slice.js

var Canvas = require('canvas'),
    Image = Canvas.Image,
    fs = require('fs');

var w = 612;

var c = new Canvas(w, w);
var ctx = c.getContext('2d');

ctx.fillStyle = '#fff';
ctx.fillRect(0, 0, w, w);

var input = process.argv.slice(2);

var datas = input.map(function(i) {
    var img = new Image();
    img.src = fs.readFileSync(i);
    var ct = new Canvas(w, w);
    var ctxt = ct.getContext('2d');
    ctxt.drawImage(img, 0, 0, w, w);
    return ctxt.getImageData(0, 0, w, w);
});

function getpx(data, x, y) {
    var r = data[4 * ((y * w) + x) + 0],
        g = data[4 * ((y * w) + x) + 1],
        b = data[4 * ((y * w) + x) + 2];
   return [r, g, b];
}

for (var x = 0; x < 640; x += 1) {
    for (var y = 0; y < w; y += 1) {
        var px = getpx(datas[(Math.floor(x / 5) * 5) % datas.length].data, Math.round(x * (612 / 640)), y);
        ctx.fillStyle = 'rgb(' + px.join(',') + ')';
        ctx.fillRect(x, y, 1, 1);
    }
}

fs.writeFileSync('out_horiz.png', c.toBuffer());