color-transfer.js

const sharp = require('sharp');
const colorConvert = require('color-convert');

async function colorTransfer() {
    // 画像を読み込む
    const sourceImage = await sharp('./source.jpg').raw().toBuffer({ resolveWithObject: true });
    const targetImage = await sharp('./target.jpg').raw().toBuffer({ resolveWithObject: true });

    const { data: sourceData, info: sourceInfo } = sourceImage;
    const { data: targetData, info: targetInfo } = targetImage;

    if (sourceInfo.width !== targetInfo.width || sourceInfo.height !== targetInfo.height) {
        throw new Error('Source and target images must have the same dimensions');
    }

    const width = sourceInfo.width;
    const height = sourceInfo.height;
    const dstData = Buffer.alloc(sourceData.length);

    // RGBからLabへの変換
    const sourceLab = [];
    const targetLab = [];

    for (let i = 0; i < height; i++) {
        for (let j = 0; j < width; j++) {
            const offset = (i * width + j) * 3;
            const sourceR = sourceData[offset];
            const sourceG = sourceData[offset + 1];
            const sourceB = sourceData[offset + 2];
            const targetR = targetData[offset];
            const targetG = targetData[offset + 1];
            const targetB = targetData[offset + 2];

            sourceLab.push(colorConvert.rgb.lab([sourceR, sourceG, sourceB]));
            targetLab.push(colorConvert.rgb.lab([targetR, targetG, targetB]));
        }
    }

    // 平均値と標準偏差を計算
    const mean = { source: [0, 0, 0], target: [0, 0, 0] };
    const stddev = { source: [0, 0, 0], target: [0, 0, 0] };

    for (let i = 0; i < sourceLab.length; i++) {
        for (let c = 0; c < 3; c++) {
            mean.source[c] += sourceLab[i][c];
            mean.target[c] += targetLab[i][c];
        }
    }

    for (let c = 0; c < 3; c++) {
        mean.source[c] /= sourceLab.length;
        mean.target[c] /= targetLab.length;
    }

    for (let i = 0; i < sourceLab.length; i++) {
        for (let c = 0; c < 3; c++) {
            stddev.source[c] += Math.pow(sourceLab[i][c] - mean.source[c], 2);
            stddev.target[c] += Math.pow(targetLab[i][c] - mean.target[c], 2);
        }
    }

    for (let c = 0; c < 3; c++) {
        stddev.source[c] = Math.sqrt(stddev.source[c] / sourceLab.length);
        stddev.target[c] = Math.sqrt(stddev.target[c] / targetLab.length);
    }

    console.log('Source Mean:', mean.source);
    console.log('Source StdDev:', stddev.source);
    console.log('Target Mean:', mean.target);
    console.log('Target StdDev:', stddev.target);

    // 色変換の計算
    for (let i = 0; i < height; i++) {
        for (let j = 0; j < width; j++) {
            const offset = (i * width + j) * 3;
            const sourceIndex = i * width + j;

            const newLab = [
                ((sourceLab[sourceIndex][0] - mean.source[0]) * (stddev.target[0] / stddev.source[0])) + mean.target[0],
                ((sourceLab[sourceIndex][1] - mean.source[1]) * (stddev.target[1] / stddev.source[1])) + mean.target[1],
                ((sourceLab[sourceIndex][2] - mean.source[2]) * (stddev.target[2] / stddev.source[2])) + mean.target[2]
            ];

            const newRgb = colorConvert.lab.rgb(newLab);

            dstData[offset] = Math.min(255, Math.max(0, newRgb[0])); // R
            dstData[offset + 1] = Math.min(255, Math.max(0, newRgb[1])); // G
            dstData[offset + 2] = Math.min(255, Math.max(0, newRgb[2])); // B
        }
    }

    // 結果を保存
    await sharp(dstData, {
        raw: {
            width: width,
            height: height,
            channels: 3
        }
    }).toFile('./dst.png');
}

colorTransfer().catch(console.error);