通过Solidity编写的合约基于 ERC721 标准，并使用 OpenZeppelin 库来实现基本功能。

导入库

import '@openzeppelin/contracts/token/ERC721/ERC721.sol'; import '@openzeppelin/contracts/token/ERC721/extensions/ERC721URIStorage.sol'; import '@openzeppelin/contracts/utils/Counters.sol'; import 'base64-sol/base64.sol'; import "@openzeppelin/contracts/utils/Strings.sol"; 

这些导入语句包含了 ERC721 标准合约、扩展功能、计数器工具、Base64 编码工具和字符串工具。

合约定义 

contract DynamicSvgToken is ERC721URIStorage {   using Counters for Counters.Counter;   Counters.Counter private _tokenCounter;    string[] palette;    constructor() ERC721('Dynamic SVG Token', 'DST') {     palette = ["blue", "red", "maroon", "black", "yellow", "orange", "purple", "gold", "lawngreen", "lightblue", "olive"];   }    function mint() external {     _tokenCounter.increment();     uint256 newTokenId = _tokenCounter.current();     _safeMint(msg.sender, newTokenId);     _setTokenURI(newTokenId, _constructTokenURI(newTokenId));   }    function _constructTokenURI(uint256 tokenId) internal view returns (string memory) {     string memory svg = _constructSVG(tokenId);     string memory json = Base64.encode(bytes(string(abi.encodePacked(       '{"name": "',        name(),       '", "description": "A dynamic SVG NFT with animated gradient background", "image": "data:image/svg+xml;base64,',        Base64.encode(bytes(svg)),        '"}'     ))));     return string(abi.encodePacked('data:application/json;base64,', json));   }    function _constructSVG(uint256 tokenId) internal view returns (string memory) {     uint seed = uint(keccak256(abi.encodePacked(block.timestamp, tokenId)));          string memory gradientColors = _getRandomGradientColors(seed);     string memory animationDuration = Strings.toString(5 + (seed % 10)); // 5-14 seconds      return string(abi.encodePacked(       ""     ));   }    function _getRandomGradientColors(uint seed) internal view returns (string memory) {     string memory color1 = palette[seed % palette.length];     string memory color2 = palette[(seed / palette.length) % palette.length];     string memory color3 = palette[(seed / (palette.length * palette.length)) % palette.length];      return string(abi.encodePacked(       "",       "",       "",       "",       "",       ""     ));   }    function _generateCircles(uint seed) internal pure returns (string memory) {     string memory circles;     for (uint i = 0; i < 3; i++) {       uint circleSeed = uint(keccak256(abi.encodePacked(seed, i)));       circles = string(abi.encodePacked(circles, _generateCircle(circleSeed, i)));     }     return circles;   }    function _generateCircle(uint seed, uint index) internal pure returns (string memory) {     uint cx = seed % 400 + 50;     uint cy = (seed / 1000) % 400 + 50;     uint r = (seed / 1000000) % 50 + 10;     string memory animationDuration = Strings.toString(3 + index * 2); // 3, 5, or 7 seconds      return string(abi.encodePacked(       "",       "",       ""     ));   } }

定义了一个名为 DynamicSvgToken 的合约，继承自ERC721URIStorage，并使用 Counters 库来管理代币 ID。palette 是一个包含颜色的字符串数组。构造函数初始化合约，设置代币名称为 "Dynamic SVG Token"，符号为 "DST"，并填充 palette 数组。mint 函数用于铸造新的代币，增加计数器并安全地将代币铸造给调用者，同时设置代币的 URI。_constructTokenURI 函数构建代币的 JSON 元数据，并将其编码为 Base64。_getRandomGradientColors 函数根据种子生成三个随机颜色，并创建渐变动画。_generateCircles 函数生成多个圆形元素，每个圆形都有不同的种子和动画。_generateCircle 函数生成一个带有动画的圆形元素。

总体来说，这段代码实现了一个动态生成 SVG 图像的 NFT，每个图像都有随机的渐变背景和动画圆形。