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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 | 2x 2x 2x 2x 4x 4x 4x 4x 4x 5x 5x 1x 4x 3x 4x 2x 4x 3x 1x 2x 2x 1x 1x 1x 1x 2x | import { open } from "fs/promises";
export type PNGSize = {
width: number;
height: number;
};
const CGBI_HEADER_SIZE = 40;
const PNG_SIGNATURE = Buffer.from([
0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a,
]);
const readHeader = async (
filename: string,
length: number,
): Promise<Buffer> => {
const file = await open(filename, "r");
try {
const buffer = Buffer.alloc(length);
let offset = 0;
while (offset < length) {
const { bytesRead } = await file.read(
buffer,
offset,
length - offset,
offset,
);
if (bytesRead === 0) {
throw new TypeError("Invalid PNG");
}
offset += bytesRead;
}
return buffer;
} finally {
await file.close();
}
};
export const pngSize = async (filename: string): Promise<PNGSize> => {
const header = await readHeader(filename, CGBI_HEADER_SIZE);
if (!header.subarray(0, PNG_SIGNATURE.length).equals(PNG_SIGNATURE)) {
throw new TypeError("Invalid PNG");
}
const firstChunk = header.toString("ascii", 12, 16);
if (firstChunk === "CgBI") {
Iif (header.toString("ascii", 28, 32) !== "IHDR") {
throw new TypeError("Invalid PNG");
}
return {
width: header.readUInt32BE(32),
height: header.readUInt32BE(36),
};
}
Iif (firstChunk !== "IHDR") {
throw new TypeError("Invalid PNG");
}
return {
width: header.readUInt32BE(16),
height: header.readUInt32BE(20),
};
};
export default pngSize;
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