 0;
const gctSize = packedByte & 0x07;
return 3 * (2 ** (gctSize + 1));
}
/**
* Find all Application Extension blocks
*/
function findAppExtensions(data: Uint8Array, startOffset: number): Array<{
offset: number;
length: number;
appId: string;
authCode: Uint8Array;
dataBlocks: Uint8Array[];
}> {
const extensions: Array<{
offset: number;
length: number;
appId: string;
authCode: Uint8Array;
dataBlocks: Uint8Array[];
}> = [];
let offset = startOffset;
while (offset < data.length - 1) {
// Look for Extension Introducer (0x21)
if (data[offset] === 0x21 && data[offset + 1] === 0xFF) {
// Application Extension
const blockSize = data[offset + 2];
if (blockSize !== 0x0B) {
offset++;
continue;
}
const appId = new TextDecoder().decode(data.slice(offset + 3, offset + 11));
const authCode = data.slice(offset + 11, offset + 14);
// Read data sub-blocks
let subOffset = offset + 14;
const dataBlocks: Uint8Array[] = [];
let totalLength = 14; // header length
while (subOffset < data.length && data[subOffset] !== 0x00) {
const subBlockSize = data[subOffset];
dataBlocks.push(data.slice(subOffset + 1, subOffset + 1 + subBlockSize));
subOffset += 1 + subBlockSize;
totalLength += 1 + subBlockSize;
}
// Add terminator
totalLength += 1;
extensions.push({
offset,
length: totalLength,
appId,
authCode,
dataBlocks,
});
offset = subOffset + 1;
} else if (data[offset] === 0x3B) {
// Trailer - end of GIF
break;
} else {
offset++;
}
}
return extensions;
}
/**
* Create a PAARROT Application Extension block with color data
*/
function createPaarrotExtension(color: string): Uint8Array {
const colorBytes = new TextEncoder().encode(color);
// Calculate total size
// 0x21 + 0xFF + 0x0B + appId(8) + authCode(3) + sub-block(1 + colorBytes.length) + 0x00
const totalSize = 2 + 1 + 8 + 3 + 1 + colorBytes.length + 1;
const extension = new Uint8Array(totalSize);
let offset = 0;
extension[offset++] = 0x21; // Extension Introducer
extension[offset++] = 0xFF; // Application Extension Label
extension[offset++] = 0x0B; // Block size (always 11)
// Application Identifier (8 bytes)
extension.set(PAARROT_APP_ID_BYTES, offset);
offset += 8;
// Application Authentication Code (3 bytes)
extension.set(PAARROT_AUTH_CODE, offset);
offset += 3;
// Data sub-block
extension[offset++] = colorBytes.length;
extension.set(colorBytes, offset);
offset += colorBytes.length;
// Block terminator
extension[offset] = 0x00;
return extension;
}
/**
* Extract paarrot color from GIF image data
*/
export function extractColorFromGIF(imageData: ArrayBuffer | Uint8Array): string | undefined {
const data = imageData instanceof Uint8Array ? imageData : new Uint8Array(imageData);
console.log('[extractColorFromGIF] Input size:', data.length, 'bytes');
if (!isGIF(data)) {
console.error('[extractColorFromGIF] Not a GIF file');
return undefined;
}
const gctSize = getGlobalColorTableSize(data);
const startOffset = 13 + gctSize; // Header(6) + LSD(7) + GCT
const extensions = findAppExtensions(data, startOffset);
console.log('[extractColorFromGIF] Found', extensions.length, 'application extensions');
for (const ext of extensions) {
if (ext.appId.startsWith('PAARROT')) {
if (ext.dataBlocks.length > 0) {
const color = new TextDecoder().decode(ext.dataBlocks[0]);
console.log('[extractColorFromGIF] Found color:', color);
return color;
}
}
}
console.log('[extractColorFromGIF] No color found');
return undefined;
}
/**
* Embed paarrot color into GIF image data
*/
export function embedColorInGIF(imageData: ArrayBuffer | Uint8Array, color: string): Uint8Array | null {
const data = imageData instanceof Uint8Array ? imageData : new Uint8Array(imageData);
