43 lines
1.3 KiB
TypeScript
43 lines
1.3 KiB
TypeScript
import decodePng from "png-chunks-extract";
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import tEXt from "png-chunk-text";
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import encodePng from "png-chunks-encode";
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const blobToArrayBuffer = (blob: Blob): Promise<ArrayBuffer> => {
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if ("arrayBuffer" in blob) {
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return blob.arrayBuffer();
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}
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// Safari
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return new Promise((resolve, reject) => {
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const reader = new FileReader();
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reader.onload = (event) => {
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if (!event.target?.result) {
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return reject(new Error("couldn't convert blob to ArrayBuffer"));
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}
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resolve(event.target.result as ArrayBuffer);
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};
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reader.readAsArrayBuffer(blob);
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});
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};
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export const getTEXtChunk = async (
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blob: Blob,
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): Promise<{ keyword: string; text: string } | null> => {
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const chunks = decodePng(new Uint8Array(await blobToArrayBuffer(blob)));
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const metadataChunk = chunks.find((chunk) => chunk.name === "tEXt");
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if (metadataChunk) {
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return tEXt.decode(metadataChunk.data);
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}
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return null;
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};
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export const encodeTEXtChunk = async (
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blob: Blob,
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chunk: { keyword: string; text: string },
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): Promise<Blob> => {
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const chunks = decodePng(new Uint8Array(await blobToArrayBuffer(blob)));
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const metadata = tEXt.encode(chunk.keyword, chunk.text);
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// insert metadata before last chunk (iEND)
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chunks.splice(-1, 0, metadata);
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return new Blob([encodePng(chunks)], { type: "image/png" });
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};
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