46 lines
1.3 KiB
JavaScript
46 lines
1.3 KiB
JavaScript
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export function getPngMetadata(file) {
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return new Promise((r) => {
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const reader = new FileReader();
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reader.onload = (event) => {
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// Get the PNG data as a Uint8Array
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const pngData = new Uint8Array(event.target.result);
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const dataView = new DataView(pngData.buffer);
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// Check that the PNG signature is present
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if (dataView.getUint32(0) !== 0x89504e47) {
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console.error("Not a valid PNG file");
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r();
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return;
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}
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// Start searching for chunks after the PNG signature
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let offset = 8;
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let txt_chunks = {};
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// Loop through the chunks in the PNG file
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while (offset < pngData.length) {
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// Get the length of the chunk
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const length = dataView.getUint32(offset);
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// Get the chunk type
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const type = String.fromCharCode(...pngData.slice(offset + 4, offset + 8));
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if (type === "tEXt") {
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// Get the keyword
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let keyword_end = offset + 8;
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while (pngData[keyword_end] !== 0) {
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keyword_end++;
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}
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const keyword = String.fromCharCode(...pngData.slice(offset + 8, keyword_end));
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// Get the text
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const text = String.fromCharCode(...pngData.slice(keyword_end + 1, offset + 8 + length));
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txt_chunks[keyword] = text;
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}
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offset += 12 + length;
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}
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r(txt_chunks);
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};
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reader.readAsArrayBuffer(file);
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});
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}
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