将imagemagick命令转换为PHP

To lean against this question:

Imagick: Convert bash command into php script

I have a command that does exactly what I want to:

convert input.jpg -alpha set -bordercolor "rgb(255,255,255)" 
  -border 1 -fill none -fuzz 5% -draw "color 0,0 floodfill" -shave 1x1 out.png

So I tried to do the same thing in PHP Imagick.

$backgroundColor = $image->getImagePixelColor(0, 0);

$image->setImageAlphaChannel(\Imagick::ALPHACHANNEL_SET);
$image->borderImage($backgroundColor->getColorAsString(), 1, 1);
$image->floodFillPaintImage(
     'transparent',
     $fuzz * \Imagick::getQuantum(),
     $backgroundColor->getColorAsString(),
     0, 0, 
     false);
$image->shaveImage(1, 1);

I need this working in PHP not as a shell_exec() command.

But the result of my PHP code is just a black image.

To test I use the image from phpimagick.com

image: https://phpimagick.com/imageOriginal/Tutorial/backgroundMasking

It is not necessary, that the inside of the chair is transparent too. I just need the background going away.

Some of you have any idea?

Thank you for your reply.