ERC721 的元資料擴充（metadata extension）

一個 ERC721 的標準中，我們可以發現它定義了每個 NFT 對應到獨一無二的 tokenId，但卻沒有把每個 NFT 的實際資料儲存在合約中，這樣我們怎麼知道花了大錢買的 NFT 就是一張 JPG 圖片呢？

ERC721 metadata extension

interface ERC721Metadata /* is ERC721 */ {
    /// 回傳本 NFT 系列的名稱
    function name() external view returns (string _name);

    /// 回傳本 NFT 系列的簡稱
    function symbol() external view returns (string _symbol);

    /// 回傳 URI (Uniform Resource Identifier)
    /// URI 可能指向一個代表了 ERC721 元資料 JSON 綱要的檔案
    function tokenURI(uint256 _tokenId) external view returns (string);
}

ERC721 metadata JSON schema

就是一個簡單的 JSON 格式，紀錄了 NFT 的名稱、簡介、與圖片。

{
    "title": "Asset Metadata",
    "type": "object",
    "properties": {
        "name": {
            "type": "string",
            "description": "Identifies the asset to which this NFT represents"
        },
        "description": {
            "type": "string",
            "description": "Describes the asset to which this NFT represents"
        },
        "image": {
            "type": "string",
            "description": "A URI pointing to a resource with mime type image/* representing the asset to which this NFT represents. Consider making any images at a width between 320 and 1080 pixels and aspect ratio between 1.91:1 and 4:5 inclusive."
        }
    }
}

以 Proof of Stake: Pages 為例

OpenSea 頁面： https://opensea.io/collection/proof-of-stake-pages 在 etherscan 上的頁面： https://etherscan.io/address/0x5bf5bcc5362f88721167c1068b58c60cad075aac

