Example

function edgeExtend($virtualPixelType, $image_path)
{
    $imagick = new \Imagick(realpath($image_path));
    $imagick->setImageVirtualPixelMethod($virtualPixelType);

    $imagick->scaleImage(400, 300, true);

    $imagick->setImageBackgroundColor('red');
   
    $desiredWidth = 600;
    $originalWidth = $imagick->getImageWidth();

    $desiredHeight = 450;
    $originalHeight = $imagick->getImageHeight();

    //Make the image be the desired width.
    $imagick->sampleimage($desiredWidth, $desiredHeight);//$imagick->getImageHeight());

    // Now scale, rotate, translate (aka affine project) it
    // to be how you want
    $points = array(
        // The x scaling factor is 0.5 when the desired width is double
        // the source width
        ($originalWidth / $desiredWidth),
        0, // ($originalHeight / $desiredHeight), //0 means don't scale vertically
        0, ($originalHeight / $desiredHeight),
        // Offset the image so that it's in the centre
        ($desiredWidth - $originalWidth) / 2,
        ($desiredHeight - $originalHeight) / 2,
    );

    $imagick->distortImage(\Imagick::DISTORTION_AFFINEPROJECTION, $points, false);

    header("Content-Type: image/jpeg");
    echo $imagick->getImageBlob();

//Fyi it may be easier to think of the affine transform by 
//how it works for a rotation:
//$affineRotate = array(
//    "sx" => cos($angle),
//    "sy" => cos($angle),
//    "rx" => sin($angle),
//    "ry" => -sin($angle),
//    "tx" => 0,
//    "ty" => 0,
//);
}