1、为Magento\Quote\Api\Data\CartItemInterface扩展属性

etc/extension_attributes.xml

内容：

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Api/etc/extension_attributes.xsd">
    <extension_attributes for="Magento\Quote\Api\Data\CartItemInterface">
        <attribute code="image_url" type="string" />
    </extension_attributes>
</config>

2、声明观察者修改读取item后添加item产品图

etc/events.xml

内容：

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
    <event name="sales_quote_load_after">
        <observer name="Aiweline_SimplePageShop_sales_quote_load_after" instance="Aiweline\SimplePageShop\Observer\CartItemAddImage" />
    </event>
</config>

3、创建观察者CartItemAddImage

Aiweline\SimplePageShop\Observer\CartItemAddImage

内容：

<?php
/**
 * @Author       秋枫雁飞
 * @Email        aiweline@qq.com/1714255949@qq.com
 * @Desc         文件由Aiweline(秋枫雁飞)编写，若有升级需要
 *               建议不要随意修改文件源码。
 **/
namespace Aiweline\SimplePageShop\Observer;
use Magento\Framework\Event\ObserverInterface;
use Magento\Catalog\Api\ProductRepositoryInterfaceFactory as ProductRepository;
use Magento\Catalog\Helper\ImageFactory as ProductImageHelper;
use Magento\Framework\ObjectManagerInterface;
use Magento\Store\Model\StoreManagerInterface as StoreManager;
use Magento\Store\Model\App\Emulation as AppEmulation;
use Magento\Quote\Api\Data\CartItemExtensionFactory;
class CartItemAddImage implements ObserverInterface
{
    /**
     * @var ObjectManagerInterface
     */
    protected ObjectManagerInterface $_objectManager;
    /**
     * @var ProductRepository
     */
    protected ProductRepository $productRepository;
    /**
     * @var \Magento\Catalog\Helper\ImageFactory
     */
    protected ProductImageHelper $productImageHelper;
    /**
     * @var \Magento\Store\Model\StoreManagerInterface
     */
    protected StoreManager $storeManager;
    /**
     * @var \Magento\Store\Model\App\Emulation
     */
    protected AppEmulation $appEmulation;
    /**
     * @var CartItemExtensionFactory
     */
    protected CartItemExtensionFactory $extensionFactory;
    /**
     * @param \Magento\Framework\ObjectManagerInterface $objectManager
     * @param ProductRepository $productRepository
     * @param \Magento\Catalog\Helper\ImageFactory
     * @param \Magento\Store\Model\StoreManagerInterface
     * @param \Magento\Store\Model\App\Emulation
     * @param CartItemExtensionFactory $extensionFactory
     */
    public function __construct(
        \Magento\Framework\ObjectManagerInterface $objectManager,
        ProductRepository $productRepository,
        ProductImageHelper $productImageHelper,
        StoreManager $storeManager,
        AppEmulation $appEmulation,
        CartItemExtensionFactory $extensionFactory
    )
    {
        $this->_objectManager = $objectManager;
        $this->productRepository = $productRepository;
        $this->productImageHelper = $productImageHelper;
        $this->storeManager = $storeManager;
        $this->appEmulation = $appEmulation;
        $this->extensionFactory = $extensionFactory;
    }
    public function execute(\Magento\Framework\Event\Observer $observer, string $imageType = NULL)
    {
        $quote = $observer->getQuote();
        /**
         * 添加items的属性到扩展属性
         */
        foreach ($quote->getAllItems() as $quoteItem) {
            $product = $this->productRepository->create()->getById($quoteItem->getProductId());
            $itemExtAttr = $quoteItem->getExtensionAttributes();
            if ($itemExtAttr === null) {
                $itemExtAttr = $this->extensionFactory->create();
            }
            $imageurl = $this->productImageHelper->create()->init($product, 'product_thumbnail_image')->setImageFile($product->getThumbnail())->getUrl();
            $itemExtAttr->setImageUrl($imageurl);
            $quoteItem->setExtensionAttributes($itemExtAttr);
        }
        return;
    }
    /**
     * 提供完整缓存图像url的帮助函数
     * @param \Magento\Catalog\Model\Product
     * @return string
     */
    protected function getImageUrl($product, string $imageType = NULL)
    {
        $storeId = $this->storeManager->getStore()->getId();
        $this->appEmulation->startEnvironmentEmulation($storeId, \Magento\Framework\App\Area::AREA_FRONTEND, true);
        $imageUrl = $this->productImageHelper->create()->init($product, $imageType)->getUrl();
        $this->appEmulation->stopEnvironmentEmulation();
        return $imageUrl;
    }
}

安装代码：

bin/magento setup:upgrade
bin/magento c:c

完毕！