console.log('[embedColorInGIF] Input size:', data.length, 'bytes');
if (!isGIF(data)) {
console.error('[embedColorInGIF] Not a GIF file');
return null;
}
const gctSize = getGlobalColorTableSize(data);
const insertOffset = 13 + gctSize; // After Header + LSD + GCT
const extensions = findAppExtensions(data, insertOffset);
console.log('[embedColorInGIF] Found', extensions.length, 'application extensions');
// Find existing PAARROT extension
let existingExt: { offset: number; length: number } | null = null;
for (const ext of extensions) {
if (ext.appId.startsWith('PAARROT')) {
existingExt = { offset: ext.offset, length: ext.length };
break;
}
}
// Create new extension
const newExtension = createPaarrotExtension(color);
console.log('[embedColorInGIF] Created extension, size:', newExtension.length, 'bytes');
console.log('[embedColorInGIF] Color being embedded:', color);
let newData: Uint8Array;
if (existingExt) {
// Replace existing extension
console.log('[embedColorInGIF] Replacing existing extension at offset', existingExt.offset);
newData = new Uint8Array(data.length - existingExt.length + newExtension.length);
newData.set(data.slice(0, existingExt.offset), 0);
newData.set(newExtension, existingExt.offset);
newData.set(
data.slice(existingExt.offset + existingExt.length),
existingExt.offset + newExtension.length
);
} else {
// Insert after GCT (before any other blocks)
console.log('[embedColorInGIF] Inserting new extension at offset', insertOffset);
newData = new Uint8Array(data.length + newExtension.length);
newData.set(data.slice(0, insertOffset), 0);
newData.set(newExtension, insertOffset);
newData.set(data.slice(insertOffset), insertOffset + newExtension.length);
}
console.log('[embedColorInGIF] Output size:', newData.length, 'bytes');
return newData;
}
/**
* Remove paarrot color from GIF image data
*/
export function removeColorFromGIF(imageData: ArrayBuffer | Uint8Array): Uint8Array | null {
const data = imageData instanceof Uint8Array ? imageData : new Uint8Array(imageData);
if (!isGIF(data)) {
return null;
}
const gctSize = getGlobalColorTableSize(data);
const startOffset = 13 + gctSize;
const extensions = findAppExtensions(data, startOffset);
// Find existing PAARROT extension
let existingExt: { offset: number; length: number } | null = null;
for (const ext of extensions) {
if (ext.appId.startsWith('PAARROT')) {
existingExt = { offset: ext.offset, length: ext.length };
break;
}
}
if (!existingExt) {
return data;
}
// Remove the extension
const newData = new Uint8Array(data.length - existingExt.length);
newData.set(data.slice(0, existingExt.offset), 0);
newData.set(
data.slice(existingExt.offset + existingExt.length),
existingExt.offset
);
return newData;
}

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/**
* Unified image metadata utilities for embedding/extracting user color
* Supports PNG, WebP, JPEG, and GIF formats
*/
/* eslint-disable no-plusplus */
/* eslint-disable no-console */
import { embedColorInPNG, extractColorFromPNG, removeColorFromPNG } from './pngMetadata';
import { embedColorInWebP, extractColorFromWebP, removeColorFromWebP } from './webpMetadata';
import { embedColorInJPEG, extractColorFromJPEG, removeColorFromJPEG } from './jpegMetadata';
import { embedColorInGIF, extractColorFromGIF, removeColorFromGIF } from './gifMetadata';
/** PNG signature bytes */
const PNG_SIGNATURE = [137, 80, 78, 71, 13, 10, 26, 10];
/** RIFF/WebP signature bytes */
const RIFF_SIGNATURE = [0x52, 0x49, 0x46, 0x46]; // "RIFF"
const WEBP_OFFSET_SIGNATURE = [0x57, 0x45, 0x42, 0x50]; // "WEBP" at offset 8
