Autocrop not cropping surrounding black area

Large Black borders should have cropped out. I have adjusted the tolerance and have see no change in results. They are simply not getting cropped.

Latest Node and Jimp on a Raspberry Pi

   Jimp.read( "./scanimage.jpg", (err, img) => {
        if (err) throw err;
        let clean = img
        .scale(0.5)
        .quality(50)
        .autocrop()
        .write('./croppedimage.jpg')