I try to implement multi crop with raw. cause, traditional ways extract then save to buffer is to slow . for my task, an image it takes 700ms. i want to cutdown extract call with manipulate raw data. so it can speed up 10x - 20x. my problem in extract frame into sequential block size. lets say 16x16 from left top to right bottom.

const sharp = require('sharp');

const benchmark = () => {
    return new Promise((resolve) => {
        const currentTime = Date.now();
        resolve(currentTime)
    })
};

const encode = async (absolutePathFile) => {
    const start_time = await benchmark();

    const image = await sharp(absolutePathFile);
    const { data, info } = await image.ensureAlpha(1).raw().toBuffer({ resolveWithObject: true });
    const { width, height, channels } = info;
    const colors = new Uint8ClampedArray(data.buffer);
    const pixels = [];
    const frame = [];
    const frameBlocks = [];

    // Convert colors to RGBA pixel
    for (let i=0; i < colors.length; i += channels) {
        const pixel = [];
        for (let j=i; j < i + channels; j++) {
            pixel.push(colors[j])
        };
        pixels.push(pixel)
    }

    // Convert pixels to frame
    let index = 0;
    for (let i=0; i < width; i++) {
        frame[i] = [];

        for (let j=0; j < height; j++) {
            frame[i][j] = pixels[index];
            index += 1;
        }
    };

    // Crop frame to piece of block size from left top to right bottom.
    const wBlockSize = 16;
    const hBlockSize = 16;
    const wBlockLength = Math.floor(width/wBlockSize);
    const hBlockLength = Math.floor(height/hBlockSize);

    for (let i=0; i < wBlockLength; i++) { 
        for (let j=0; j < hBlockLength; j++) {
            const block = [];
            for (let k=i; k < i+wBlockSize; k++) {
                for (let l=j; l+hBlockSize; l++) {
                    block.push(frame[k][l])
                }
            };

            frameBlocks.push(block)
        }
    };

    const end_time = await benchmark();
    const finish_time = end_time - start_time;
    console.log(finish_time);
   
    console.log(frameBlocks.length)
};

encode(`${__dirname}/public/image.jpg`)