/** JPEG signature */
const JPEG_SIGNATURE = [0xFF, 0xD8];
/** GIF signatures */
const GIF87A_SIGNATURE = [0x47, 0x49, 0x46, 0x38, 0x37, 0x61]; // "GIF87a"
const GIF89A_SIGNATURE = [0x47, 0x49, 0x46, 0x38, 0x39, 0x61]; // "GIF89a"
export type ImageFormat = 'png' | 'webp' | 'jpeg' | 'gif' | 'unknown';
/**
* Detect image format from raw data
*/
export function detectImageFormat(data: ArrayBuffer | Uint8Array): ImageFormat {
const bytes = data instanceof Uint8Array ? data : new Uint8Array(data);
if (bytes.length < 12) return 'unknown';
// Check PNG signature
let isPNG = true;
for (let i = 0; i < 8; i++) {
if (bytes[i] !== PNG_SIGNATURE[i]) {
isPNG = false;
break;
}
}
if (isPNG) return 'png';
// Check WebP signature (RIFF + WEBP)
let isRIFF = true;
for (let i = 0; i < 4; i++) {
if (bytes[i] !== RIFF_SIGNATURE[i]) {
isRIFF = false;
break;
}
}
if (isRIFF) {
let isWebP = true;
for (let i = 0; i < 4; i++) {
if (bytes[8 + i] !== WEBP_OFFSET_SIGNATURE[i]) {
isWebP = false;
break;
}
}
if (isWebP) return 'webp';
}
// Check JPEG signature (FFD8)
if (bytes[0] === JPEG_SIGNATURE[0] && bytes[1] === JPEG_SIGNATURE[1]) {
return 'jpeg';
}
// Check GIF signatures
let isGIF87a = true;
for (let i = 0; i < 6; i++) {
if (bytes[i] !== GIF87A_SIGNATURE[i]) {
isGIF87a = false;
break;
}
}
if (isGIF87a) return 'gif';
let isGIF89a = true;
for (let i = 0; i < 6; i++) {
if (bytes[i] !== GIF89A_SIGNATURE[i]) {
isGIF89a = false;
break;
}
}
if (isGIF89a) return 'gif';
return 'unknown';
}
/**
* Extract paarrot color from image data (PNG, WebP, JPEG, or GIF)
* @param imageData - Raw image data as ArrayBuffer or Uint8Array
* @returns The color string if found, or undefined
*/
export function extractColorFromImage(imageData: ArrayBuffer | Uint8Array): string | undefined {
const format = detectImageFormat(imageData);
switch (format) {
case 'png':
return extractColorFromPNG(imageData);
case 'webp':
return extractColorFromWebP(imageData);
case 'jpeg':
return extractColorFromJPEG(imageData);
case 'gif':
return extractColorFromGIF(imageData);
default:
console.warn('[extractColorFromImage] Unknown image format');
return undefined;
}
}
/**
* Embed paarrot color into image data (PNG, WebP, JPEG, or GIF)
* @param imageData - Raw image data as ArrayBuffer or Uint8Array
* @param color - The color string to embed (e.g., '#ff5500')
* @returns New image data with embedded color, or null if not a supported format
*/
export function embedColorInImage(imageData: ArrayBuffer | Uint8Array, color: string): Uint8Array | null {
const format = detectImageFormat(imageData);
switch (format) {
case 'png':
return embedColorInPNG(imageData, color);
case 'webp':
return embedColorInWebP(imageData, color);
case 'jpeg':
return embedColorInJPEG(imageData, color);
case 'gif':
return embedColorInGIF(imageData, color);
default:
console.warn('[embedColorInImage] Unknown image format, cannot embed color');
return null;
}
}
/**
* Remove paarrot color from image data (PNG, WebP, JPEG, or GIF)
* @param imageData - Raw image data as ArrayBuffer or Uint8Array
* @returns New image data without the color, or null if not a supported format
*/
export function removeColorFromImage(imageData: ArrayBuffer | Uint8Array): Uint8Array | null {
const format = detectImageFormat(imageData);
switch (format) {
case 'png':
return removeColorFromPNG(imageData);
case 'webp':
return removeColorFromWebP(imageData);
case 'jpeg':
return removeColorFromJPEG(imageData);
case 'gif':
return removeColorFromGIF(imageData);
default:
console.warn('[removeColorFromImage] Unknown image format');
return null;
}
}
/**