這是一本由 Vitalik 寫的書，價格是自由樂捐的，他會以 NFT 的形式紀錄了捐款的證書。

NFT 圖片

比如，這就是我捐款的證明：

NFT URI

而我的 tokenId 為 59383，我們可以去 etherscan 上面用 ERC721 的介面來查詢 URI 的資訊：

此時可以看到他是以 JSON base64 編碼的方式儲存在上面：

{"signed_to":"hydai.eth", "external_url":"https://proofofstake.gitcoin.co/", "timestamp":"1662830690", "pledge":"50000000000000000", "message":"Thank you for supporting public goods, and enjoy the book!", "image": "data:image/svg+xml;base64,<svg xmlns="http://www.w3.org/2000/svg" width="606.2" height="819.4" viewBox="0 0 606.2 819.4"><defs><style>.a{fill:#fff;}.b{fill:none;stroke:#d9c8db;stroke-miterlimit:10;stroke-width:2px;}.c,.d,.e,.f,.g,.h,.i,.j,.k,.l,.m,.n,.o{isolation:isolate;}.c,.d,.e,.f,.g,.i,.j,.k{font-size:55px;}.c,.e{fill:#e96b5d;}.c,.d,.e,.f,.g,.k{font-family:LustDisplay-Didone, Lust Didone;}.d,.f{fill:#9b4a8d;}.e{letter-spacing:0.02em;}.f{letter-spacing:0.02em;}.g{fill:#9b4a8c;}.h{font-size:45px;fill:#0cb6ea;font-family:Lust-Italic, Lust;font-style:italic;}.i,.k{fill:#50ae58;}.i,.j{font-family:Lust-Regular, Lust;letter-spacing:0.05em;}.j{fill:#ef8916;}.l,.m{font-size:29.99px;}.l,.n{font-family:Arial-BoldMT, Arial;font-weight:700;}.m,.o{font-family:ArialMT, Arial; margin-left: auto; margin-right: auto; width: 40%;}.n{font-size:20px;}.o{font-size:18px;}</style></defs><rect class="a" width="606.2" height="819.4"/><text class="n"><tspan class="n" text-anchor="middle" x="50%" y="42%">hydai.eth</tspan></text><text transform="translate(75 352.85)" font-size="18" font-family="ArialMT, Arial"><tspan text-anchor="middle" x="37.5%" y="200">1662830690</tspan><tspan text-anchor="middle" x="37.5%" y="260">50000000000000000 (wei)</tspan><tspan text-anchor="middle" x="37.5%" y="320">0x5bf5bcc5362f88721167c1068b58c60cad075aac</tspan><tspan text-anchor="middle" x="37.5%" y="120">"Thank you for supporting public goods, and enjoy the book!"</tspan><tspan text-anchor="middle" x="37.5%" y="220">mint timestamp</tspan><tspan text-anchor="middle" x="37.5%" y="340">contract</tspan><tspan text-anchor="middle" x="37.5%" y="280">value</tspan><tspan text-anchor="middle" x="37.5%" y="140"></tspan></text><rect class="b" x="21.9" y="169.5" width="562.4" height="562.4"/><g style="isolation:isolate"><path d="M46.66,98.93v-.28h4.89V60.71H46.66v-.28H65.91c12,0,18.42,3.19,18.42,11.17,0,9.4-11.77,11.27-19.85,11.27h-1.6V98.65h5.83v.28ZM62.88,82.6h1.6c5.83,0,7.75-3.47,7.75-11s-1.92-10.89-7.75-10.89h-1.6Z" style="fill:#e96b5d"/></g><g style="isolation:isolate"><path d="M135,91.84c0,5.16-2.26,7.53-9.21,7.53-6.74,0-9.43-2.28-11.55-8.63C113,87,112.44,79.52,107.52,79.52h-1.6V98.65h5.28v.28H89.7v-.28h4.89V60.71H89.7v-.28H109c5.66,0,18.47.22,18.47,9.46,0,7.54-10.77,9.27-17.32,9.54v.09c10.75,0,13.94,3.52,16.58,9.15,3.33,7.12,4.13,8.17,5.53,8.17,2.2,0,2.47-3.35,2.47-5Zm-29-12.6h1.6c5.44,0,7.81-2.86,7.81-9.35,0-5.11-1.82-9.18-7.79-9.18h-1.62Z" style="fill:#9b4a8d"/></g><g style="isolation:isolate"><path d="M178.65,79.68c0,12.54-8.85,19.69-19.71,19.69s-19.72-7.15-19.72-19.69S148.07,60,158.94,60,178.65,67.14,178.65,79.68Zm-11.8,0c0-8.41-.52-19.41-7.91-19.41S151,71.27,151,79.68s.52,19.41,7.92,19.41S166.85,88.1,166.85,79.68Z" style="fill:#e96b5d"/></g><g style="isolation:isolate"><path