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first implementation of itxt on image.ts

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This commit is contained in:
Gabriel Gomes 2025-03-29 20:23:12 +00:00
parent 04d0b00b95
commit 22869ee58c
2 changed files with 63 additions and 19 deletions
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78
packages/excalidraw/data/image.ts
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@ -1,4 +1,5 @@
import tEXt from "png-chunk-text";
import { encode as encodeITXt, decode as decodeITXt } from "png-chunk-itxt";
import encodePng from "png-chunks-encode";
import decodePng from "png-chunks-extract";
@ -11,48 +12,89 @@ import { encode, decode } from "./encode";
// PNG
// -----------------------------------------------------------------------------
export const getTEXtChunk = async (
export const getMetadataChunk = async (
blob: Blob,
): Promise<{ keyword: string; text: string } | null> => {
const chunks = decodePng(new Uint8Array(await blobToArrayBuffer(blob)));
const metadataChunk = chunks.find((chunk) => chunk.name === "tEXt");
if (metadataChunk) {
return tEXt.decode(metadataChunk.data);
const iTXtChunk = chunks.find((chunk) => chunk.name === "iTXt");
if (iTXtChunk) {
try {
const decoded = decodeITXt(iTXtChunk.data);
return { keyword: decoded.keyword, text: decoded.text };
} catch (error) {
console.error("Failed to decode iTXt chunk:", error);
}
}
const tEXtChunk = chunks.find((chunk) => chunk.name === "tEXt");
if (tEXtChunk) {
return tEXt.decode(tEXtChunk.data);
}
return null;
};
export const encodePngMetadata = async ({
blob,
metadata,
useITXt = true,
}: {
blob: Blob;
metadata: string;
useITXt?: boolean;
}) => {
const chunks = decodePng(new Uint8Array(await blobToArrayBuffer(blob)));
const metadataChunk = tEXt.encode(
MIME_TYPES.excalidraw,
JSON.stringify(
encode({
text: metadata,
compress: true,
}),
),
const filteredChunks = chunks.filter(
(chunk) =>
!(chunk.name === "tEXt" &&
tEXt.decode(chunk.data).keyword === MIME_TYPES.excalidraw) &&
!(chunk.name === "iTXt" &&
decodeITXt(chunk.data).keyword === MIME_TYPES.excalidraw)
);
const encodedData = JSON.stringify(
encode({
text: metadata,
compress: true,
}),
);
// insert metadata before last chunk (iEND)
chunks.splice(-1, 0, metadataChunk);
return new Blob([encodePng(chunks)], { type: MIME_TYPES.png });
let metadataChunk;
try {
if (useITXt) {
metadataChunk = encodeITXt(
MIME_TYPES.excalidraw,
encodedData,
{
compressed: false, //Already compressed in encode
language: "en",
translated: ""
}
);
} else {
throw new Error("Fallback to tEXt");
}
} catch (error) {
console.warn("iTXt encoding failed, falling back to tEXt:", error);
metadataChunk = tEXt.encode(
MIME_TYPES.excalidraw,
encodedData,
);
}
filteredChunks.splice(-1, 0, metadataChunk);
return new Blob([encodePng(filteredChunks)], { type: MIME_TYPES.png });
};
export const decodePngMetadata = async (blob: Blob) => {
const metadata = await getTEXtChunk(blob);
const metadata = await getMetadataChunk(blob);
if (metadata?.keyword === MIME_TYPES.excalidraw) {
try {
const encodedData = JSON.parse(metadata.text);
if (!("encoded" in encodedData)) {
// legacy, un-encoded scene JSON
if (
"type" in encodedData &&
encodedData.type === EXPORT_DATA_TYPES.excalidraw