* Get the MIME type for an image format
*/
export function getMimeType(format: ImageFormat): string {
switch (format) {
case 'png':
return 'image/png';
case 'webp':
return 'image/webp';
case 'jpeg':
return 'image/jpeg';
case 'gif':
return 'image/gif';
default:
return 'application/octet-stream';
}
}
/**
* Get the file extension for an image format
*/
export function getExtension(format: ImageFormat): string {
switch (format) {
case 'png':
return 'png';
case 'webp':
return 'webp';
case 'jpeg':
return 'jpg';
case 'gif':
return 'gif';
default:
return 'bin';
}
}
/**
* Fetch and extract color from an image URL (supports PNG and WebP)
* @param url - HTTP URL to fetch the image from
* @returns The color string if found, or undefined
*/
export async function fetchAndExtractColor(url: string): Promise<string | undefined> {
try {
const response = await fetch(url);
if (!response.ok) return undefined;
const data = await response.arrayBuffer();
return extractColorFromImage(data);
} catch {
return undefined;
}
}

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/**
* Utilities for reading and writing JPEG metadata (XMP/APP1 segments)
* Used to embed user color in avatar images
*
* JPEG structure:
* - Starts with FFD8 (SOI marker)
* - Contains segments: FF + marker type + length (2 bytes BE) + data
* - APP1 (FFE1) is used for EXIF/XMP data
* - Ends with FFD9 (EOI marker)
*/
/* eslint-disable no-bitwise */
/* eslint-disable no-plusplus */
/* eslint-disable no-console */
/* eslint-disable no-restricted-syntax */
/* eslint-disable no-continue */
/** JPEG signature bytes */
const JPEG_SOI = new Uint8Array([0xFF, 0xD8]); // Start of Image
/** XMP namespace identifier in APP1 segment */
const XMP_NAMESPACE = 'http://ns.adobe.com/xap/1.0/\0';
const XMP_NAMESPACE_BYTES = new TextEncoder().encode(XMP_NAMESPACE);
/** Custom XMP namespace for paarrot */
const PAARROT_XMP_START = '<?xpacket begin="" id="W5M0MpCehiHzreSzNTczkc9d"?>';
const PAARROT_XMP_END = '<?xpacket end="w"?>';
/**
* Check if data is a valid JPEG file
*/
function isJPEG(data: Uint8Array): boolean {
if (data.length < 2) return false;
return data[0] === 0xFF && data[1] === 0xD8;
}
/**
* Read a 16-bit big-endian integer from a buffer
*/
function readUint16BE(data: Uint8Array, offset: number): number {
return (data[offset] << 8) | data[offset + 1];
}
/**
* Write a 16-bit big-endian integer
*/
function writeUint16BE(value: number): Uint8Array {
return new Uint8Array([(value >> 8) & 0xff, value & 0xff]);
}
/**
* Create XMP data containing the color value
*/
function createXMPData(color: string): string {
return `${PAARROT_XMP_START}
<x:xmpmeta xmlns:x="adobe:ns:meta/">
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
<rdf:Description rdf:about="" xmlns:paarrot="http://paarrot.app/ns/1.0/">
<paarrot:color>${color}</paarrot:color>
</rdf:Description>
</rdf:RDF>
</x:xmpmeta>
${PAARROT_XMP_END}`;
}
/**
* Extract color from XMP data
*/
function extractColorFromXMP(xmpData: string): string | undefined {
const match = xmpData.match(/<paarrot:color>([^<]+)<\/paarrot:color>/);
if (match) {
return match[1];
}
return undefined;
}
/**
* Parse JPEG segments
*/
function parseSegments(data: Uint8Array): Array<{ marker: number; data: Uint8Array; offset: number; length: number }> {
const segments: Array<{ marker: number; data: Uint8Array; offset: number; length: number }> = [];
let offset = 2; // Skip SOI marker
while (offset < data.length - 1) {
// Find next marker (0xFF followed by non-zero, non-0xFF byte)
if (data[offset] !== 0xFF) {
offset++;
continue;
}
const marker = data[offset + 1];
// Skip padding bytes (0xFF)
