Extract image inscription of tx 4be3a833ee83b4ca7d157d60fbf7411f7528314ce90df8a844f855118bc6ca11

dinner-inscription.js

#! /usr/bin/env node

// Invoke with: bitcoin-cli getrawtransaction 4be3a833ee83b4ca7d157d60fbf7411f7528314ce90df8a844f855118bc6ca11 | ./dinner-inscription.js

const { Transaction } = require('bitcoinjs-lib');

if (process.stdin.isTTY) {
    console.error('raw tx needed, quitting...');
    process.exit(1);
}

let input = '';
process.stdin.on('data', chunk => input += chunk);
process.stdin.on('end', () => main());

function main() {
    const tx = Transaction.fromHex(Buffer.from(input, 'hex'));

    let data = Buffer.alloc(0);
    for (const input of tx.ins) {
        const script = input.script;
        let cursor = 0;
        
        const redeemSize = script[0]; // ignore 1st push
        cursor++;
        cursor += redeemSize;

        while (cursor < script.length) {
            const opcode = script[cursor];
            cursor++;

            if (opcode === 0x4c) { // redeem script
                break;
            } else if (opcode === 0x4d) {
                const size = script.readUIntLE(cursor, 2);
                cursor += 2;
                const chunk = script.subarray(cursor, cursor + size);
                data = Buffer.concat([data, chunk]);
                cursor += size;
            } else {
                console.error(`unexpected opcode: ${opcode.toString(16)}`);
                process.exit(1);
            }
        }
    }

    const start = Buffer.from('/9j', 'utf8');
    const end = Buffer.from('//Z', 'utf8');
    const img = data.subarray(data.indexOf(start), data.indexOf(end) + end.length).toString('utf8');
    console.log(img.replace(/\0+/g, '\n'));
}