Need to replace text plugin with one that uses native canvas text methods, but this works as POC

node_flot.js

console.log('flot init');
var document = require("jsdom").jsdom(),
    window = document.createWindow(),
    jQuery = require('jquery').create(window),
    fs = require('fs'),
    flot_location = 'http://jsno.de/javascripts/jquery.flot.svn.js',
    text_location = 'http://jsno.de/javascripts/jquery.flot.text.js';

window.Canvas = require('canvas');
loadScript(flot_location, function (){ loadScript(text_location, onPluginLoaded); });

function onPluginLoaded() 
{ 
    var data = getFlotData(),
        options = getFlotOptions(),
        placeholder = jQuery(''), // empty jQuery object
        plot = jQuery.plot(placeholder, data, options),
        node_canvas = plot.getCanvas(),
        img_dir = __dirname +'/public/images',
        img_name = 'flot.png',
        out = fs.createWriteStream(img_dir +'/'+ img_name),
        stream = node_canvas.createPNGStream();
    
    stream.on('data', function ( chunk ) {
        out.write(chunk); 
    });
};

function getFlotData()
{
    var d1 = [], d3 = [], d4 = [], d5 = [], d6 = [];
    var d2 = [[0, 3], [4, 8], [8, 5], [9, 13]];
    var i, l = 14;
    for (i = 0; i < l; i += 0.5) d1.push([i, Math.sin(i)]);
    for (i = 0; i < l; i += 0.5) d3.push([i, Math.cos(i)]);
    for (i = 0; i < l; i += 0.1) d4.push([i, Math.sqrt(i * 10)]);
    for (i = 0; i < l; i += 0.5) d5.push([i, Math.sqrt(i)]);
    for (i = 0; i < l; i += 0.5 + Math.random()) d6.push([i, Math.sqrt(2*i + Math.sin(i) + 5)]);
    
    var data = [
        { data: d1, label: "one", lines: { show: true, fill: true } },
        { data: d2, label: "two", bars: { show: true } },
        { data: d3, label: "three", points: { show: true } },
        { data: d4, label: "four", lines: { show: true } },
        { data: d5, label: "five", lines: { show: true }, points: { show: true } },
        { data: d6, label: "six", lines: { show: true, steps: true } }
    ];

    return data;
}

function getFlotOptions()
{
    var options = {
        width: 600, height: 300,
        xaxis: {labelWidth: 50, labelHeight: 20},
        yaxis: {labelWidth: 50, labelHeight: 20},
        grid: {
            backgroundColor: "#eee",   
            canvasText: {show: true, font: "sans 9px"},
            legend: {
                position: "sw",
                backgroundColor: "#de4",
                backgroundOpacity: 0.35
            }
        }
    };

    return options;
}

function loadScript( location, callback )
{
    var script = document.createElement("script");

    script.src = location;
    if (callback) script.onload = callback;
    document.head.appendChild(script);

    return script;
}