if (marker === 0xFF || marker === 0x00) {
offset++;
continue;
}
// EOI (End of Image) or SOS (Start of Scan) - stop parsing
if (marker === 0xD9 || marker === 0xDA) {
break;
}
// Markers without length field (RST0-RST7, SOI, EOI)
if ((marker >= 0xD0 && marker <= 0xD7) || marker === 0xD8 || marker === 0xD9) {
offset += 2;
continue;
}
// Read segment length (includes the 2 length bytes)
const segmentLength = readUint16BE(data, offset + 2);
const segmentData = data.slice(offset + 4, offset + 2 + segmentLength);
segments.push({
marker,
data: segmentData,
offset,
length: 2 + segmentLength, // marker (2) + length field + data
});
offset += 2 + segmentLength;
}
return segments;
}
/**
* Check if APP1 segment contains paarrot XMP data
*/
function isPaarrotXMP(segmentData: Uint8Array): boolean {
// Check for XMP namespace
if (segmentData.length < XMP_NAMESPACE_BYTES.length) return false;
for (let i = 0; i < XMP_NAMESPACE_BYTES.length; i++) {
if (segmentData[i] !== XMP_NAMESPACE_BYTES[i]) return false;
}
const xmpString = new TextDecoder().decode(segmentData.slice(XMP_NAMESPACE_BYTES.length));
return xmpString.includes('paarrot:color') || xmpString.includes('paarrot.app');
}
/**
* Extract paarrot color from JPEG image data
*/
export function extractColorFromJPEG(imageData: ArrayBuffer | Uint8Array): string | undefined {
const data = imageData instanceof Uint8Array ? imageData : new Uint8Array(imageData);
console.log('[extractColorFromJPEG] Input size:', data.length, 'bytes');
if (!isJPEG(data)) {
console.error('[extractColorFromJPEG] Not a JPEG file');
return undefined;
}
const segments = parseSegments(data);
console.log('[extractColorFromJPEG] Found', segments.length, 'segments');
for (const segment of segments) {
// APP1 marker (0xE1) is used for XMP
if (segment.marker === 0xE1) {
// Check for XMP namespace
if (segment.data.length >= XMP_NAMESPACE_BYTES.length) {
let isXMP = true;
for (let i = 0; i < XMP_NAMESPACE_BYTES.length; i++) {
if (segment.data[i] !== XMP_NAMESPACE_BYTES[i]) {
isXMP = false;
break;
}
}
if (isXMP) {
const xmpString = new TextDecoder().decode(segment.data.slice(XMP_NAMESPACE_BYTES.length));
const color = extractColorFromXMP(xmpString);
if (color) {
console.log('[extractColorFromJPEG] Found color:', color);
return color;
}
}
}
}
}
console.log('[extractColorFromJPEG] No color found');
return undefined;
}
/**
* Embed paarrot color into JPEG image data
*/
export function embedColorInJPEG(imageData: ArrayBuffer | Uint8Array, color: string): Uint8Array | null {
const data = imageData instanceof Uint8Array ? imageData : new Uint8Array(imageData);
console.log('[embedColorInJPEG] Input size:', data.length, 'bytes');
if (!isJPEG(data)) {
console.error('[embedColorInJPEG] Not a JPEG file');
return null;
}
const segments = parseSegments(data);
console.log('[embedColorInJPEG] Found', segments.length, 'segments');
// Find existing paarrot XMP segment
let existingSegment: { offset: number; length: number } | null = null;
for (const segment of segments) {
if (segment.marker === 0xE1 && isPaarrotXMP(segment.data)) {
existingSegment = { offset: segment.offset, length: segment.length };
break;
}
}
// Create XMP APP1 segment
const xmpData = createXMPData(color);
const xmpBytes = new TextEncoder().encode(xmpData);
const segmentData = new Uint8Array(XMP_NAMESPACE_BYTES.length + xmpBytes.length);
segmentData.set(XMP_NAMESPACE_BYTES, 0);
segmentData.set(xmpBytes, XMP_NAMESPACE_BYTES.length);
// APP1 segment: FF E1 + length (2 bytes) + data
const segmentLength = 2 + segmentData.length; // length field + data
