node_util/index/image.js

const { createCanvas, loadImage } = require('canvas');
const fs = require('fs');

// 定义图片文件路径
const rasterImagePath = './data/image/raster.png';
const wktImagePath = './data/image/wkt.png';

// 创建一个新的 Canvas
const canvas = createCanvas();
const ctx = canvas.getContext('2d');

// 加载并绘制第一张图片（假设为 raster.png）
loadImage(rasterImagePath).then((rasterImage) => {
    // 设置 Canvas 的尺寸为第一张图片的尺寸
    canvas.width = rasterImage.width;
    canvas.height = rasterImage.height;

    // 将第一张图片绘制到 Canvas 上
    ctx.drawImage(rasterImage, 0, 0);

    // 加载并绘制第二张图片（假设为 wkt.png）
    loadImage(wktImagePath).then((wktImage) => {
        // 计算第二张图片在 Canvas 上的位置（居中）
        const centerX = (canvas.width - wktImage.width) / 2;
        const centerY = (canvas.height - wktImage.height) / 2;

        // 将第二张图片绘制到 Canvas 上
        ctx.drawImage(wktImage, centerX, centerY);

        // 将合成后的 Canvas 导出为 PNG 图片
        const outputFilePath = './data/image/output.png';
        const out = fs.createWriteStream(outputFilePath);
        const stream = canvas.createPNGStream();
        stream.pipe(out);
        out.on('finish', () => console.log('The PNG file was created.'));
    }).catch(err => {
        console.error('Error loading wkt.png:', err);
    });
}).catch(err => {
    console.error('Error loading raster.png:', err);
});