d="M226.68,79.68c0,12.54-8.9,19.69-19.83,19.69S187,92.22,187,79.68,195.92,60,206.85,60,226.68,67.14,226.68,79.68Zm-11.87,0c0-8.41-.52-19.41-8-19.41s-8,11-8,19.41.52,19.41,8,19.41S214.81,88.1,214.81,79.68Z" style="fill:#9b4a8d"/></g><g style="isolation:isolate"><path d="M236.69,98.93v-.28h4.89V60.71h-4.89v-.28h33.93L272,73.69h-.27l-.11-1c-.8-7.56-6.82-12-14.3-12h-4.4V79.13h.61c6.18,0,10.2-2.58,10.5-7.72l.05-1h.28l-.93,17.77h-.28l.05-1c.28-5.12-3.49-7.81-9.67-7.81h-.61V98.65h5.83v.28Z" style="fill:#9b4a8c"/></g><g style="isolation:isolate"><path d="M307.71,87.38c0,7.47-6.75,14.17-14.76,14.17-6.43,0-10.89-4.27-10.89-10.21,0-7.7,6.62-14.18,14.72-14.18C303.26,77.16,307.71,81.44,307.71,87.38Zm-8.23-4.64c0-2.65-.5-5.22-2.75-5.22-5,0-6.43,13.86-6.43,18.54,0,2.66.49,5.13,2.7,5.13C298,101.19,299.48,88.05,299.48,82.74Z" style="fill:#0cb6ea"/></g><g style="isolation:isolate"><path d="M300.13,105.46a4.61,4.61,0,0,1,4.68-4.77,3.93,3.93,0,0,1,4.09,4.18,3.26,3.26,0,0,0-2.7,3.29c0,1.08.45,1.93,1.71,1.93,2.12,0,4-2.34,4-5.76,0-2.07-.67-4.32-4-5.49l3.37-22H307.6l0-.36h3.65c.31-6.7,2.52-11.88,9.18-11.88,4.5,0,6.57,2.48,6.57,5.27a4.75,4.75,0,0,1-4.82,5c-2.2,0-4-1.44-4-4.27a3.09,3.09,0,0,0,2.88-3.2c0-1.35-.58-2.29-2.07-2.29-5.31,0-6.84,11.38,1.44,11.38h3.2l0,.36h-4.27L316,98.75c-.86,5.4-3.47,12-9.77,12C302.29,110.72,300.13,108.2,300.13,105.46Z" style="fill:#0cb6ea"/></g><g style="isolation:isolate"><path d="M345.85,98.1l-4.07,1.16-.88-16h.44c.88,6.44,4.45,15.62,14.35,15.62,5,0,9-1.76,9-5.83,0-9.24-24-8.41-24-21.72C340.68,64,347.77,60,356.57,60a39.37,39.37,0,0,1,8.75,1.26l4.18-1.16.71,13.53h-.44c-.88-6.21-4.34-13.19-13.2-13.19-4.4,0-7.42,2.08-7.42,5.66,0,8.41,24,7.09,24,20.79,0,7.75-8.13,12.48-17.43,12.48A41.65,41.65,0,0,1,345.85,98.1Z" style="fill:#50ae58"/><path d="M384.62,98.93v-.44c5.72,0,6.27-3,6.27-9.46V60.88c-8.91,0-12.87,5.33-13.8,13.63h-.44l1.48-14.07H415l1.48,14.07H416c-.93-8.3-4.89-13.63-13.8-13.63V89c0,6.44.55,9.46,6.27,9.46v.44Z" style="fill:#50ae58"/></g><g style="isolation:isolate"><path d="M455.54,88.43c3.46,7.2,5.11,10.06,9.07,10.06v.44H442.18v-.44c5.22,0,4.18-4.18,1.48-9.95l-1.39-3H429.18c-4,8.38-2.59,12.92,3.43,12.92v.44H417.1v-.44c4,0,7.42-4.67,11.71-13.36l12.71-25.79ZM429.45,85H442l-6.11-13.08Z" style="fill:#ef8916"/><path d="M504.71,87.66c4.29,9.51,5.5,10.39,8.14,10.11v.45a36.94,36.94,0,0,1-8.75,1.26c-6.76,0-9.4-2.58-11.43-8.74-1.76-5.34-3.25-11.44-6.77-11.44a4.07,4.07,0,0,0-1.81.46V89c0,6.44.49,9.46,4.56,9.46v.44H467.26v-.44c5.5,0,5.5-3,5.5-9.46V70.33c0-6.65,0-9.46-5.5-9.46v-.43h21.39v.43c-4.07,0-4.56,3-4.56,9.46V79.1l7-7.67c2.36-2.53,5.39-6.16,5.39-8.41,0-1.49-1-2.15-3.63-2.15v-.43h16.66v.43c-7,0-14.68,7.32-18,10.95l-6.48,7a18,18,0,0,1,8.24-2c5.56,0,8.19,3.3,11.44,10.84Z" style="fill:#ef8916"/></g><g style="isolation:isolate"><path d="M552.2,73.69h-.28l-.11-1c-.8-7.56-6.82-12-14.3-12H532V79.13h.61c6.18,0,10.2-2.58,10.5-7.72l.06-1h.27l-.93,17.77h-.28l.06-1c.27-5.12-3.5-7.81-9.68-7.81H532V92c0,5.33.61,6.7,4.4,6.7,9.87,0,16-6.15,17.35-15l.2-1.24h.27l-2.64,16.5h-35.8v-.28h4.89V60.71h-4.89v-.27h35Z" style="fill:#50ae58"/></g><text class="l" transform="translate(235.15 265)">vitalik.eth</text> <text class="m" transform="translate(263.48 295)">signer</text> <text class="m" transform="translate(245.64 373)">recipient</text></svg>"}

