Setting the background colour of a transparent PNG when converted to JPEG

imagick_transparency.php

<?php

$image = new Imagick('kiwi.png'); // https://s13.postimg.org/hakfstg1j/kiwi.png

$image->setImageBackgroundColor(new ImagickPixel('white')); // set the background color of the image
$image->setImageAlphaChannel(Imagick::ALPHACHANNEL_BACKGROUND); // ALPHACHANNEL_BACKGROUND is undocumented and has a value of 2

// save a JPEG
$image->setImageFormat('jpeg');
$image->setImageCompression(Imagick::COMPRESSION_JPEG);
$image->setImageCompressionQuality(80);

$image->writeImage('kiwi.jpg');