在以太坊区块链上创建一个动态 SVG NFT_动态svg链

  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(
      "<svg width='500' height='500' xmlns='http://www.w3.org/2000/svg'>",
      "<defs>",
      "<linearGradient id='bg' x1='0%' y1='0%' x2='100%' y2='100%'>",
      gradientColors,
      "</linearGradient>",
      "</defs>",
      "<rect width='100%' height='100%' fill='url(#bg)'>",
      "<animate attributeName='x' from='-500' to='500' dur='", animationDuration, "s' repeatCount='indefinite'/>",
      "</rect>",
      _generateCircles(seed),
      "</svg>"
    ));
  }
 
  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(
      "<stop offset='0%' stop-color='", color1, "'>",
      "<animate attributeName='stop-color' values='", color1, ";", color2, ";", color3, ";", color1, "' dur='10s' repeatCount='indefinite'/>",
      "</stop>",
      "<stop offset='100%' stop-color='", color2, "'>",
      "<animate attributeName='stop-color' values='", color2, ";", color3, ";", color1, ";", color2, "' dur='10s' repeatCount='indefinite'/>",
      "</stop>"
    ));
  }
 
  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(
      "<circle cx='", Strings.toString(cx),
      "' cy='", Strings.toString(cy),
      "' r='", Strings.toString(r),
      "' fill='rgba(255,255,255,0.5)' stroke='white'>",
      "<animate attributeName='r' values='", Strings.toString(r), ";", Strings.toString(r + 10), ";", Strings.toString(r),
      "' dur='", animationDuration, "s' repeatCount='indefinite'/>",
      "</circle>"
    ));
  }
}

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。