const app1Segment = new Uint8Array(4 + segmentData.length);
app1Segment[0] = 0xFF;
app1Segment[1] = 0xE1;
app1Segment.set(writeUint16BE(segmentLength), 2);
app1Segment.set(segmentData, 4);
console.log('[embedColorInJPEG] Created APP1 segment, size:', app1Segment.length, 'bytes');
console.log('[embedColorInJPEG] Color being embedded:', color);
let newData: Uint8Array;
if (existingSegment) {
// Replace existing segment
console.log('[embedColorInJPEG] Replacing existing segment at offset', existingSegment.offset);
newData = new Uint8Array(data.length - existingSegment.length + app1Segment.length);
newData.set(data.slice(0, existingSegment.offset), 0);
newData.set(app1Segment, existingSegment.offset);
newData.set(
data.slice(existingSegment.offset + existingSegment.length),
existingSegment.offset + app1Segment.length
);
} else {
// Insert after SOI marker (at offset 2)
console.log('[embedColorInJPEG] Inserting new segment after SOI');
newData = new Uint8Array(data.length + app1Segment.length);
newData.set(JPEG_SOI, 0);
newData.set(app1Segment, 2);
newData.set(data.slice(2), 2 + app1Segment.length);
}
console.log('[embedColorInJPEG] Output size:', newData.length, 'bytes');
return newData;
}
/**
* Remove paarrot color from JPEG image data
*/
export function removeColorFromJPEG(imageData: ArrayBuffer | Uint8Array): Uint8Array | null {
const data = imageData instanceof Uint8Array ? imageData : new Uint8Array(imageData);
if (!isJPEG(data)) {
return null;
}
const segments = parseSegments(data);
// Find existing paarrot XMP segment
let existingSegment: { offset: number; length: number } | null = null;
for (const segment of segments) {
if (segment.marker === 0xE1 && isPaarrotXMP(segment.data)) {
existingSegment = { offset: segment.offset, length: segment.length };
break;
}
}
if (!existingSegment) {
return data;
}
// Remove the segment
const newData = new Uint8Array(data.length - existingSegment.length);
newData.set(data.slice(0, existingSegment.offset), 0);
newData.set(
data.slice(existingSegment.offset + existingSegment.length),
existingSegment.offset
);
return newData;
}

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/**
* Utilities for reading and writing WebP metadata (custom XMP chunks)
* Used to embed user color in avatar images
*
* WebP uses RIFF container format:
* - File starts with "RIFF" (4 bytes) + file size (4 bytes LE) + "WEBP" (4 bytes)
* - Chunks: chunk ID (4 bytes) + chunk size (4 bytes LE) + chunk data (+ padding byte if odd size)
*/
/* eslint-disable no-bitwise */
/* eslint-disable no-plusplus */
/* eslint-disable no-console */
/* eslint-disable no-restricted-syntax */
/** RIFF signature bytes */
const RIFF_SIGNATURE = new Uint8Array([0x52, 0x49, 0x46, 0x46]); // "RIFF"
const WEBP_SIGNATURE = new Uint8Array([0x57, 0x45, 0x42, 0x50]); // "WEBP"
/** Key used to store user color in metadata */
export const PAARROT_COLOR_KEY = 'paarrot:color';
/** Custom chunk ID for paarrot color - using XMP_ as it's a standard metadata chunk */
const XMP_CHUNK_ID = new Uint8Array([0x58, 0x4D, 0x50, 0x20]); // "XMP "
/**
* Read a 32-bit little-endian integer from a buffer
*/
function readUint32LE(data: Uint8Array, offset: number): number {
return data[offset] | (data[offset + 1] << 8) | (data[offset + 2] << 16) | (data[offset + 3] << 24);
}
/**
* Write a 32-bit little-endian integer to a buffer
*/
function writeUint32LE(value: number): Uint8Array {
return new Uint8Array([
value & 0xff,
(value >> 8) & 0xff,
(value >> 16) & 0xff,
(value >> 24) & 0xff,
]);
}
/**
* Check if data is a valid WebP file
*/
function isWebP(data: Uint8Array): boolean {
