Unexpected image rotation in decoding-encoding process with jpeg-js library

Question

I'm using jpeg-js library to decode an image, apply my own greyscale filter, and encode it back. But unfortunately every vertical picture I process for some reason is rotated and saved horizontally (while horizontal images preserve its correct rotation and are totally ok). Here's my code:

function greyscale(width, height, data, bytesPerPixel, imageName) {
    const bwPixelData = Buffer.alloc(data.length)

    for (let vrt = 0; vrt < height; vrt++) {
        for (let hrz = 0; hrz < width; hrz++) {
            const offset = (vrt * width + hrz) * bytesPerPixel
            
            const red = data[offset]
            const green = data[offset + 1]
            const blue = data[offset + 2]
            
            const bwPixel = Math.round((red + green + blue) / 3.0)
            
            bwPixelData[offset] = bwPixel
            bwPixelData[offset + 1] = bwPixel
            bwPixelData[offset + 2] = bwPixel
            
        }
    }

    const filteredImageName = encodeImage(bwPixelData, width, height, imageName)
    return filteredImageName

}
exports.decodeImage = function(name, path) {
    if (name.match(/.*\.jpe?g/i)){
        const jpegData =  fs.readFileSync(path)
        return jpeg.decode(jpegData)
    } else {
        throw new Error('Unsupported Media Type')
    }
}


exports.encodeImage = function(data, width, height, imageName) {
    
    const filteredImageName = `outfile-${imageName}`
    
    const rawImageData = {
        data: data,
        width: width,
        height: height,
    }

    
    const jpegImageData = jpeg.encode(rawImageData, 50)

    try {
        fs.writeFileSync(`${outputPath}/${filteredImageName}`, jpegImageData.data);
        console.log('File written successfully');
    } catch (error) {
        console.error('Error writing file:', error);
    }

    return filteredImageName
} 

At first I thought that the problem might be hidden in the greyscale function and how I process pixels. So I tried to decode, encode, and save back an original, unfiltered, vertical photo, which had lead to the same result: unexpected rotation.

Have you ever faced a problem like this and does anyone know how to fix it? It's also important to me to use a pure js implementation instead of libraries like Sharp