vue前端通过图片链接下载后has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

当在Vue前端中通过图片链接下载图片时，如果出现"has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource"的错误提示，这是由于浏览器的同源策略所导致的。

同源策略是一种安全机制，它限制了从一个源加载的文档或脚本如何与来自另一个源的资源进行交互。在浏览器中，如果请求的资源与当前页面的域名、协议或端口不一致，就会触发跨域请求，而跨域请求默认是被浏览器禁止的。

解决这个问题的方法有几种：
1. 服务器端设置响应头：在服务器端设置响应头，添加"Access-Control-Allow-Origin"字段，并设置为"*"或指定允许跨域的域名。例如，在Node.js中可以使用`cors`模块来实现跨域访问控制。
2. 使用代理：在Vue项目的配置文件（vue.config.js）中配置代理，将请求转发到同源的接口上。这样可以绕过浏览器的同源策略限制。
3. 将图片转为Base64编码：将图片转为Base64编码后，直接在前端使用编码后的字符串作为图片源，这样就不会触发跨域请求。

相关问题

vue blocked by CORS policy: No Access-Control-Allow-Origin header is present on the requested resource.

跨域资源共享（CORS）是一种机制，它使用额外的HTTP头来告诉浏览器让运行在一个origin（域）上的Web应用被准许访问来自不同源服务器上的指定的资源。如果一个资源的访问没有得到允许，那么就会出现“blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.”的错误提示。解决这个问题的方法有以下几种：

1.在服务端设置Access-Control-Allow-Origin头部信息，允许跨域访问。例如，在Node.js中，可以使用cors模块来设置：

const express = require('express');
const cors = require('cors');
const app = express();
app.use(cors());

2.使用代理服务器，将请求转发到目标服务器。例如，在vue.config.js中配置代理：

module.exports = {
  devServer: {
    proxy: {
      '/api': {
        target: 'http://localhost:3000',
        changeOrigin: true,
        pathRewrite: {
          '^/api': ''
        }
      }
    }
  }
}

3.在前端使用JSONP或者WebSocket等技术进行跨域请求。

Vue has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

The error message you are seeing indicates a Cross-Origin Resource Sharing (CORS) issue. CORS is a browser security feature that prohibits web pages from making requests to a different domain than the one that served the page.

To resolve this issue, you have a few options:

1. Configure the server: You need to add the appropriate response headers to your server's responses to allow cross-origin requests. Specifically, you need to include the "Access-Control-Allow-Origin" header with the value of the requesting domain.

2. Use a proxy server: If you don't have control over the server's configuration, you can set up a proxy server that forwards requests from your domain to the target server. By doing this, the same-origin policy will be satisfied, and CORS won't be an issue.

3. Use a JSONP request: If the server supports JSONP (JSON with Padding), you can use it as an alternative. JSONP is a technique that allows making cross-origin requests by dynamically adding a ```<script>``` tag to the page.

Choose the appropriate solution based on your specific situation and server setup.