if (data.length < 12) return false;
// Check RIFF signature
for (let i = 0; i < 4; i++) {
if (data[i] !== RIFF_SIGNATURE[i]) return false;
}
// Check WEBP signature at offset 8
for (let i = 0; i < 4; i++) {
if (data[8 + i] !== WEBP_SIGNATURE[i]) return false;
}
return true;
}
/**
* Create XMP data containing the color value
*/
function createXMPData(color: string): string {
return `<?xpacket begin="" id="W5M0MpCehiHzreSzNTczkc9d"?>
<x:xmpmeta xmlns:x="adobe:ns:meta/">
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
<rdf:Description rdf:about="" xmlns:paarrot="http://paarrot.app/ns/1.0/">
<paarrot:color>${color}</paarrot:color>
</rdf:Description>
</rdf:RDF>
</x:xmpmeta>
<?xpacket end="w"?>`;
}
/**
* Extract color from XMP data
*/
function extractColorFromXMP(xmpData: string): string | undefined {
// Look for paarrot:color tag
const match = xmpData.match(/<paarrot:color>([^<]+)<\/paarrot:color>/);
if (match) {
return match[1];
}
return undefined;
}
/**
* Parse WebP chunks from image data
*/
function parseChunks(data: Uint8Array): Array<{ id: string; data: Uint8Array; offset: number; length: number }> {
const chunks: Array<{ id: string; data: Uint8Array; offset: number; length: number }> = [];
let offset = 12; // Skip RIFF header (4) + size (4) + WEBP (4)
while (offset + 8 <= data.length) {
const id = new TextDecoder().decode(data.slice(offset, offset + 4));
const size = readUint32LE(data, offset + 4);
const chunkData = data.slice(offset + 8, offset + 8 + size);
// Chunk length includes padding byte if size is odd
const paddedSize = size + (size % 2);
chunks.push({
id,
data: chunkData,
offset,
length: 8 + paddedSize, // header (8) + data + optional padding
});
offset += 8 + paddedSize;
}
return chunks;
}
/**
* Extract paarrot color from WebP image data
* @param imageData - Raw WebP image data as ArrayBuffer or Uint8Array
* @returns The color string if found, or undefined
*/
export function extractColorFromWebP(imageData: ArrayBuffer | Uint8Array): string | undefined {
const data = imageData instanceof Uint8Array ? imageData : new Uint8Array(imageData);
console.log('[extractColorFromWebP] Input size:', data.length, 'bytes');
if (!isWebP(data)) {
console.error('[extractColorFromWebP] Not a WebP file');
return undefined;
}
const chunks = parseChunks(data);
console.log('[extractColorFromWebP] Found', chunks.length, 'chunks:', chunks.map(c => c.id).join(', '));
for (const chunk of chunks) {
if (chunk.id === 'XMP ') {
const xmpString = new TextDecoder().decode(chunk.data);
const color = extractColorFromXMP(xmpString);
if (color) {
console.log('[extractColorFromWebP] Found color:', color);
return color;
}
}
}
console.log('[extractColorFromWebP] No color found');
return undefined;
}
/**
* Embed paarrot color into WebP image data
* @param imageData - Raw WebP image data as ArrayBuffer or Uint8Array
* @param color - The color string to embed (e.g., '#ff5500')
* @returns New WebP data with embedded color, or null if not a valid WebP
*/
export function embedColorInWebP(imageData: ArrayBuffer | Uint8Array, color: string): Uint8Array | null {
const data = imageData instanceof Uint8Array ? imageData : new Uint8Array(imageData);
console.log('[embedColorInWebP] Input size:', data.length, 'bytes');
if (!isWebP(data)) {
console.error('[embedColorInWebP] Not a WebP file');
return null;
}
const chunks = parseChunks(data);
console.log('[embedColorInWebP] Found', chunks.length, 'chunks:', chunks.map(c => c.id).join(', '));
// Find existing XMP chunk with our color
let existingXMPChunk: { offset: number; length: number } | null = null;
for (const chunk of chunks) {