在使用 base64 格式解碼後可以得到以下資料：

{
   "signed_to":"hydai.eth",
   "external_url":"https://proofofstake.gitcoin.co/",
   "timestamp":"1662830690",
   "pledge":"50000000000000000",
   "message":"Thank you for supporting public goods, and enjoy the book!",
   "image":"data:image/svg+xml;base64,<svg xmlns="http://www.w3.org/2000/svg" width="606.2" height="819.4" viewBox="0 0 606.2 819.4"><defs><style>.a{fill:#fff;}.b{fill:none;stroke:#d9c8db;stroke-miterlimit:10;stroke-width:2px;}.c,.d,.e,.f,.g,.h,.i,.j,.k,.l,.m,.n,.o{isolation:isolate;}.c,.d,.e,.f,.g,.i,.j,.k{font-size:55px;}.c,.e{fill:#e96b5d;}.c,.d,.e,.f,.g,.k{font-family:LustDisplay-Didone, Lust Didone;}.d,.f{fill:#9b4a8d;}.e{letter-spacing:0.02em;}.f{letter-spacing:0.02em;}.g{fill:#9b4a8c;}.h{font-size:45px;fill:#0cb6ea;font-family:Lust-Italic, Lust;font-style:italic;}.i,.k{fill:#50ae58;}.i,.j{font-family:Lust-Regular, Lust;letter-spacing:0.05em;}.j{fill:#ef8916;}.l,.m{font-size:29.99px;}.l,.n{font-family:Arial-BoldMT, Arial;font-weight:700;}.m,.o{font-family:ArialMT, Arial; margin-left: auto; margin-right: auto; width: 40%;}.n{font-size:20px;}.o{font-size:18px;}</style></defs><rect class="a" width="606.2" height="819.4"/><text class="n"><tspan class="n" text-anchor="middle" x="50%" y="42%">hydai.eth</tspan></text><text transform="translate(75 352.85)" font-size="18" font-family="ArialMT, Arial"><tspan text-anchor="middle" x="37.5%" y="200">1662830690</tspan><tspan text-anchor="middle" x="37.5%" y="260">50000000000000000 (wei)</tspan><tspan text-anchor="middle" x="37.5%" y="320">0x5bf5bcc5362f88721167c1068b58c60cad075aac</tspan><tspan text-anchor="middle" x="37.5%" y="120">"Thank you for supporting public goods, and enjoy the book!"</tspan><tspan text-anchor="middle" x="37.5%" y="220">mint timestamp</tspan><tspan text-anchor="middle" x="37.5%" y="340">contract</tspan><tspan text-anchor="middle" x="37.5%" y="280">value</tspan><tspan text-anchor="middle" x="37.5%" y="140"></tspan></text><rect class="b" x="21.9" y="169.5" width="562.4" height="562.4"/><g style="isolation:isolate"><path 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}

結語

通過 URI JSON Schema 我們可以把 NFT 的詳細資訊給記錄在合約中。然而，Proof-of-Stake: Pages 的圖片非常簡單，因此可以使用 SVG 圖片格式直接編碼在 URI 內。

但，如果 NFT 代表的是一部 4K 影片、一張 8K 圖片等大型檔案，由於儲存成本會變得過高，因此會改用連結到該檔案的方式取代。