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mixedNationalInstituteOfStandardsAndTechnologyReader.ts
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mixedNationalInstituteOfStandardsAndTechnologyReader.ts
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interface Image {
label: number
bitmap: number[][]
}
interface ReadOptions {
encoding?: string
}
async function readFileStr(filename: string, opts: ReadOptions = {}): Promise<string> {
const decoder = new TextDecoder(opts.encoding)
return decoder.decode(await Deno.readFile(filename))
}
export const readDatabase = async () => {
const imagesStream = await readFileStr('./train-images-idx3-ubyte')
const labels = await readFileStr('./train-labels-idx1-ubyte')
if (
imagesStream.charCodeAt(2) !== 8 ||
imagesStream.charCodeAt(3) !== 3 ||
labels.charCodeAt(2) !== 8 ||
labels.charCodeAt(3) !== 1
) {
return
}
const imagesMetadata = Int32Array.from(imagesStream, c => c.codePointAt(0) || 0)
const imagesByteArray = Uint8Array.from(imagesStream, c => c.codePointAt(0) || 0)
const labelsByteArray = Uint8Array.from(labels, c => c.codePointAt(0) || 0)
const height = imagesMetadata[11]
const width = imagesMetadata[15]
const imagesCount = (imagesByteArray.length - 16) / (width * height)
const images: Image[] = Array(Math.floor(imagesCount)).fill(0)
for (let i = 0; i < imagesCount; i++) {
images[i] = {
label: labelsByteArray[i + 8],
bitmap: Array(height).fill(Array(width).fill(0))
}
for (let j = 0; j < width; j++) {
for (let k = 0; k < height; k++) {
images[i].bitmap[j][k] = imagesByteArray[i * width * height + j * height + k + 16]
}
}
}
return images
}