function resizeAndConvertImageWebP(
    $width,
    $height,
    $density,
    $originalFilepath,
    $resizedFilepath) {
  $newWidth = $width * $density;
  $newHeight = $height * $density;

  $image = new Imagick($originalFilepath);
  $origImageDimens = $image->getImageGeometry();
  $origImgWidth = $origImageDimens['width'];
  $origImgHeight = $origImageDimens['height'];

  if($newWidth == 0) {
    $ratioOfHeight = $newHeight / $origImgHeight;
    $newWidth = $origImgWidth * $ratioOfHeight;
  }

  if($newHeight == 0) {
    $ratioOfWidth = $newWidth / $origImgWidth;
    $newHeight = $origImgHeight * $ratioOfWidth;
  }

  $widthRatios = $origImgWidth / $newWidth;
  $heightRatios = $origImgHeight / $newHeight;

  if($widthRatios <= $heightRatios) {
    $cropWidth = $origImgWidth;
    $cropHeight = $newWidth * $widthRatios;
  } else {
    $cropWidth = $newHeight * $heightRatios;
    $cropHeight = $origImgHeight;
  }

  $cropX = ($origImgWidth - $cropWidth) / 2;
  $cropY = ($origImgHeight - $cropHeight) / 2;

  $image->stripImage();
  $image->cropImage($cropWidth, $cropHeight, $cropX, $cropY);
  $image->resizeImage($newWidth, $newHeight, imagick::FILTER_LANCZOS, 0.9);
  $image->setImageFormat('webp');
  $image->setImageAlphaChannel(imagick::ALPHACHANNEL_ACTIVATE);
  $image->setBackgroundColor(new ImagickPixel('transparent'));
  $image->writeImage($resizedFilepath);
}

<?=(webps() && is_file($_SERVER['DOCUMENT_ROOT'] . str_replace('.jpg', '.webp', $arItem["DETAIL_PICTURE"]["SRC"])))?'style="background-image: url('.str_replace('.jpg', '.webp', $arItem["DETAIL_PICTURE"]["SRC"]).')':'style="background-image: url('.$arItem["DETAIL_PICTURE"]["SRC"].')'?>"

$webpsupport = (strpos($_SERVER['HTTP_ACCEPT'], 'image/webp') >= 0);
if($webpsupport) {
  $this->attemptToServeWebP($pathinfo, $matches, $width, $height, $density);
} else {
  $this->attemptToServeNormal($pathinfo, $matches, $width, $height, $density);
}