function setBlack(pixel) {
     pixel.setRed(0);
     pixel.setGreen(0);
     pixel.setBlue(0);
     return pixel;
}

function pixelOnEdgeDifferentThicknesses (pixel, image, vWidth, hWidth) {
     var x = pixel.getX();
     var y = pixel.getY();
     if (x < vWidth) return true;
     if (y < hWidth) return true;
     if (x >= image.getWidth() - vWidth) return true;
     if (y >= image.getHeight() - hWidth) return true;
     return false;
}
var image = new SimpleImage("usain.jpg");
for (var pixel of image.values()) {
     if (pixelOnEdgeDifferentThicknesses (pixel, image, 10, 40)) {      
          pixel = setBlack(pixel);
     }
}

print(image);