if (chunk.id === 'XMP ') {
const xmpString = new TextDecoder().decode(chunk.data);
if (xmpString.includes('paarrot:color') || xmpString.includes('paarrot.app')) {
existingXMPChunk = { offset: chunk.offset, length: chunk.length };
break;
}
}
}
// Create XMP chunk with color
const xmpData = createXMPData(color);
const xmpBytes = new TextEncoder().encode(xmpData);
const xmpPaddedSize = xmpBytes.length + (xmpBytes.length % 2); // Add padding byte if odd
// XMP chunk: ID (4) + size (4) + data + optional padding
const xmpChunk = new Uint8Array(8 + xmpPaddedSize);
xmpChunk.set(XMP_CHUNK_ID, 0);
xmpChunk.set(writeUint32LE(xmpBytes.length), 4);
xmpChunk.set(xmpBytes, 8);
// Padding byte is already 0 from Uint8Array initialization
console.log('[embedColorInWebP] Created XMP chunk, size:', xmpChunk.length, 'bytes');
console.log('[embedColorInWebP] Color being embedded:', color);
let newData: Uint8Array;
if (existingXMPChunk) {
// Replace existing chunk
console.log('[embedColorInWebP] Replacing existing XMP chunk at offset', existingXMPChunk.offset);
newData = new Uint8Array(data.length - existingXMPChunk.length + xmpChunk.length);
newData.set(data.slice(0, existingXMPChunk.offset), 0);
newData.set(xmpChunk, existingXMPChunk.offset);
newData.set(
data.slice(existingXMPChunk.offset + existingXMPChunk.length),
existingXMPChunk.offset + xmpChunk.length
);
} else {
// Insert new chunk at end (before any trailing data)
console.log('[embedColorInWebP] Inserting new XMP chunk at end');
newData = new Uint8Array(data.length + xmpChunk.length);
newData.set(data, 0);
newData.set(xmpChunk, data.length);
}
// Update RIFF file size (at offset 4)
const newFileSize = newData.length - 8; // RIFF size excludes first 8 bytes
newData.set(writeUint32LE(newFileSize), 4);
console.log('[embedColorInWebP] Output size:', newData.length, 'bytes');
return newData;
}
/**
* Remove paarrot color from WebP image data
* @param imageData - Raw WebP image data as ArrayBuffer or Uint8Array
* @returns New WebP data without the color chunk, or null if not a valid WebP
*/
export function removeColorFromWebP(imageData: ArrayBuffer | Uint8Array): Uint8Array | null {
const data = imageData instanceof Uint8Array ? imageData : new Uint8Array(imageData);
if (!isWebP(data)) {
return null;
}
const chunks = parseChunks(data);
// Find existing XMP chunk with our color
let existingXMPChunk: { offset: number; length: number } | null = null;
for (const chunk of chunks) {
if (chunk.id === 'XMP ') {
const xmpString = new TextDecoder().decode(chunk.data);
if (xmpString.includes('paarrot:color') || xmpString.includes('paarrot.app')) {
existingXMPChunk = { offset: chunk.offset, length: chunk.length };
break;
}
}
}
if (!existingXMPChunk) {
// No color to remove
return data;
}
// Build new WebP data without the XMP chunk
const newData = new Uint8Array(data.length - existingXMPChunk.length);
newData.set(data.slice(0, existingXMPChunk.offset), 0);
newData.set(
data.slice(existingXMPChunk.offset + existingXMPChunk.length),
existingXMPChunk.offset
);
// Update RIFF file size
const newFileSize = newData.length - 8;
newData.set(writeUint32LE(newFileSize), 4);
return newData;
}
/**
* Fetch and extract color from a WebP URL
* @param url - HTTP URL to fetch the WebP from
* @returns The color string if found, or undefined
*/
export async function fetchAndExtractColorFromWebP(url: string): Promise<string | undefined> {
try {
const response = await fetch(url);
if (!response.ok) return undefined;
const data = await response.arrayBuffer();
return extractColorFromWebP(data);
} catch {
return undefined;
}
}