可接受的答案不考虑缓存图像以提高性能。您无需每次请求图像时都调整大小和覆盖图像。以下方法将调整大小后的图像保存到“缓存”文件夹中，因此连续的调用会从缓存中返回该图像。该方法包含在一个助手（不是块）中，因此您可以从任何喜欢的模板中调用它：
应用程序/代码/供应商/命名空间/Helper/Image.php
<?php
namespace Vendor\Namespace\Helper;
use Magento\Framework\App\Filesystem\DirectoryList;
class Image extends \Magento\Framework\App\Helper\AbstractHelper
{
/**
* Custom directory relative to the "media" folder
*/
const DIRECTORY = 'custom_module/posts';
/**
* @var \Magento\Framework\Filesystem\Directory\WriteInterface
*/
protected $_mediaDirectory;
/**
* @var \Magento\Framework\Image\Factory
*/
protected $_imageFactory;
/**
* Store manager
*
* @var \Magento\Store\Model\StoreManagerInterface
*/
protected $_storeManager;
/**
* @param \Magento\Framework\App\Helper\Context $context
* @param \Magento\Framework\Filesystem $filesystem
* @param \Magento\Framework\Image\Factory $imageFactory
* @param \Magento\Store\Model\StoreManagerInterface $storeManager
*/
public function __construct(
\Magento\Framework\App\Helper\Context $context,
\Magento\Framework\Filesystem $filesystem,
\Magento\Framework\Image\AdapterFactory $imageFactory,
\Magento\Store\Model\StoreManagerInterface $storeManager
) {
$this->_mediaDirectory = $filesystem->getDirectoryWrite(DirectoryList::MEDIA);
$this->_imageFactory = $imageFactory;
$this->_storeManager = $storeManager;
parent::__construct($context);
}
/**
* First check this file on FS
*
* @param string $filename
* @return bool
*/
protected function _fileExists($filename)
{
if ($this->_mediaDirectory->isFile($filename)) {
return true;
}
return false;
}
/**
* Resize image
* @return string
*/
public function resize($image, $width = null, $height = null)
{
$mediaFolder = self::DIRECTORY;
$path = $mediaFolder . '/cache';
if ($width !== null) {
$path .= '/' . $width . 'x';
if ($height !== null) {
$path .= $height ;
}
}
$absolutePath = $this->_mediaDirectory->getAbsolutePath($mediaFolder) . $image;
$imageResized = $this->_mediaDirectory->getAbsolutePath($path) . $image;
if (!$this->_fileExists($path . $image)) {
$imageFactory = $this->_imageFactory->create();
$imageFactory->open($absolutePath);
$imageFactory->constrainOnly(true);
$imageFactory->keepTransparency(true);
$imageFactory->keepFrame(true);
$imageFactory->keepAspectRatio(true);
$imageFactory->resize($width, $height);
$imageFactory->save($imageResized);
}
return $this->_storeManager->getStore()->getBaseUrl(\Magento\Framework\UrlInterface::URL_TYPE_MEDIA) . $path . $image;
}
}
现在，您可以从任何.phtml模板调用如下方法：
<!-- Get a reference to the Image helper -->
<?php $image = $this->helper('Vendor\Namespace\Helper\Image'); ?>
.
.
.
<!-- Resize the image by specifying width only -->
<img src="<?php echo $image->resize('/my-picture.jpg', 1200); ?>">
<!-- Resize the image by specifying width and height -->
<img src="<?php echo $image->resize('/my-picture.jpg', 640, 480); ?>">